RPM not steady

[joe98020]

I have another post titled transmission hunting. Well now I think it is the motor. While idling in park at 1500rpm it will jump to 2000 and then drop to 1000 and eventually return to 1500. While driving it will jump 200 to 300 while driving. 2003 4.4 with 97k on it. Any ideas?

[bastereo]

That idle is way too high. Should be more like 700 rpm.
You are right that is problem.

[joe98020]

I probably wasn't clear. When I manually increase the rpm. The normal idle is not that high.

[BavariaTexan]

manually increase? you mean push the gas pedal?

[joe98020]

Yes when I press on the gas to bring the rpm's to 1500. I originally thought the "hunting" problem was the transmission. I would not consider myself mechanically inclined but would like to have some idea about what is going wrong prior to taking it into the shop. Thanks again for everyones help. The post on FSR was excellent and saved me money. Realizing that I will probably never be able to post an answer to someone's question; the only way I can contribute is to thank the rest of you.

[HPIA4v2]

Hard to say, but I'll start with the usual suspects:
- plugs
- air filter
- trace any air leaks on intake
- clean MAF (use the CRC aerosol it works for me, the fainte vibration during pick up is gone)
- replace 3/8' vacuum hoses (item 10, 12, and 15) they are brittle and leak for > 6yr old vehicle. I garaged my car and when I work on Valley-pan I found them to be goner.

good luck.

[J.Belknap]

While you're at it, inspect the throttle body boot, Oil separator (and it's lines), dipstick, oil cap, clean off O2 sensors, cam sensors. Easy to get carried away, eh? But, the system works as a system and all of it wears...

[nezarnuaimat]

There can be many many reasons. However, the rpm fluctuation can be easily discovered by computer diagnosis test.

[JCL]

Originally Posted by joe98020

Yes when I press on the gas to bring the rpm's to 1500. I originally thought the "hunting" problem was the transmission. I would not consider myself mechanically inclined but would like to have some idea about what is going wrong prior to taking it into the shop.

I fully understand where you are coming from. It would be nice to know the problem in advance. The problem is, that is a totally unrealistic expectation.

There are two classifications of individuals on here and other boards, those who fix it themselves and those who take it to a shop. Of the first group, a subset are sometimes able to diagnose the correct problem from the symptoms, and the rest tend to replace components to see if they hit the right one (shotgun approach). Of the latter group, many like working on their vehicles and after replacing multiple components feel good about having completed the work, whether or not it was an efficient way to resolve the original problem.

If you aren't going to fix it yourself, you actually shouldn't take your own diagnosis to your mechanic. It will usually cost you more. I've been on both sides of that equation, as a customer and in the shop and as a service manager (not at a BMW dealer).

Trying to diagnose it yourself is an acknowledgement that you don't trust the repair facility. That is the real issue. Spend your effort determining which shop to take it to, check references, and establish a relationship with them. Your job as a customer is to fully document and describe the symptoms so that the trained diagnostician can zero in on the actual problem. You need to hold them accountable, and describe your expectations (ie quote before repair), but it is not your role to provide a list of possible causes. It was always painful when customers came in with that sort of a list. We would listen patiently, and often advise that we could replace all those things, but it would actually be cheaper if they let us figure out what was wrong first. Some customers just didn't like hearing that speech.

There are some good people on this board, but diagnosing over the internet is fraught with risk. When someone says "I had the same problem, it is xxxx" what they often mean is that they had similar symptoms, and in that case it was xxxx. Don't fall into the trap.

By all means educate yourself. Education is good. But the best education is around the symptoms, and being able to describe them succintly and accurately, and not around postulating potential causes for them. Just my $0.02.

[bcredliner]

I do a good share of my own work but a problem like this I would look for something obvious--you can see it or hear it from the suggested provided here--if nothing jumps out and bites you, I would suggest taking it to a dealer or highly recommended shop that works on BMWs and has diagnostic equipment to read the engine fault codes it is likely displaying. Very likely will solve the problem much sooner and with less cost.