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Old 07-16-2019, 09:44 AM   #1
240-FAN
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Default Whelp! '91 244 seems to have the chills (shudders!)

Last year, I did a major (for someone of my skill level) project on my '91 244. A lot of you on here chimed in and helped me along in getting my car back together

By the time I had the car buttoned up, I could only drive it for a week, maybe two before she went into winter storage. During that time, the car would stutter and stumble and struggle to accelerate. During that time, I refilled my gas from less than half a tank to full and it seemed to make the problem go away. Based on what I read in older threads, that typically meant the in-tank pump is dead or about to be dead.

I finally got her out and this past weekend drove about 230 miles without any problems. Drove her right till the gas gage was just above "E" and no issues. Filled her up at Costco (where I've been filling up for years) and within about 20 miles of the fill up, same issues.

Bucking, shuddering. Weak acceleration. No CEL up until this point. Pulled the car into a lot, shut her off and unplugged the AMM. She started but shuddered and then eventually evened out. I decided to drive a 1-2 miles like that to back home. About 0.75miles away from home, the stumbling became really bad and I pulled over to the side and shut the car off. It smelt like the car was running lean. I say running lean, because, it didn't smell like gas (which I understand is an indication of it running rich). Au contraire, it smelt mildly burnt.

Plugged the AMM back in and didn't clear the CEL. Drove the car about 7-8 miles since then and it runs fine. However, I cannot clear the CEL.

OBD I codes that are present:
1. 1-2-1
2. 3-2-2

Does this mean that I had a failing AMM and that unplugging it was the final straw?

Side note: For the past year or so, the car would need to be cranked longer on a hot day after it had been driven and it hesitate some before it would have a smooth idle. This specific behavior was present before I did all the work on the car. FPR is a new Bosch unit from last year. 4 plugs, 3 wires (I f'ed up one while doing it) and distributor were new as of 20K miles ago.

Last edited by 240-FAN; 07-16-2019 at 09:49 AM..
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Old 07-19-2019, 01:33 PM   #2
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Anyone?
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Old 07-19-2019, 02:16 PM   #3
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Define the codes.
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Old 07-19-2019, 02:23 PM   #4
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ooops...here they are:
1-2-1 – Mass air flow meter signal faulty or missing
3-2-2 – Mass Air Flow sensor burn-off signal missing or faulty (MAF wiring fault)
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Old 07-19-2019, 03:27 PM   #5
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Looks like an MAF to me. If you've got a "known good" local to you that you could try, that would be good.

Also, and not related, stop buying the cheapest gas you can find.

https://www.toptiergas.com/
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Old 07-19-2019, 03:35 PM   #6
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Inspect the terminals for corrosion.

Make a tool with spare male pins from a donor MAF and "drag test" the female terminals for looseness.

Confirm power and ground, or skip to below test.

Maybe put a meter on the signal wire (backprobe) and monitor the voltage. Tap on the meter and see if you can get it to glitch.

Or just try another one.
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Old 07-19-2019, 03:37 PM   #7
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I don't have a used MAF, I was going to post in the wanted section under classifieds once that seemed to be the consensus here. My family has been filling up the gas at that Costco for years. They are toptier and cheap. Most other gas stations in the area don't have the top tier sticker on their pumps.
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Old 07-19-2019, 03:40 PM   #8
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Quote:
Originally Posted by ZVOLV View Post
Inspect the terminals for corrosion.

Make a tool with spare male pins from a donor MAF and "drag test" the female terminals for looseness.

Confirm power and ground, or skip to below test.

Maybe put a meter on the signal wire (backprobe) and monitor the voltage. Tap on the meter and see if you can get it to glitch.

Or just try another one.
The second test you list - would you happen to know which wires are what in the connector?
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Old 07-19-2019, 03:59 PM   #9
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Nope. Refer to a wiring diagram. These old Volvos don't have problems with the terminals like modern cars, but it can happen. Red/white is signal, I think. Blue yellow is power.

I had a car recently with and intermittent electrical issue and it was poor terminal tension. I have access to the correct special tools for front probing female terminals for testing the circuit and also for checking for proper terminal tension.
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Old 07-19-2019, 11:47 PM   #10
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Well I'll be damned.
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Old 07-21-2019, 03:10 AM   #11
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Quote:
Originally Posted by 240-FAN View Post
Bucking, shuddering. Weak acceleration. No CEL up until this point.

Pulled the car into a lot, shut her off and unplugged the AMM. She started but shuddered and then eventually evened out. I decided to drive a 1-2 miles like that to back home. About 0.75miles away from home, the stumbling became really bad and I pulled over to the side and shut the car off. It smelt like the car was running lean. I say running lean, because, it didn't smell like gas (which I understand is an indication of it running rich). Au contraire, it smelt mildly burnt.

Plugged the AMM back in and didn't clear the CEL. Drove the car about 7-8 miles since then and it runs fine. However, I cannot clear the CEL.
.
Unclear narrative.
getting AMM codes after running with it unplugged is not unexpected.
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Old 07-21-2019, 10:52 AM   #12
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I guess what I was trying to state in my original post was that after plugging the MAF/AMM back in, I did the reset procedure for the OBD port and I continue to get the 2 error codes listed above.

