# 318i rough idle at start



## kioneo (Jan 8, 2004)

I've got a small issue with my 1991 318i (E30, M42) that creaps up every now and then. Basically, from a cold start, the car will sometimes idle very roughly for about a minute or so (or less, if I give it some gas to help it along). The engine shakes and sort of sputters a bit. Once it clears up, it runs very well.

At first I thought it may be water or moisture buildup in the gas tank, but after washing it several times and after some heavy rains (with varying fuel tank fill levels) it doesn't seem to be water.

Even more puzzling, it can go months without having a problem. Even after not driving it at all on the weekend, it will likely start just fine on Monday.

I've searched around and not found much else discussed, other than one person who mentioned having a similar problem when he moved the car a small distance, let it sit, then started it up. I haven't done enough experimentation, but I think that I may have a similar situation. This Saturday, I moved it about 50 feet from the street to the driveway and let it sit there overnight. When I went to reposition it on the driveway on Sunday (to wash it) it gave me the trouble.

At this point I'm rather puzzled. Relating to idling, I have had the following items replaced (not in an attempt to cure this issue, but rather because of them failing):
- Vacuum hoses
- Idle control valve

Any suggestions on what might be causing this or where else to look?


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## SergioK (Aug 14, 2002)

I had an old 1980 MBZ that did exactly that. The engine (2.8l dohc) had 200,000+ miles on it though. Every morning, the engine would cough and spurt until it warmed up just a bit, then it would smooth out and run perfectly fine.

I figured it was the plugs and a symptom of its high mileage but there was nothing wrong, per se, with it.


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## Fast Bob (Jun 4, 2004)

On a car this old, I would`nt be surprised if the valve seals were the culprit here....when the car sits for a while, a little oil gets past the worn seals, and remains in the combustion chamber. Upon startup, the plugs are slightly fouled, but after a minute of running, everything heats up and burns the oil out of the CC, and the engine smooths out. This is more noticeable on a 4-cylinder engine, as the firing impulses are 90 degrees apart. Have you noticed a puff of smoke from the exhaust on cold start-up?

Regards,
Bob


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## kioneo (Jan 8, 2004)

Fast Bob said:


> Have you noticed a puff of smoke from the exhaust on cold start-up?


I haven't noticed any smoke from the exhaust, but then again I haven't been looking that closely. Also, my car is extremely friendly on oil. I change oil/filter every 5000 miles and haven't had to add any oil in between changes in the 30,000+ miles I've owned it (153,000 miles on the odo). I'll have a friend observe the exhaust when I try to reproduce the situation.

Are valve seals something that can be easily replaced? I'm looking at having my valve timing checked/adjusted shortly as a maintenance item (given the high mileage).


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## Fast Bob (Jun 4, 2004)

kioneo said:


> I haven't noticed any smoke from the exhaust, but then again I haven't been looking that closely. Also, my car is extremely friendly on oil. I change oil/filter every 5000 miles and haven't had to add any oil in between changes in the 30,000+ miles I've owned it (153,000 miles on the odo). I'll have a friend observe the exhaust when I try to reproduce the situation.
> 
> Are valve seals something that can be easily replaced? I'm looking at having my valve timing checked/adjusted shortly as a maintenance item (given the high mileage).


Given the age & mileage of the car, I would have a compression/leakdown test performed to determine if it needs anything beyond minor adjustments....this would be a logical starting point. Worn valve seals is more of a minor inconvenience than anything, i.e., the rough idle on cold start-up.... it really does`nt make the engine consume an appreciable amount of oil.

Regards,
Bob


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## ted (Aug 13, 2004)

kioneo said:


> I've got a small issue with my 1991 318i (E30, M42) that creaps up every now and then. Basically, from a cold start, the car will sometimes idle very roughly for about a minute or so (or less, if I give it some gas to help it along). The engine shakes and sort of sputters a bit. Once it clears up, it runs very well.
> 
> At first I thought it may be water or moisture buildup in the gas tank, but after washing it several times and after some heavy rains (with varying fuel tank fill levels) it doesn't seem to be water.
> 
> ...


Hi,

I'm having the same problem with my 1995 318is. I get a Fault Code of 1286
which means Knock Control Test Pulse not detected by ECU.

I haven't had time to investigate further.

Ted


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