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Old 08-19-2014, 06:49 PM   #1
brian smith
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Default AMM 2.4ohms and running lean - makes sense?

The patient: '93 240, LH2.4 N.A.

Question:
Is an AMM diagnostic probe reading lower than specification consistent with running lean?

Symptoms:
- was illuminating the check engine light and storing 3 FI codes related to fuel mixture being incorrect
- this repeatably took 3 days of driving for enough learning to occur that made a noticeable difference in drivability that would end in the check engine light being illuminated
- cleared codes reappeared less than 5 seconds after restarting
- was running poorly when cold or wet, lots of stumbling below 2k, (ignition ignition ignition)
- primary and secondary ignition circuits checked, some weakness found on the secondary side, remedied and then FI memory cleared via battery disconnect
- will learn to idle (throttle switch closed) between 13:1 and 16:1 after 10 minutes or so, but starts out lean after clearing learned information
- has run at part throttle with the needle pegged at 17:1 for another day since battery disconnection and forgetting what it learned, but hasn't learned to go richer enough yet at part-throttle to run better and set the check engine light. Before resetting memory it would at least come off 17:1 and swing a bit for a few seconds while accelerating after gear changes.

Diagnostics:
- Air/Fuel gauge installed to produce the readings above, narrowband for now
- Before clearing the learned FI behaviors, it would run between 16:1 and 12:1 at WOT, throttle switch engaged (So no problem, right? )
- AMM terminal 2-3 measures 2.4 ohm instead of Bentley range of 2.5-4.0 ohm
- Fuel pressure perfect, new regulator and in-tank, very recently verified correct
- Vague inspection for vacuum leaks complete, no gaping holes or jigglable changes at idle
- Spark Plug gap was out of spec to the wide side, and before replacement the idle would stumble when the mixture swung to 12:1
- No codes stored nor CEL since clearing memory, but it's running very lean
- New Volvo-boxed CTS very recently installed and probed at the ECUs to verify good readings
- Load indicator lead from LH to EZ-K not yet checked

Basically, with the fairly expensive AMM reading 2.5% out of spec with an unknown tolerance on my measurement device, I'd like to be more confident that the AMM could indeed be causing this particular lean running symptom with this measurement across the leads.
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Old 08-19-2014, 08:17 PM   #2
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Just a quick post to get you on a new track. The spec for resistance was about the only thing the guys in the lab shop could come up with which an auto tech could measure, when working on the new LH models debuting in 1982 models.

The number measures the value of a reference film resistor which never goes bad, and can, in the bridge, be only be slightly affected slightly if the platinum wire breaks. No one has an ohmmeter accurate to those numbers, in that range, outside of an electronics lab.

The ohm reading on the AMM is bogus. As they say in NYC, faggetaboudit. They just needed something to put in the manual. The only other thing they could come up with was an ohmmeter check of the mixture pot on the pre-LH2.4 AMMs - another part which never craps out.

Sorry for the rant. I just cringe every time I read a post that says "my AMM reads 2.2 ohms does that mean its bad". The only way we have of determining an out-of-spec AMM is by substitution. Even using the at-rest voltage output is not definitive. Just find another AMM, and test it in your car BEFORE you think you might need one. We all should have at least one spare.
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Old 08-19-2014, 09:24 PM   #3
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Default new track / same track

Hmm...thanks for the info.
I think my "spare" that I'll be "finding" is the new factory one I've just ordered, since I don't have anyone around with a b230 at all to let me try theirs. Might look elsewhere before installing it if someone were to assert that the AMM needed to measure higher than spec resistance to make LH go lean so that maybe I could return it before using it...

It's good to know that even a reading within spec is not a guarantee that it's a good one, such that trying another is the honored diagnostic test.
I really haven't got another track at the moment other than giant unnoticed vacuum leaks, a new intake hose is on the way as well. All of these 80s and 90s eurocars with accordian-style hoses in the intake can have such hidden cracks that it's a shame someone didn't produce an alternative along the way...and I don't mean URO 1-yearos...
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Old 08-20-2014, 10:55 AM   #4
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Originally Posted by brian smith View Post
Hmm...thanks for the info.
Sorry, I feel like you must think I went off on you, but instead my frustration is in seeing this one-time shortcut mistake by Volvo Tech Pubs propagating so widely via the Chilton-Mitchell-Haynes-Bentley path causing people to needlessly spend big bux on air mass meters.