I’ve unplugged the MAF before (like a year and a half ago) and I was able to reset the CEL by following the procedure, thereby making it go away.
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Old 08-23-2019, 06:20 PM   #13
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Swapped the MAF with a known good unit. Problem persists.
Verified both pumps work. Air filter is clogged but will be remedied tomorrow or day after.

Took this opportunity to clean the throttle body, flame trap and IAC. Nothing was particularly dirty or gunky. Still stumbles and is very very apparent when I try to take off from a stop sign.

Definitely more apparent when the engine is warmed up to operating temperature.
The car also struggles to start on very hot days even if it’s been parked for hours.

What do I check next? The in tank pump is an airtex unit that was replaced in 2012.
The sender was in really bad condition and I JB welded the top flat portion of it back then because of how bad the rust was.
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Old 08-23-2019, 06:53 PM   #14
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Can you test the fuel pressure?
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Old 08-23-2019, 07:48 PM   #15
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Quote:
Originally Posted by 240-FAN View Post
Swapped the MAF with a known good unit. Problem persists.
Verified both pumps work. Air filter is clogged but will be remedied tomorrow or day after.

Took this opportunity to clean the throttle body, flame trap and IAC. Nothing was particularly dirty or gunky. Still stumbles and is very very apparent when I try to take off from a stop sign.

Definitely more apparent when the engine is warmed up to operating temperature.
The car also struggles to start on very hot days even if itís been parked for hours.

What do I check next? The in tank pump is an airtex unit that was replaced in 2012.
The sender was in really bad condition and I JB welded the top flat portion of it back then because of how bad the rust was.
FWIW, consider buying a genuine volvo/bosch unit. Had similar symptoms on my 84 DL, replaced with a "good rebuilt unit". Problems persisted. Replaced AMM with genuine OE and fixed the problem. YMMV
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Old 08-23-2019, 08:08 PM   #16
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Quote:
Originally Posted by ogamer777 View Post
FWIW, consider buying a genuine volvo/bosch unit. Had similar symptoms on my 84 DL, replaced with a "good rebuilt unit". Problems persisted. Replaced AMM with genuine OE and fixed the problem. YMMV
Yep. Itís a used Bosch 016 that came off a memberís vehicle on here.

Interestingly, I took it for a drive. Ran fine. Turned car off, ran inside for a few mins.
Came back and turned the car on to park, and it SURGED. My cheap-0 tach showed 540ish to 900ish for a few seconds and the voltmeter was swinging wildly as well.

Iím seriously lost on this!!!!
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Old 08-23-2019, 08:10 PM   #17
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Quote:
Originally Posted by rb92673 View Post
Can you test the fuel pressure?
How does one go about doing this? I have never done it before.
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Old 08-23-2019, 09:40 PM   #18
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Old 08-23-2019, 11:16 PM   #19
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When was the last time the spark plugs were replaced and verified to have the proper gap? .028"
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Old 08-24-2019, 09:01 AM   #20
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Check the plug on the AMM cable, IIRC, make sure all the contacts look the same and are at the same depth, the can get pushed in or spread so they don't make good contact. This could explain why swapping the part doesn't help.
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Old 08-24-2019, 11:12 AM   #21
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^^
Also, if the rubber boot on the connector is torn, look for evidence water has gotten in. This pic of some LH2.0 AMM pins is about 20 years old -- one of the first lessons I learned about how critical contact resistance is in the power, ground, and output circuits for the air mass meter.



Another thing you may want to have a look at is the harness wiring for the grounds made at the fuel rail. The wiring is spliced under the vinyl sheathing. Several examples come to mind where those splices were compromised by moisture.

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Last edited by cleanflametrap; 08-24-2019 at 11:46 AM.. Reason: Included the stuff about the power and signal grounds at the fuel rail bolts
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Old 08-24-2019, 08:37 PM   #22
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Did you do the tests I mentioned?
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Old 08-26-2019, 06:25 PM   #23
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Air filter swapped, the old one was in pretty bad shape.
Inspected the terminals on the MAF connector and all 5 of them look fine.

Plugs were changed 20k miles ago. They haven’t been touched since

Next step is to check the grounds as Art suggested.
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Old 08-27-2019, 06:06 PM   #24
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You gotta check terminal tension at the MAF and ECU. Make a tool.

Check continuity between the ECU and MAF circuit/s.

Do a loaded voltage drop on the ECU ground circuit.


Have you checked the voltage output of the MAF yet?

Last edited by ZVOLV; 08-27-2019 at 11:17 PM..
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Old 08-28-2019, 07:56 PM   #25
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I did not. Would you happen to know which pin corresponds to what on the MAF?
I tried a google search for 1991 Volvo 240 wiring diagrams and it didnít result in much....

Volvotips is what Iíve used in the past and I canít get anything on there to load.
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