940 running way too rich

Car-
Volvo 95 940 wagon b230ft aw71
Mods-
T3/t4 turbo custom made tubular header 38mm emusa wastegate 012 maf 440cc injectors turbotankshane chips ezk/Ecu hks blowoff valve mat is post intercooler dw200 plx afr
Problem-
The other day while making a pull I heard a slight popping sound and normally I have blown off an intercooler pipe.....when this happens my car goes pig rich. Upon further inspection no intercooler tubing was out of place, all clamps were tight. But my car was still running super rich....like 10 at idle and 11s when cruising. I pressure tested the intercooler tubing and all was well. Next swaping these parts with know good ones. Plugs, plug wires , maf, fpr, injectors and Ecu and ezk. Any suggestions would be greatly appreciated!

Thanks
Luke

Check coolant temperature sensor voltage at the computer. This will let you check harness and sensor at the same time, look in green books for spec. You can make sure it's plugged in first too, if it's not connected it will run uber rich.

The voltage and resistance check out....thanks for the thought!!

A little more info....when the car is first started it is at 14.7 and over about 20 seconds it richness itself up to under 10. Anyway it could be iac related?? I just wouldn't see afrs being that far off. I took a 02 sensor and plugged it in outside of the downpipe and nothing changed...which leads me to believe it is in some sort of limp mode or it isn't taking feedback from the o2 at all...I'm baffled ��

lbd94ta said:

A little more info....when the car is first started it is at 14.7 and over about 20 seconds it richness itself up to under 10. Anyway it could be iac related?? I just wouldn't see afrs being that far off. I took a 02 sensor and plugged it in outside of the downpipe and nothing changed...which leads me to believe it is in some sort of limp mode or it isn't taking feedback from the o2 at all...I'm baffled ��

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Unplug the iac, that will tell you if that's the culprit.

Fuel Pressure Regulator?

When I unplug the iac it stumbles and almost dies....but when I plug it back in here is no change....like the rpms drop when unplugged but when plugged back in they stay the same. The fpr has been switched with a known good one.....maybe the return line is clogged??? I'm gonna check fuel pressure when I get off work! Thanks for the help!!!!!

Fuel pressure is spot on.....still stumped

The only way I can get the afr gauge off of 10.0 is to unplug a spark plug wire....which baffles me. I figured by cutting the spark to one cylinder would cause the fuel to pass straight through to the exhaust causing an even richer condition. It is exactly te opposite...the afrs go to 11.4 strange....

lbd94ta said:

The only way I can get the afr gauge off of 10.0 is to unplug a spark plug wire....which baffles me. I figured by cutting the spark to one cylinder would cause the fuel to pass straight through to the exhaust causing an even richer condition. It is exactly te opposite...the afrs go to 11.4 strange....

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A misfire will typically read lean, I believe. The O2 sensor detects... well, the amount of O2 in the exhaust. If you are down a cylinder (due to having unplugged one of the spark plugs, for example), the mixture drawn into that cylinder isn't getting burned, effectively pumping air (and fuel, but the sensor doesn't detect that) into your exhaust.

As for what could be causing your problem, that definitely does sound like a limp mode. Have you tried swapping out the MAF? If the filament is damaged or extremely filthy it will make the engine run all kinds of bonkers. You can test it by unplugging it while the car is running; if nothing changes, you have a bad MAF. If not that, have you tried swapping the ECU? I don't know what happens when they cack out, but a persistent lean condition doesn't seem unreasonable.

I have tried unplugging the maf and the car stalls......I also switched it with a 016 in a 3" housing(my back up maf) to no avail. I have switched injecors and ecus twice. 660cc with appropriate Ecu, 440cc with tlao chips, and a stock Ecu with stock injectors with the same results every time......

Run a test from the PLX for the O2 sensor and see how healthy it is. Other than your readings, how is the car running?

EDIT
Are you running a stock O2 and the wideband O2 or using the wideband for both?

Did you check the knock sensor? If it is damaged maybe the ECU detects a knock signal and the LH will run a richer mixture.

Dumb question: you're still making boost, right? What is your boost pressure compared to what it was prior to the "popping" incident? If you are losing your boost pressure for some reason, that could totally explain the rich running condition. Maybe your wastegate or showoff valve is jammed open or something? Or your turbo just seized? Is your boost controller ****ed up?

MrBrown said:

Other than your readings, how is the car running?

