SOLVED!! I'm RICH baby! (OBDII s52 content)

[BlackSpeed66]

Ok here goes... trying to get this all into one thread. Hopefully i can get this solved soon!

Since I’ve been trying to get some miles on my car post-swap, it seems to be running quite rich. Monitoring the STFT on the OBDII app, which is still doing what it has been doing - hanging at +27.x% for several minutes, then moves to the opposite -27.x% for several minutes at a time. The O2 sensor voltage readings seem to mimic this movement as well, fluctuating from lean to rich and so on. The car will run fine when cold in open loop, but once closed loop kicks in, the same 4 codes show up. P1188, P1189, P0170 and P0173. It appears that the variances are significant enough that the LTFT refuses to even register. On more than one occasion, the ECU appears to have switched back into open loop due to the repeated faults.

I have smoke tested both the intake and crankcase twice and have not located any leaks. Also checked the brake booster to cover all my bases. As far as I can tell, the engine is sealed up as good as it can be. I’ve read about possible MAF issues, so I pulled the MAF and sprayed it down again with cleaner. I pulled back the rubber boot on the connector and with the car idling, was able to confirm it was getting battery power at the red/white and black wires. I also used my DMM to test the yellow & brown wires. At idle, it would read around .6 and when revved it would jump into the 1.x or sometimes 2.x volt range. Following this, I decided to chance a new MAF on eBay for $50.00. It seemed to cure a slight stumble off idle, but the same 4 codes above came back. The car is a hoot to drive and certainly pulls hard, but the gas mileage seems to be taking a visible hit due to it running rich. I haven’t quite taken it to redline yet since I’m still trying to break in the clutch.

Fuel pressure at idle (with vacuum line connected to the FPR on the rail) is approx. 43 psi. When revving the engine it does not seem to fluctuate much. I have an e39 OBDII fuel rail w/ the FPR built in. FPR itself is new Bosch.

With the vacuum line disconnected from the FPR, the fuel pressure is approximately 52 psi, which sounds in line with other info I’ve read.

With the car shut off and the fuel pressure gauge connected, it reads 46 psi immediately after shut off. I checked about 90 minutes later and it was showing 36 psi still. Injectors were refurbished by MEPEH on the site here. This leads me to believe fuel pressure is not an issue.

CCV system and hoses are all new (m50 manifold conversion). Oil separator is new OEM. With the oil cap off, it does have the slight vacuum as would be expected (will suck in a rubber glove about 1/2” to 3/4”). O2 sensors are new Bosch. Charging system is now in good order and runs a consistent 14V. Tune is thru Markert with the SAP, 3/2 valve and EWS flashed out. I am running the purge valve for the vapor canister. No real mods to the engine except for the m50 manifold and cold air intake.

Timing is really the only thing I haven’t looked at closely - does anyone know what the nominal readings might be?


My data is coming from the DashCommand app from Palmer Performance. I’ve got their ScanXL software on my other laptop and am currently trying to figure out how to view and work with some of the data logs I’ve attempted.

Thanks in advance for the help :drink:

[RainRider]

I'm obd1 s52 so don't know if this would help. I ran rich with a 80degree thermostat until I went to a 88 degree. That was the only factor.

[dunebuggyjay]

I'm obd1 s52 so don't know if this would help. I ran rich with a 80degree thermostat until I went to a 88 degree. That was the only factor.

how rich did you run? what afr? Ive been fighting a rich condition on my s52 swap, and have an 80 degree thermostat. After reading your poat, i just ordered an 88.

Jay

[RainRider]

I'd get black soot on the chrome ends of the exhaust within 500 miles of cleaning them. At times you could smell the hydrocarbons. Other than that no real diagnosis of how rich. I've put about 1300 miles since I changed the thermostat and no soot so far. Running a bosch 4 pin #0 280 217 502 1 747 155 afm.

[BlackSpeed66]

Yeah, that's how mine is right now. I'm cleaning the soot off the tail pipe every few days of driving.

I'm running the stock thermostat on my car. Finally took it out yesterday when ambient temps were 85º+ and the engine temp seemed to hold fine, so that's a plus.

I guess its possible the $50 eBay MAF could be questionable. I have no problem springing the $$$ for OEM but at that price, I want to make sure that's exactly what the issue is. I'm not sure what kind of luck people have with these cheaper aftermarket MAFs - or if I'd be better gambling with a used OEM MAF?