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I think my "spare" that I'll be "finding" is the new factory one I've just ordered, since I don't have anyone around with a b230 at all to let me try theirs. Might look elsewhere before installing it if someone were to assert that the AMM needed to measure higher than spec resistance to make LH go lean so that maybe I could return it before using it...
The advice I have given for 15 years is to procure an AMM and ECU used, as cheaply as possible, and test them in your own car (drive with them for some time) and keep them as reference spares to sub in when either is suspect. Like insurance. Cheap if planned; expensive if not. Still, you have the option of getting a used one from a fellow enthusiast, who has tested one in his car, if you need assurance the used one is "good."


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It's good to know that even a reading within spec is not a guarantee that it's a good one, such that trying another is the honored diagnostic test.
Nicely put. There are so many other components in the AMM which can degrade. A real test would require a bench setup with variable flow, humidity, and temp, done in an environmental chamber. This is what the remanufacturers should have, but as lousy as the reputation is, I suspect they don't.

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I really haven't got another track at the moment other than giant unnoticed vacuum leaks, a new intake hose is on the way as well.
Mostly I wonder at your AFR meter accuracy. The narrowband oxygen sensor is being analyzed by the chip in your ECU, which then almost instantly adjusts the injector opening duration, resulting in the switching your AFR meter is attempting to gauge. Any leak on the exhaust side will skew the info provided by the sensor. Any oil over the back of the sensor will alter the output too, as will a host of other maladies such as poor grounding through the exhaust components back to the fuel rail's bolts.

Short of it is I would put more value in observing the rate and duty cycle of your O2 sensor with a meter (or scope) than an aftermarket narrowband AFR meter, until you get more familiar with it. Have you been running the AFR meter before these codes popped up and their symptoms? Have a baseline? How recent is your sensor, and are you sure it is being heated? One year UROs. I like that. Now that is something we all seem to agree on -- URO rubber parts are lacking something in the formulation!

Speaking of a scope, I think that is what you would need to observe the load signal, or at least a duty-cycle setting on an equipped DMM. Maybe even my old-school dwell meter. Anyway that DC voltage figure Bentley shows is another example of test lab bogosity written toward the expected equipment to be found in an 80's Volvo dealership service bay.
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Old 08-20-2014, 12:59 PM   #5
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You can measure output voltage of the amm in a controlled lab chamber, but yeah, no real sure test for average joe other than swap the amm. With the 2.0 cars, I've been able to wave my hand over them and watch the output voltage change, and get a rough idea for that and the voltage a rest if they are "usable."

Ohm test the pot pre 2.4 or 2.4 amm resistor I've always found completely inconclusive and no help.

Lh2.0 and 1.0 are the only volvos ive found where the adjustment pot actually does anything significant.

If you can't find any vac leaks and the 02 works and switches quickly and responsively, and the engine is healthy otherwise and all cylinders have spark and fuel correctly and fuel pressure is good with no leaking fpr diaphragms, and no air is pulled in froma rotted intank pump transfer hose, it frequent that you swap the amm and all strange running returns to normal.

Hard to get one to burn cleanly as it should anymore.
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Old 08-20-2014, 01:06 PM   #6
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Originally Posted by cleanflametrap View Post
The only other thing they could come up with was an ohmmeter check of the mixture pot on the pre-LH2.4 AMMs - another part which never craps out.
this is OT, but I could show you a bad LH2.2 mix pot on a 007 AMM.
it caused me quite a lot of trouble.
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Old 08-20-2014, 01:10 PM   #7
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Oh yeh, there is a test for these AMMs that requires pulling back the boot and back probing, with everything connected along with using an oscilloscope, like as cleanflametrap mentions but that's all I recall.

Ah yes duty cycle. - I should have read more of the replies before posting.


Although maybe you could check it with a dwell meter?
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Old 08-20-2014, 03:57 PM   #8
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Originally Posted by Kjets On a Plane View Post
You can measure output voltage of the amm in a controlled lab chamber, but yeah, no real sure test for average joe other than swap the amm. With the 2.0 cars, I've been able to wave my hand over them and watch the output voltage change, and get a rough idea for that and the voltage a rest if they are "usable."
Absolutely! What I've found to be a hint is the rest voltage. This was a pretty reliable piece of info for me when investigating the -002 in LH2.0 cars. Now that all our cars are either LH2.4 or kjet, I have a nice selection of -016s to play with. For some time I've been suggesting a check of this output voltage with key on, motor off, with at least 1.4 and response to wafting air in front of the meter, but lately I see I can get a noticeable response > 500mV just by the squeezebox effect on the "accordion" tube. That way you don't have to mess with the plumbing to check it.

