RPM goes Up & Down when starting

[alone]

Posted this thread in other forum too, but just wanna see what type of suggestions and answers i would get here, hopefully it will narrow down my problem with my 95' 325i

When i start my car, the RPM would go up and down, as it woul REV up and down then it would die unless i keep giving it gas, but when i release the gas, it would do the same thing then DIE !!!

After serveral times of this, then eventually it will settle down and not die anymore, i guess as the engine heated up.

One of my friend said that I might have a vacuum leak somewhere, but cant be sure and don't know where yet. So any idea where it could be leaking and how do I detect a leaking vacuum ?

Others suggested that it might be the O2 sensor ?

Others said that the Fuel PUMP isn't giving it gas.
..................so what do u guys think ?

[wswilburn]

Many things can cause this symptom. Is the check engine light on? If so, can you read the codes? This will usually tell you about faulty O2 sensor, vacuum leak, etc. Another possibility, that usually won't trigger the CE light is a partially clogged injector.

[alone]

Nope, check engine light does NOT come on.

Weird thing is, it acts diffrently today, RMP goes up when started engine then it settles down, but when i give it gas, it goes up and down again.
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OK, I just wanna add that this problem started since i degreased and washed my engine which flooded 4 out of 6 spark plugs holes. YES, sorry, it was a dumb thing to do, but sorry again, i'm a new bimmer owner. I didn't know water can get to the spark plugs with the engine cover on.

That day, my car was running really weird, shaky and no power at all and smoke were coming out from back of the engine. Also, I had the car running on idle for 2 hours trying to dry up whatever might still be wet in the engine to no success, but later that same very day when i found out that water had flooded the spark plugs holes, I blew out all the water in the spark plugs hole and replaced all the spark plugs & oil changed.

So ever since then I'm having this problem. So what did i burned out ?

[wswilburn]

I should say first, I'm not an expert. I'm just going on my experiences with my M3 and other cars. Here is my opinion, FWIW.

Yea, when the spark plug holes were flooded, I could see there being a problem. You were probably getting arcing across the plugs. Drying everything out should fix it, I would think. Even if you left some residue on the plugs, you say they've been changed out anyway. I can't imagine you damaged anything permanently.

Another possibility is something is still wet. The ignition coils are the obvious things to check. I doubt this though for two reasons. First, they are sealed pretty well. Second, when I had a bad coil, causing intermittent missing,the CE light came on. If you think this is a possibility, you could take them out again and check for water, and set them out to dry for a while.

A third possibility is you didn't put something back properly after the plug replacement work. Going by memory, I don't think there is much to screw up. A couple of ground wires and the ignition coil connectors are all I remember.

A fourth possibility is it is unrelated to the engine washing. Either you notice now a pre-existing problem, or its just coincidence to be showing up now. Bentley has a troubleshooting guide on p. 100-15, but they say that most of the symptoms listed will cause the CE light to come on.

[JhwShark]

I do not know your model that well...but water can help clean out crud in hose connections that may have hidden degraded (cracked) hose ends...creating a vacuum issue. A mighty vac (small vac pump from auto parts store) connected, and applied, to a hose opening can tell you if you have a tight seal.

Other issues may be electrical...the leads to the plugs could be arching (still), the plug head the leads go to (if it has a piece that sits on the spark plug which the plug wires go to) could be degraded/shorting. You do not have a distributor, right?

You did not do anything to the fuel pump, it doesn't seem that direction; but fuel pressure regulator?? It probably isn't fuel delivery if it ran fine before you "hosed" it.
Jon

[alone]

Update:

The weird thing is that I did an oil change yesterday afternoon then drive it home, the problem was still there, but this morning when i started it up and drove it to work, the problem was gone. Also test drive it couple times and starting ups, the problem seem to be gone.

Let's wait and see how its gonna run tomorrow morning.

[wswilburn]

Sounds like whatever was wet has finally dried out. Good luck!

[alone]

update:

What I just realized today is that, maybe water also gotten into one or a few of the the intake manifolds, maybe that's why it was smoking the first day it happened.

With these few really hot couple days, I guess it finly dried up.
The car is now running smooth as ever.

Thanks!