[jcasaccio]

There are a ton of posts on these 2 codes (also referred to as e3 and e4 codes from BavAuto/Peak reader). They pop up after 5-150 or so miles of driving, once I clear them (BavAuto reader). I am replacing parts and then driving the emissions readiness cycles and they come back. This is making me crazy and I will not pass emissions until I figure this out.

I bought the car knowing this was a recurring issue - PPI and previous owner stated...

1996 E36 M3. 43k on it when I bought it. Now has 52k. Car runs great and pulls hard, runs smooth. Did stumble first 5 seconds on cold start, but that is better since cleaning the ICV....

Within last 10k miles have receipts from previous owner replacing:

• entire cooling system replaced - aluminum radiator, water pump (metal impeller), electric fan conversion, hoses, thermostat, temp sensor
• Intake and valve cover gaskets (kit with all O-rings as well)
• New plugs
• Both pre cat O2 sensors (BMW part 11-78-1-427-884)
• MAF - BMW part, not a knock off (BMW part 13-62-1-703-275)
• smoke tested - no leaks
• fuel pressure tested fine

I just replaced last week:

• fuel filter
• CCV including o-ring, all hoses
• Dipstick o-ring
• tested SAP, valve and solenoid - functions as designed no leaks or exhaust backpressure. Pump works fine during cold start (runs couple mins). vacuum from valve and solenoid is strong and does open the egr valve as designed. Valve does not leak exhaust when vacuum is or is not applied, but opens and allows pump air to enter as needed.
• cleaned ICV and replaced hose and o-ring gasket
• brake booster to manifold hose is tight and not cracked
• sprayed carb cleaner along valve cover and intake manifold checking for air leaks - no changes in idle or stft numbers.

Seems to be after highway driving. I am hoping this is not some microscopic leak that flares up only higher RPM, as I cannot find it...

I did hook up an OBDII reader to check trims and O2 voltage at idle:

• Precat sensor voltage bounces up from 0-1V, I think this is normal
• O2 % on bank 1 and 2 bounces between -1.5 to about 4 - I believe stft of +- 3 is ok?
• LTFT does not move - pegged at -8.59% (yes, negative) - not sure why not moving, could be due to always clearing CEL and it never kicks in? I did unplug the MAF and plug back in, they went to 0% for a short while, then pegged back to the -8.59

1) Could the fuel regulator or pump in fact be failing, but just slowly?
2) Emissions Readiness Tests:

• Have not gotten the secondary air system readiness flag to green yet - get codes before enough cycles are done.
• Misfire, Fuel System, Components, Evaporative System, Oxygen Sensor tests all pass within a short drive.
• Had a harder time getting Catalyst, Oxygen Sensor Heater tests to pass- get the CEL by then, but do get them eventually.

3) Are there any other vacuum leak areas to check here?

Starting to worry that there is something catastrophically wrong with this car. Seems like lots of folks fix this with a few new hoses and CCV, but this is not the case here.

Any insight beyond what I have listed is greatly appreciated! Many thanks

[m3arod]

I'm going through the same exact thing right now with my e36 m3. I've replaced everything you have and still the same 2 codes come up and my trims are stuck at -8.1. I'm hoping we can both resolve this soon

[abcurran]

Sounds like fueling issues or dying/dead cats.

LTFT not moving seems suspect, but your analysis could be the reason. Constant clearing could keep the system from recognizing sufficient new data points to register a change to the trim, and the trims won't change until you've driven enough to acquire enough new data points.

Any mods to the car? What tune (if any)? What makes you certain these are negative LTFTs?

I battled 1188 & 1189, but I had positive LTFT numbers. Fixed air leak, (excess air passed MAF lead to O2 recognizing lean condition and adding fuel to compensate), but CEL stayed on. But, LTFT did drift downward back to zero, but not enough to be within acceptable CEL parameters. I changed tune, and problem was gone. Epic Motorsports tune was my issue.

If you're LTFT is registering a negative, your O2's are recognizing rich exhaust condition and ECU is pulling fuel.

Are your injectors leaking or spraying too much on each pulse? Cheapest starting point is to get them cleaned/tested, or swap them out with a known-good set.

Plugs are new, but are they gapped properly?

Dying cats might be letting too much un-burnt fuel reach the post cat O2 sensor. Are the cats original? The cats aren't really a known failure point on these cars, but anything is possible.

[jcasaccio]

The car only has 52k on it- it’s bone stock. Would be surprised if cats are bad already, no?

I’ll try injector cleaning . This would make sense- such low mileage = car sitting a lot and they could gum up.
.

[NolliM3]

You really need to use INPA or DIS to diagnose your car...anything else, and you would be wasting your time. Have an old laptop laying around...convert it into a dedicated diagnostic BMW tool!

[abcurran]

Originally Posted by jcasaccio

The car only has 52k on it- it’s bone stock. Would be surprised if cats are bad already, no?

I’ll try injector cleaning . This would make sense- such low mileage = car sitting a lot and they could gum up.

Remember that the car is 22 years old, after all.

At that mileage, yes, cats wouldn't seem the culprit. But, the low mileage indicates infrequent use, lots of short drives or a combination of both. Maybe short drives don't let the cats get a chance reach operating temps, and that's resulted in clogging/premature failure?

The GT1 diagnostic tool mentioned above should certainly help narrow this down. I don't have one and last I checked they're quite expensive, but maybe worth it for you?

[jayjaya29]

Post cats play no part in this problem. Get the injectors cleaned and report back.

[JPoland]

Originally Posted by jayjaya29

Post cats play no part in this problem. Get the injectors cleaned and report back.

Yes post cat O2s don't change the fuel trim. That is why you can plug in a simulator and it won't affect the car. It is just to monitor the operation of the cats.

[jcasaccio]

Ok, I’ll see if there’s any local enthusiasts in NW burbs of Chicago that know how to read INPA output- I do not. Maybe they would take a ride with me for a 12 pack or lunch...

I dumped a can of BG 44k fuel system cleaner in there for now and will run that through a tank of gas- maybe STFT will change. Then I think I’ll pull injectors and have sent for cleaning .

[m3arod]

I think I just figured out my issue with my e36 m3. I've been puzzled with the same issue and read to test and clean the injectors. Now that I'm really looking at the injectors they're the pink ones and it hit me! Aren't the pink injectors the 24lb injectors? If thats the case my dme is leaning out the mixture to compensate for the extra fuel going into the engine. PLEASE CORRECT ME IF I'M WRONG