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this is OT, but I could show you a bad LH2.2 mix pot on a 007 AMM.
it caused me quite a lot of trouble.
Not off topic in my opinion. The topic is how to know if your AMM is good or bad. A very important topic to me and, I sense, a lot of us. Tell us all about your bad mixture pot. Moisture ingress? How did you prove it?

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Oh yeh, there is a test for these AMMs that requires pulling back the boot and back probing, with everything connected along with using an oscilloscope, like as cleanflametrap mentions but that's all I recall.
Sounds like you may have been reading up on "Mass Airflow Sensors." The homegrown US of A versions, called MAF sensors by most, are an improved design where communication with the ECU is concerned in that most have a voltage-to-frequency or PWM converter on board, eliminating the requirement our Bosch hot-wire meters have for excellent wiring between AMM and the A to D converter on the ECU's hybrid. Ours just use an air-mass to voltage curve with all the precision dependent on really good connections.
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Old 08-20-2014, 04:10 PM   #9
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I guess when you are talking about shortest possible time to knowing if the amm is good it varies from car to car, but I've never found any conclusive/consistently reliable test once you've exhausted everything else is eliminated for the amm other than swap it.

Unless you have the Bosch test lab and manufacturing facility in your back pocket, which tends to be a "no" for anyone but Bosch.

Unfortunate that it's largely impossible for any of us to really eliminate the amm using a tests like you can pretty reliably with most djet and kjet parts with pressure and volume measurements and a Dvom/scope, or as art states, things that would be available to someone Inge 80s and very readily available now.

On the bright side, there's lots of nice Bosch reman/exchange made in Germany or near brand new Amms out there, and of you have a clean vibration free environment without excessive heat for them, they seem to last well.

Why do you say all 2.4 or K-jet? The two highest production years for 240 (86/7) are 2.2 and usually what I seem to end up with. I'd love a good 82 mpg (of which I have a newish amm for and harness) or 83 Dl, but finding one in usable shape at this late hour is proving difficult.

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Old 08-20-2014, 05:21 PM   #10
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Originally Posted by Kjets On a Plane View Post
Why do you say all 2.4 or K-jet? The two highest production years for 240 (86/7) are 2.2 and usually what I seem to end up with.
Kind of dug out the one question in your reply... When I said
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Now that all our cars are either LH2.4 or kjet
I meant those 8 240's I care for. My interest is as a hobby with a family fleet, strictly amateur, not business.
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Old 08-21-2014, 04:10 PM   #11
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Originally Posted by cleanflametrap View Post
Not off topic in my opinion. The topic is how to know if your AMM is good or bad. A very important topic to me and, I sense, a lot of us. Tell us all about your bad mixture pot. Moisture ingress? How did you prove it?



Sounds like you may have been reading up on "Mass Airflow Sensors." The homegrown US of A versions, called MAF sensors by most, are an improved design where communication with the ECU is concerned in that most have a voltage-to-frequency or PWM converter on board, eliminating the requirement our Bosch hot-wire meters have for excellent wiring between AMM and the A to D converter on the ECU's hybrid. Ours just use an air-mass to voltage curve with all the precision dependent on really good connections.

I'm not sure, the pot reads very low and sometimes all over the place. (like 0.16 to 0.60 in a quarter turn) I'd probably have to send it to you for you to see what it does.

My best method was putting my 5 007s all next to each other and checking each pin combination until I found a group with similar readings to form a baseline. From that point I was able to diagnose which units worked and which wouldn't from the DMM readings. Now I have two spares I keep in the cab along with the one installed, and two dead I keep in a box in case I can ever figure out how to fix them.


The main dead 007 with the pot reading issue from above was subject to a very bad failing harness.
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Old 08-21-2014, 04:58 PM   #12
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Originally Posted by 1choice View Post
I'm not sure, the pot reads very low and sometimes all over the place. (like 0.16 to 0.60 in a quarter turn) I'd probably have to send it to you for you to see what it does.

My best method was putting my 5 007s all next to each other and checking each pin combination until I found a group with similar readings to form a baseline. From that point I was able to diagnose which units worked and which wouldn't from the DMM readings. Now I have two spares I keep in the cab along with the one installed, and two dead I keep in a box in case I can ever figure out how to fix them.