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Yeah, what else is it doing? Is it driveable? If so, is it exhibiting any other signs of running super rich (bogging, sooty plugs, smokey or rich-smelling exhaust, terrible mileage, lack of power, etc.) aside from the wideband reading? I suppose it could just be a faulty wideband, although it seems a little unlikely that it would be producing a consistent reading at all in that case.

Assuming the O2 sensor is working properly, and assuming you boost pressure is where it should be, the fact that your AFR starts out near 14.7 when you first start the car and starts running richer over a few seconds kinda sounds like a faulty temperature sensor or something. Does it follow the same pattern if the car is already warmed up, or just when you start it cold? For instance, if the car is warmed up and running at an AFR of 10 or so and you shut it off, what happens when you start it up again? Does the AFR immediately jump back to 10, or does it start at 14.7 and gradually drop back to 10? If the AFR seems to be dependent on the coolant temperature (as in, it only runs correctly when the engine is cold), that seems to point at a temperature sensor malfunction of some kind. If it is dependent on how long the car has been running (as in, it runs correctly for a few seconds every time you power-cycle the ignition, regardless of engine temperature), then you have something else going on.

Just spitballing a few other things to check here:
What does your wiring harness look like? Is it in decent condition, or is it 80's Volvo crusty? Shorts can cause all sorts of weirdness.

You said this started after you heard a popping sound when you were "making a pull" right? What did the popping sound like? Did it make a repeated popping, or did it just do a single pop and start running like crap? Was it doing anything strange prior to that happening?

Have you changed anything else on the car recently?

Again, if it's not making boost, that is definitely your problem. Your system is set up for dumping fuel into an engine with significantly more air flowing through it than an NA redblock would have, so if you aren't making boost, it would run mad rich.

Mrbrown I run the stock o2 to the Ecu and the plz is just to monitor things....I use to run the signal wire from the plz to the Ecu but lh really didn't like it.

Fjergus boost pressure is the same....I have pressure tested the piping. Believe it or not my eBay turbo is still spinning freely....I have a good manual boost controller...holds boost rock solid. It is not driveable....unless 10.2 at cruising is acceptable! Hahah it is pouring black smoke with an extreme lack of power....it will barley idle. Now that I think about it the gauge always starts at 14.7 and takes 5 sec to warm up so it might be fully rich at star up too. It has the same result when started hot or cold....I tested the ect sensor at the Ecu and it is within spec. Harness looks great! 95 car with no rust! One single pop right close to the limiter in second....on decel the gauge went to 11 and has stayed really close ever since. Befor the pop it was running like a raped ape.... thanks for all of your suggestions this has really got me stumped ��

Look real hard at the rubber boost connections, as in remove them and look inside. I had one that had split inside, it wasn't visible from the outside.

Vb242 I pressure tested the tubing up to like 35 psi.....I only run 25

Huh. What do the plugs look like? Are they consistent, or is one of them significantly nastier than the others? Maybe one of your injectors stuck open or something bizarre like that. What about the knock sensor? Someone already mentioned that, but I didn't see if you checked it or not. I don't think that would cause it to very consistently run super rich, but I suppose it might.

What did the pop sound like, and where did it sound like it was coming from? Have you checked your timing? I wouldn't think it would run rich if your timing belt jumped a tooth or something, but I don't know for sure. What about your ignition timing? Jacked up ignition timing could indicate that the ECU thinks your engine is knocking like mad and is retarding the timing as a result.

Oh, and check the wiring to your throttle position sensor. I had it short out on my LH2.2, and it ran incredibly badly until I figured it out. In my case, it caused a lean condition at full throttle (because the ECU though I was at 0% throttle instead, and cut the fuel accordingly), but it might do some other weirdness if it failed in a different way.

I dunno though, that's a weird one. I'm inclined to think it's something electrical, but you've already verified most of the electrical system. What about other sensors? The limp-home mode hypothesis seems reasonable, so maybe look into what can trigger that. What about a bad crank position sensor? I would think it would die entirely, but I haven't played with an LH2.4 car.

Multi channel scope and graph MAF voltage, o2 sensor voltage, and fuel injector pulse width might show the issue.

Following, as I have a similar issue. Similar deal, did a pull, no pop sound, seemed fine, ran ****ty & lean, got gas, now runs rich 12-13.5 cruise, 10 as soon as I hit positive pressure, boost sys pressure checked, ect sensor replaced, although my idle is hunting even though the sensor reads fine. Running stock turbo @13psi, 60lb deka injectors(I know they're too big but it should mostly compensate), hks bov, 012 maf

Update: cleaned MAF, huge improvement, now questioning injector size