Car running very lean...

[Kilomph]

I did an auto-manual swap on my 88 325iS, didn't touch a thing inside the engine bay (besides the usual 02 sensor and clutch line, etc). I'm now getting ~35 MPG with a rough idle and am down on power. She ran beautifully before the swap, would spin to redline without a hitch. The idle doesn't bounce around (no signs of vacuum leaks), and I'm pretty sure it's not running on 5 cylinders. What are the chances of a catalytic converter blocking the exhaust path? I've done plenty of E36 swaps, and banged around a bunch of cats without a problem.

Would a clogged cat cause a lean or rich running engine?

Thanks

[h82crash]

Probably, but a faulty O2 sensor will. Throw a code reader on there, should tell ya.

[84E30]

u know what i'm havin the same problem... how do u do the code reader?
my shits runnin lean too... wen i'm rollin down my hill early in the morning
car is cold it starts poppin from my exhaust...

[Kilomph]

http://www.unofficialbmw.com/repair_faqs/motronic.html

I'm just going to order a cat from bav auto ($410 + shipping) and a new o2 sensor. I'll troubleshoot after that. My NOx levels were really high, about 1000 over the legal limit.

[bsop]

if your car is over 15 years old, emissions dont matter

[lifeiskaos]

if your car is over 15 years old, emissions dont matter

its not like that in all states

[Kilomph]

Swapped in the new cat, along with a new o2, spark plugs, and an air filter. The OEM muffler is trashed, I was able to shake huge chunks of rusted metal out of it, and after startup it was spitting bits of rust for a couple of minutes. The car seems to be running better, I haven't driven it very far yet though.

The drone from the muffler is exhausting, I'm considering the Scorpion muffler from BavAuto, I want something louder then OEM/IE3s muffler. Any suggestions? How's the fitment on the Scorpion now? I read that it used to be off, designed more for Euro E30s, but that they recently re-designed it for US E30s.

[Kilomph]

Finally got around to an inspection.

New:

Air Filter
Fuel Filter
Spark Plugs
Catalytic converter
Muffler
o2
Oil
Intake Boot

Failed for NOx

Standard is 1323, I got 2275.

Passed for HC

Standard 173, I got 142.

CO%

Standard .98 I got .53

CO2% read 14.1

O2% read .05

I guess I might have a slight vacuum leak? The idle is usually solid, sometimes on cold mornings it might hop around 50-100 RPM. Any other ideas? I'll check the plugs soon to make sure all cylinders are firing properly. I'm so effing annoyed. My car has been running a bit hot, it creeps a bit past the 12 'oclock point if I let it sit for too long, and once it's been sitting for a while it won't blow hot air, only when I start moving again will it heat back up.

[Knockenwelle]

Sounds like it's still lean. The really low O2 and high NOx indicate a lean, hot burn. Keep looking...

Does anyone know what it takes to reset the Motronic 1.0? Do you just disconnect the battery for a while like for the 1.3?

[E30_fiend]

A very common problem with E30s and smogs is that the smog techs don't let the cat get hot enough to fire up and burn off the emissions going through it. If you have a free retest, before you start it sit in the car with your foot on the gas at about 3k to get the exhaust really hot. You want the exhaust as hot as you can get it before you drive onto the rollers.

And yeah you can reset the computer if you disconnect both wires from the battery and touch them together to get every last ounce of voltage out of there. Leave it for a little while and then reconnect it.







Taylor

[jlevie]

My car has been running a bit hot, it creeps a bit past the 12 'oclock point if I let it sit for too long, and once it's been sitting for a while it won't blow hot air, only when I start moving again will it heat back up

That is almost certainly air in the cooling system from an improper bleed or a leaking head gasket.

The most likely suspects (with a fresh O2 sensor in place) for a lean condition would be intake leaks, a bad AFM, or low fuel pressure. The fuel pressure and delivery checks are in the Bentley manual and a procedure for checking the AFM is at http://frwilk.com/944dme/afm.htm

[indecline]

Did you Swap the ECU to a Manuel one? If your using the same one that was with the auto trans it is not fully compatible with a Manuel swap. The idle is set higher on a 5-speed.

[jlevie]

Did you Swap the ECU to a Manuel one? If your using the same one that was with the auto trans it is not fully compatible with a Manuel swap. The idle is set higher on a 5-speed.

The ECU uses on a manual car is exactly the same as that used on an auto.

[indecline]

Well Don't Manuel cars tend to have a higher idle? I know Autos idle @ 700rpms and Manuels are close to 1K right???

[Knockenwelle]

^^^ Hey, back then, she was just paying for college. Now, she is (was) soliciting votes. Still an *honest* pursuit, and still not bad lookin'

No, the idle speed spec is the same. There is a connector above the glovebox (next to the computer) that accepts a jumper which tells the Motronic which trans the car has. I don't remember which way is which, but the computer will slightly richen the mixture for the manual trans. Also, the gearshift switches for the auto tell the computer when the trans is in gear, and to therefore compensate the idle accordingly. Manual trans just doesn't have that function.