The main dead 007 with the pot reading issue from above was subject to a very bad failing harness.
That pot actually has nothing to do with the Air Mass Meter. It allows you to set the mixture from under the hood (where the time-honored practice of mixture adjusting has been made) but the actual function is to set a voltage the ECU reads to adjust its response to the AMM's output. IOW, you could just mount that pot inside the car next to your AFR meter, if you have one, wiring it directly to the ECU.

Another tip on the mixture adjustment... Since there's no dial or other reference to where you set it, folks pull the plug on the AMM and check the resistance. There are lots of anecdotes floating around the forums quoting a particular resistance as a good starting point for mixture setting. It is easier, more accurate and repeatable, and less intrusive to just measure the voltage on the mixture wire -- backprobe pin 6 on the -007; a yellow wire in the 240.

Years ago when the LH2.0 cars were still plentiful in the Rust Belt yards, I'd take a bag phone battery with me. I'd use it, with a scrap of harness, to power up the AMM and measure its static output, as a hopeful indicator of its state of deterioration. This was because our yards charged $45 for one AMM and no returns accepted.

The -002, unlike the -007, could have its offset adjustment change off of the hybrid, so I was able to restore operation to a couple units which had fallen too lean to compensate at the ECU.





But the -007 is not so conveniently constructed.
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Old 08-21-2014, 09:43 PM   #13
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Originally Posted by cleanflametrap
Sorry, I feel like you must think I went off on you, but instead my frustration is in seeing this one-time shortcut mistake by Volvo Tech Pubs propagating so widely via the Chilton-Mitchell-Haynes-Bentley path causing people to needlessly spend big bux on air mass meters.
No animosity interpreted, the comment was favorably received, so really, thanks.

Quote:
Originally Posted by cleanflametrap
Mostly I wonder at your AFR meter accuracy. The narrowband oxygen sensor is being analyzed by the chip in your ECU, which then almost instantly adjusts the injector opening duration, resulting in the switching your AFR meter is attempting to gauge. Any leak on the exhaust side will skew the info provided by the sensor. Any oil over the back of the sensor will alter the output too, as will a host of other maladies such as poor grounding through the exhaust components back to the fuel rail's bolts.
Upon key-on, the AFR meter indicates 14.7. Watching the sensor during the first few second of a running engine displays a slow climb toward rich mixtures while the sensor is being heated. The O2 sensor is under 1000 miles old, and any exhaust leaks are aft of the sensor. The fuel rail bolts have been replaced by stainless studs installed with dielectric grease, stainless washers between them and stainless nuts, and an additional ground lead from the fuel rail studs to the battery negative bus has been added. I haven't got any oil on the exhaust system. AFR meter accuracy may be an issue, but since the ECU is working hard with the throttle switch closed to attain something near 14.7, I don't think that it's, say, 50% inaccurate.

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Originally Posted by cleanflametrap
Short of it is I would put more value in observing the rate and duty cycle of your O2 sensor with a meter (or scope) than an aftermarket narrowband AFR meter, until you get more familiar with it. Have you been running the AFR meter before these codes popped up and their symptoms? Have a baseline? How recent is your sensor, and are you sure it is being heated? One year UROs. I like that. Now that is something we all seem to agree on -- URO rubber parts are lacking something in the formulation!
The AFR meter is newly added, and I'm not well familiarized with it yet. The differences before and after clearing the memory are substantial. I ran it before clearing the memory for enough days and operating conditions to be confident that the different readings are due to actually reading something different and not just randomness in the sensor/gauge interactions.

Quote:
Originally Posted by cleanflametrap
Speaking of a scope, I think that is what you would need to observe the load signal, or at least a duty-cycle setting on an equipped DMM. Maybe even my old-school dwell meter. Anyway that DC voltage figure Bentley shows is another example of test lab bogosity written toward the expected equipment to be found in an 80's Volvo dealership service bay.
At idle, the duty cycle is about 1.5-2.5 seconds on the meter. Under the right conditions which can produce a reading other than pegged at 17:1, a 1500rpm throttle hold in neutral increases the frequency to under 1 second. This seems to hold from there on up through the rev range. Timing throttle opening blips to the richer or neutral mixture conditions yields a beneficial effect on driveability. Letting the clutch out to move the car from idle when the AFR swings to 17 causes annoying stumbles 100% of the time. My impression is that although the gauge may be imprecise, that it is at least accurate. It really seems that at idle things work as intended, but that the computer can't get it anywhere close to correct at any other time unless I've just let off the throttle and the mixture then swings up past 14.7:1 for one cycle, then fuel cut, then a second or so after sitting against the throttle stop starts to swing back toward healthy mixture oscillation at idle.

