Help me diagnose problems with the 318is

[royalflush313]

The symptoms start after the engine is fully warmed up. The car drives great when it is cold, but usually after about 30 minutes of driving, the symptoms start.

- slightly irratic idle (very slightly, moving from maybe 600-850 rpm range at the most)
- car is very shaky at idle (the whole car is shaky, including the shifter)
- when starting from 1st gear, the car hesitates, and though the car starts to move, it does not really take off for couple seconds.
- same problem with hesitation when shifting up, usually the symptoms are most apparent in lower RPM range.

- Engine light does NOT come on
- the car revs up fine when in neutral (clutch in, or shifter in neutral position), the hesitation is only when clutch is engaged / starting to be released.

- Car is stock, other than suspension and short shifter.

TIA!

[kowalski]

so its only under load that its doing this? does it seem like its got all its power? what year is it?

[KenC]

Fuel Pressure Regulator?

[royalflush313]

so its only under load that its doing this? does it seem like its got all its power? what year is it?

1991.
Hard to say about power-loss because the car stutters and does not accelerate smoothly.

It's only after the car is fully warmed up. Once the problem starts, all the symptoms (idle issue, shakiness, hesitation under acceleration) begin.

It's still drivable, but I would like to fix it asap.

[royalflush313]

Fuel Pressure Regulator?

I'll check into that. But if it's the fuel pressure regulator, it doesn't really make sense that the symptoms arise once the car is warmed up?

And also, the car revs up fine when it's in neutral, woudn't the symptom (hesitation, stuttering) be around when neutral too? I'm confused as to what would make the car hesitate so bad.

EDIT: Can i check if the FPR is functioning properly without replacing it?

[fabianyee]

how about the ICV????

I could be wrong, but it sounds like air leak. could be some air valve opened somewhere when it's warm...

[royalflush313]

how about the ICV????

I could be wrong, but it sounds like air leak. could be some air valve opened somewhere when it's warm...

The symptoms sound like a leak, but I really don't understand why it's only when the car is warm.

I don't think it's the ICV because if it was, the symptoms would likely to exist at all times.

Correct me if I'm wrong..

[BahnE30]

try disconnecting the o2 sensor, my car did something similar to that and turned out to be the o2 sensor. granted it was a 325 but same principle's apply.

[BavarianBimmer]

cracked airpiping ???

when warm they expand and the cracks dissapear

it sounds stupid :roll:

[royalflush313]

I hate how the problem is intermittent. It makes it that much harder to diagnose...

any other ideas?

Correct me if I'm wrong, but with all the problems you guys suggested, wouldn't the symptoms (hesitation) exist even when in neutral too?

[surebimmer]

I think your due to install two more cylinders and then you will have alot smother idle. But now trying to be more helpful, did you do anything lately to the car, tune up, etc. or did the problem just start? Try reseting the ECU to clear any adaptaions it may have stored.

[royalflush313]

I think your due to install two more cylinders and then you will have alot smother idle. But now trying to be more helpful, did you do anything lately to the car, tune up, etc. or did the problem just start? Try reseting the ECU to clear any adaptaions it may have stored.

nope, nothing.

Did an oil change in January, but other than, haven't touched a thing.
The problem is, I only drive about 500miles per month, so it's hard to say exactly when the problem started...

[royalflush313]

Update:

- The hose that connect to the throttle body was cracked, allowing more air in.
BavarianBimmer, looks like you were right on it.

- Spark plugs area was flooded with water, likely from when I wash the engine bay. Though I'm always careful, so it could be from when I left my hood up after washing the car, and started pouring - ya i know, very stupid of me.

EDIT:

Problems were fixed after replacing the above mentioned problems.