Cold running issue

[CarsSuck]

So when its cold out, my car misses badly, especially under load but basically all the time. Once warmed up it gets better but will still miss, say driving up a grade on the highway.

I think i may have a leaky intake boot, it is cracked, but they seem superficial and not all the way through. It'll be replaced soon. Thats the only possibility of a vacuum leak. The CLT has been replaced along with cap, rotor plugs and O2 sensor.

If that doesnt fix it, what else could it be? Im thinking the intake temp sensor in the AFM. Does that mean i have to replace the whole unit?

[E30_fiend]

I'd say it can be narrowed down to the O2 sensor or the AFM.

I was having some of the same problems and it was my O2 sensor.







Taylor

[CarsSuck]

So is the AFM a dealer only part? Anyone know a good buy? I'm not gonna fuss around with used parts on this.

[SpecM]

So is the AFM a dealer only part? Anyone know a good buy? I'm not gonna fuss around with used parts on this.

you might want to on this one, they're esay to swap and cheap to pick up ($10-30)

NEW at dealer: over $600

REMAN aftermarket $200-400

[jlevie]

There are a number of possible causes that you haven't yet eliminated. So I'd say that a new AFM is premature. In order of probability I'd:

1) Replace each an every hose that connects to the intake as well as the dipstick o-rings and oil filler cap. And check for leaks at the intake manifold and injectors with carb cleaner.

2) Adjust the valves

3) Replace the ignition wires

4) Run the fuel pressure and delivery tests (documented in the Bentley manual)

5) Verify operation of the coolant temp sensor that provides data to the DME

If those don't eliminate the misfires I'd pull the injectors and sent them out to be cleaned and tested. Only after all other possibilities are exhausted would i consider swapping in a new AFM, DME, etc.

[CarsSuck]

Time to bump this thread.

I've replaced the fuel filter, fuel pump, and FPR. The pressure was a little lower than spec but this didnt fix my problem. New Coolant Temp sensor as well.

Coil, plugs, cap/rotor, and wires were all replaced at the beginning of this nightmare. Valves were adjusted not too long ago, but the problem is too inconsistent to be purely mechanical.

Vacuum was checked and was "steady" at idle and rose under throttle. Is there a spec for this? i couldn't find anything in the bently.

I drove the car monday (60s and sunny), it ran well, only missed once after start up. Drove the car Tuesday (low 40s rainy), it ran pretty well. I was driving up a steep hill in 3rd when it began to miss, crested the hill, popped it into neutral and rolled to a stop light, check engine light came on, but goes off when i blip the throttle or pull away. The code isn't being stored either, nothing from stomp test or peak code reader.

Last night i get into the car and start it (mid 30s rainy) missing badly right from start up. I didn't drive it. When it would miss the Econometer needle would bounce from zero to the center. I've also noticed that the lights in the HU and OBC dim when i step on the brake pedal or put the car into reverse. I've checked and cleaned a most of the grounds. Regular voltage test on the battery was good.

I'm pretty lost now. Where else should I look? I'll check the innards of the AFM and trace the CPS wires and check for cracks, but what else should I be looking for?

[jlevie]

Last night i get into the car and start it (mid 30s rainy) missing badly right from start up. I didn't drive it. When it would miss the Econometer needle would bounce from zero to the center.

That tends to suggest a fuel delivery problem. The Econometer is driven by the injector on time and having it jump to a high value tends to suggest that the DME is going to a wide injector pulse in an attempt to keep the engine running.

If this is a late model E30, you might be seeing the result of corrosion in the C191 connector. Otherwise I'd be suspicious of the fuel supply to the injector rail.

[CarsSuck]

The kick in the pants is that is the car runs like a top 98% of the time.

I guess ill just start checking all the wiring and connections in nasty, grimy detail.

I'm ready to take it to a shop, but I doubt they'll find it without hours and hours of time to diagnose. And even then, there's no guarantees.

I'll add that I have the MarkD 93 octane/19lb injector setup. Otherwise stock. One of the POs had an aftermarket alarm installed, then another owner had it disabled. The wiring is pretty wack under the dash already.

Thank You Mr. Levie.

[supernaughtIX]

engine grounding?

[abepark]

clean the plug under the intake manifold sometimes that gets come coolant drips and corrodes

[CarsSuck]

I believe it is the CPS. Only getting 470 ohms, and the connector had some coolant/corrosion on the sensor side. The part in on order and ill update this when i get it installed.

[CarsSuck]

'twas the CPS

20* and shes as smooth as ever.

I'll be more systematic in my diagnostics in the future. All it would have taken was 5 minutes with a multi meter.

Luckily, all the crap i replaced was old anyway, and some things like the coolant sensor didn't test right either.