After a couple more days of driving, the computer has not stored a code yet, nor has it learned as well as it previously did to get richer at part throttle. Tomorrow, I hope, the new AMM arrives. I think that before my secondary ignition circuits work, I would have seen a code by this point; it would stumble at 12:1 before, while it now will continue to fire smoothly, so perhaps the learning process is a bit slower without the misfires. Seems tough to call it much of an improvement, I'd rather drive with the darn yellow light on and +5 lb-ft below 2k than have no light and feel like someone added 1/2 inch to my throttle cable length.

Thanks for the ideas so far though!
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Old 08-21-2014, 11:06 PM   #14
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Upon key-on, the AFR meter indicates 14.7. Watching the sensor during the first few second of a running engine displays a slow climb toward rich mixtures while the sensor is being heated.
That behavior I recognize, as the 0.5V that corresponds to stoich on the meter comes from the ECU before the sensor warms enough to produce its own. Now, when it rises toward rich, in my cars (B230F 240s) in the summer, the sensor begins switching around 30-40 seconds after cold start. Does your AFR meter average over time (integrate the duty cycle) or interpret the voltage excursions (respond rapidly)? Either way, after reading the rest of what you wrote, I am no longer "wondering" about the accuracy of your mixture reports.


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The O2 sensor is under 1000 miles old, and any exhaust leaks are aft of the sensor.
Probably an impertinent comment at this point, but I have heard it explained to me that leaks past the sensor do indeed affect it. Just heard, mind you, no experience or experiment here. But I don't suppose you have the pipe just hanging in the air past the cat.


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The fuel rail bolts have been replaced by stainless studs installed with dielectric grease, stainless washers between them and stainless nuts, and an additional ground lead from the fuel rail studs to the battery negative bus has been added. I haven't got any oil on the exhaust system.
Wow!


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AFR meter accuracy may be an issue, but since the ECU is working hard with the throttle switch closed to attain something near 14.7, I don't think that it's, say, 50% inaccurate.
I agree. When you say the ECU is working hard, do you mean the AFR tends to pull lean at idle periodically, as if the ECU is adjusting for an edge-of-range condition? This really does sound like the air is not being measured properly. Sorry to be Capt. Obvious here, but I think that is what you are trying to tell us!


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The AFR meter is newly added, and I'm not well familiarized with it yet. The differences before and after clearing the memory are substantial. I ran it before clearing the memory for enough days and operating conditions to be confident that the different readings are due to actually reading something different and not just randomness in the sensor/gauge interactions.
I've read and re-read this paragraph. I know you are saying encouraging things about trusting the AFR meter, but I'm hung up on the ECU reset (clearing memory) idea and whether you are relieved of the horrible lean running when the ECU finally sets the limp home injector duration, which I assume is accompanied by a 113 and CEL. That's when the AFR meter should waggle with load and stay generally rich, I think. The oxygen sensor, by your description, is telling the truth. Pulling the plugs would be somewhat of a verification, but given your fuel rail grounding attention, I would again assume you have a nice new intake manifold gasket, and know for certain all four injectors are doing their jobs.

As much as you've done without a swap AMM, I have a lot of hope you'll be happy with that replacement tomorrow.


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My impression is that although the gauge may be imprecise, that it is at least accurate. It really seems that at idle things work as intended, but that the computer can't get it anywhere close to correct at any other time unless I've just let off the throttle and the mixture then swings up past 14.7:1 for one cycle, then fuel cut, then a second or so after sitting against the throttle stop starts to swing back toward healthy mixture oscillation at idle.
If you let it idle after the fuel cut on decel, does the AFR show you mixture slowly walking away in the lean direction again? Do you get the 232 fuel code often?