After a drive yesterday, I tried to keep track of where the timing is at. Seems at cruising, it ranges anywhere from 25º-30º or so. At idle, it's around 14º give or take. Not sure if that's the correct spec though.

[Sh3rpak!ng]

I'd say that's a place to start... I definitely would not trust any aftermarket ebay MAF. That's a very sensitive, precision electronic device that I doubt any aftermarket manufacturer can reliably reproduce. You can find used mafs in good shape for not much all the time. Check ebay, check classifieds.

Edit: you can always borrow a known good maf from a friend, plug it in and try it out before you buy one

[BlackSpeed66]

Yeah i was hoping to try the MAF from a friend-of-a-friend but he went and sold his e36 M3 haha. I have a "want to try" ad on the local forum. We'll see. I may just go and try for a used OEM MAF to satisfy my curiosity.

I can't figure out how to get some of these data logs from ScanXL off the computer (and it's slow and ancient), so i just took pics of the screen haha. This is from a cold-ish start to highway cruising at op-temp. Definitely some weirdness going on here.... could this be indicative of a (still) faulty MAF? Funny thing is, from the readings, it looks like the MAF is doing something?







You can see here the fuel trims and O2 voltages are flip-flopping lean to rich in the lower graph (lean is on the bottom and rich is on top)





I think this one above is where I did a 4th to 5th shift...

[328ijunkie]

lol. Your O2s are swapped. You have bank1 plugged into bank2 and vise versa.
;)

[BlackSpeed66]

OMG. Holy shit. Ok - I swear I marked and triple-checked this stuff when I put the engine in LOL. Hell I think I even tried to mark which connector went where.

I went out to the lot on my lunch and swapped the connections and went for a spin. Took a fresh data log which I'll try to post later. I'm now getting LTFT readings, which wasn't happening before. O2 voltage and STFT has (somewhat) leveled out. I didn't reset the ECU yet so I think it's trying to compensate from running so rich. I cleared any codes and so far nothing has come back yet.

So - one of two things happened. Either all my efforts were in vain and I still managed to mix up the connections, or the exhaust shop removed BOTH manifolds and mixed the sensors up on re-installation.

[agent]

Your O2s are swapped. You have bank1 plugged into bank2 and vise versa.
;)

Honest question: does it matter, and if so, why?

[328ijunkie]

Honest question: does it matter, and if so, why?

Bank1 needs to read bank1 and so on. If theyre switched ECU will trim extremely wacky as it basically tries to hover around ~14.7. It will bounce from 15.3-14.1 normally and it adds fuel to a bank, waits to see it then bounces back the other way assuming it sees the fuel add. If it doesnt see the fuel at the o2 (because its showing up on the other bank because the sensors are wrong) it keeps adding and adding till the trim maxes. The same applies to the other bank except in opposite form because its seeing all the fuel being added by the opposite bank so its constantly trying to pull fuel, which is a loop effect because that just pulls fuel from the real bank thats trying to add.

cliff notes: Fuel trims maxed lean on 1 bank and maxed rich on the other = sensors swapped.

[agent]

That's good info Dave, thanks.

[BlackSpeed66]

Alrighty - on the way home from work, everything seemed to be in check for the most part. The check engine light did come back on, but only with the P1188 and P1189 codes. The engine swap has about 1k miles on it over about 6 months with this rich condition - not sure if it's possible to foul the plugs and/or O2 sensors in that time. Thoughts?

Here are pics of the latest data logs from lunch time. Definitely a change LOL

[328ijunkie]

Now you're actually rich and ecu is pulling fuel. What injectors? What FPR? Vac line on fpr?

[BlackSpeed66]

Stock s52 injectors refurb'd by MEHPEH here on r3v. Stock Bosch FPR on the fuel rail (which i replaced during the swap). Vac line is connected - the pressure readings I pulled were in my first post.

I've parked the car for the next few days since it looks like the weather's gonna be crappy. I disconnected the battery so hopefully that will clear out the ECU from the "madness" it's been dealing with. Also going to replace the fuel filter since it's been about 30k miles. Hoping to take it for a spin over the weekend - will report back with what i find.