M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: cjshelley on January 13, 2011, 07:52:39 PM
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Okay, I know there are a few threads out there about this issue and a solution remains elusive. Here are my symptoms on my 1991 318i with 230k:
1) hard cold start, sometimes have to give it gas for 20-30 seconds before it will idle
2) inconsistent power delivery when cold. if I give it too much gas, the thing loses power, jerks, surges, loses power again, etc. if I let up off the gas, it evens out. This happens for the first few minutes of driving unless I let it warm up before hand
3) after driving up to temp, it sometimes (usually) is difficult to start after being shut off. if it does start, it is quite rough and sometimes requires some more juice from the gas pedal. it lugs and barely idles for a few secs and then surges way up because I'm pressing on the gas to keep it running. Sometimes a belt squeals when this happens - that one's a complete mystery to me for now.
4) even after it's warmed up it can lose power under load (i.e. making it difficult to accelerate to freeway speeds). I'll start accelerating just fine and then the power just cuts and sometimes jerks, but not as badly as it does during a cold start. Occasionally my CEL comes on when I'm on the freeway (the power loss happens at cruising speed if I, say, start going up a gentle freeway incline).
That should cover the symptoms, now for what I've done to trouble shoot.
1) the first thing I did was clean "the mess under the intake" thinking it was a vacuum issue. I replaced the O2 sensor at the same time. No change.
2) double checked my ICV. It's clean and it works.
3) checked my mass airflow meter. it tested bad, but didn't throw a CEL code. apparently the car has a default fuel map that it reverts to if the mass sensor fails so it will still drive okay. I tested 3 different junkyard meters before I found one that tested "good." the car ran WORSE - it also triggered a CEL code for my mass meter. I put the old one back on and the car became drivable again, albeit with the same symptoms. No CEL code anymore.
4) drained the tank, checked for crud on the fuel pump. changed fuel filter. currently on my 3rd bottle of fuel system cleaner. It SEEMED to improve with the fuel system cleaner at first, but the symptoms returned.
5) encouraged by the results from the fuel system cleaner, I took my injectors out and cleaned them, as well as put new seals on them (I thought perhaps one of my seals was busted and intermittently let pressure out the top, thus losing compression in one cylinder). The first two times I drove it was almost flawless. it started right up when cold and there was no driving stutter... my symptoms returned today and I almost got stranded at the parts store getting another bottle of Seafoam.
TPS is good, Temp sensor... I don't know, but it doesn't throw a code. I think my pressure regulator is fine, but I haven't checked my fuel pressure. it doesn't make sense for it to be temperature related and my vacuum lines are all replaced. Furthermore, lots of these things have already been suggested in some of the other threads that describe similar issues with no tangible result. Another suggestion was a plug on the wiring harness having to do with the catalytic converter and that checks out, too. There have been brief mentions of the cam sensor (maybe that would have to do with my sqealing belt on a warm start?) and also a clogged evap canister. I checked my engine ground and, while the insulation is screwed and it's dirty, everything's intact and nothing is frayed. my entire intake looks pretty clean. Other people in other threads have replaced the ECU with no change, as well.
My final note is that before I cleaned my injectors (which looked good, anyway) my CEL threw a "running lean" code. This has since ceased. Even though my CEL comes on while driving, the stomp test doesn't give an error. This makes me lean away from some people saying that injectors are dumping too much fuel in on start. the only difference in performance that I've been able to measure has to do with the cleanliness of the fuel system, but everything seems just fine! Okay, I believe that's my definitive analysis of my issue. someone. please. for the love of god. solve it?
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I should also add that my spark plugs look fine and my brake booster vacuum is fine.... I'll keep adding things I forget as I remember.