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After a couple more days of driving, the computer has not stored a code yet, nor has it learned as well as it previously did to get richer at part throttle. Tomorrow, I hope, the new AMM arrives. I think that before my secondary ignition circuits work, I would have seen a code by this point; it would stumble at 12:1 before, while it now will continue to fire smoothly, so perhaps the learning process is a bit slower without the misfires. Seems tough to call it much of an improvement, I'd rather drive with the darn yellow light on and +5 lb-ft below 2k than have no light and feel like someone added 1/2 inch to my throttle cable length.
So I'm reading here you did a tune-up? New plugs, wires, rotor, cap? Was this long into the onset of the driveability being in the dumper? Just a hunch I had a long time ago, when I discovered a coil wire support clip holding it to a brake line. At that point I recalled having a problem with an AMM on a car without that, and having discovered the resistor in the rotor was wide open. It would run with the spark jumping the gap, but the coil wire must have been reaching some pretty high voltage with all that extra gap in the secondary wiring, and guess what that coil wire lays on, when there's no support clip? Just an idea, and that wasn't an 016 AMM either.
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Old 08-23-2014, 12:30 PM   #15
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Well, after another pair of parts, the patient is healthy, responsive, and free of bad symptoms.
I found one tiny hole in the plastic hose between the AMM and the throttle body when replacing it with a new one. Hose replacement had produced no change in symptoms; still very sick.
The Volvo-box reman. AMM on the other hand was the magic.
Upon the next restart, the engine was able to run within a decent 16:1 to 12:1 range before even getting warmed up with the throttle cracked open to reach around 1500-2000rpm in neutral. This was the first time it's been able to do that since the gauge was installed.
As a second test, I then disconnected the battery terminal for 20 min to reset the ECU, and upon reconnection and starting the car it was able to heat the O2 sensor, go into closed-loop operation, and maintain decent AFR both at idle and at part-throttle, all before having any time to "learn."

To answer some questions from the last post, and maybe for posterity, here is a partial restatement of the symptoms and resolutions:
From an ECU reset, the car would struggle to idle when wet or cold, with a smell of fuel in the exhaust. Whether this was due to an over-rich condition or the misfires I was uncertain.
After about 3 days of driving, the computer would light the CEL and store 2-3-1, 2-3-2, and 2-2-1 (the only one triggering the CEL.)
"Fuel system compensating for extremely rich or extremely lean air/fuel mixture" as a description was not instructive enough for me.
Air/Fuel mixture gauge was installed (after much testing, improvement of fuel pressure, and not much change in operation)
Idle misfire was found to coincide with idling O2 sensor swings to the 12:1 rich range
Ignition wires tested to be within range, cap/rotor corrosion knocked off, plugs replaced and 3 of 4 found old plugs to have grown to over 0.032" plug gap.
Misfire at idle solved by these secondary ignition circuit remedies.
After a few days of driving and familiarizing myself with the AFM gauge readings, I reset the ECU.
After the reset, no more codes were stored nor CEL, but there was failure to achieve decent AFR at any throttle position other than on the idle stop. This performance maintained for days of driving, and the ECU didn't seem to learn to go as rich as it previously did with the misfires - perhaps there was no learning before either, simply more unburnt fuel duel to misfires. Fuel economy wasn't horrible enough to suggest this (26.1mpg, I'm used to seeing 25-27.)
Testing the pair of terminals recommended as the Bentley test for bad AMM was too close for me to call: 2.4 ohms on a specified range of 2.5-4.0 ohms. I know that I saw a 2.5 ohm reading a couple of months ago when I first started battling these same stored codes.
In this case, replacing the AMM was immediately a full cure for all of the bad symptoms I'd seen. It was not my first stop, and everywhere else I looked along the way I found things that were either bad or at the edge of their acceptable ranges. A better test for an AMM might have stopped me from the new parts parade of a new in-tank pump, a new FPR, a new O2 sensor, new fuel injectors, an air/fuel gauge, ignition amplifier and terminal plug, spark plugs, CTS, FI terminals and supplemental ground lead. The $300 Air/Fuel gauge being installed first may have saved a number of stops along the way as well. Being around the cost of a new AMM, and useful in diagnostics henceforth, I might suggest that item as an additional tool to anyone who hasn't got a known-good used AMM for diagnosis.

Now for some motoring miles...from stalls, stumbles, and poor engine response, I'm free at last!
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Old 08-25-2014, 12:57 PM   #16
cleanflametrap
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Originally Posted by brian smith View Post
The Volvo-box reman. AMM on the other hand was the magic.
Magic is right.

Because there is no better test of the AMM, I still believe you are maybe about $50 shy of free at last. My advice is, if you plan to keep the car, you find another AMM to put on your shelf. Give it a couple days in the car as a test.
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