Need help with my 87 325is...

[naissur_mk2]

Hey everybody, i am new to this forum, and really need an advice:
I started my car earlier today and it started reving the engine by itself . It goes from 1000rpms to 2000, and back and forth, back and forth... does anyone have any idea what could be wrong with it? i would appriciate any help and suggestions,

Thanks a lot.

 

[Chesty Bonds]

G'day mate,
I'm not exactly sure what the self-revving might emanate from but i wouldn't rule out the possibility of having a dodgy ECU on your engine. This could be interrupting the air and fuel mixture into the engine. It couldn't be the throttle itself because it would either stick open or closed. Perhaps someone else is able to give you a more definitive answer... Good luck

 

[epj3]

It's something to do with the idle system. Do you have any check engine lights? That's the unfortunate thing - especially with these cars -- the electronic fuel injection/engine management system is VERY complex. There are so many things that could go wrong.

If the revving stops after a while, it's probably the idle control valve, the cold start injector (Though I've read that only the "E" engines had those????), or, unfortunately, the idle control system.

If it does it all the time, you might need a new ecu.

 

[equate]

Clean out the icv, see if that fixes it. Takes about 35 seconds to get it off the engine

 

[naissur_mk2]

Hey guys, i really appriciate all of your information.

Well, this afternoon i drove my car an my check engine light went on. My car also did this to me before 2 times. Once it happened when i was driving on a highway and it stopped after 30 min down the road. The second time it happened when i started the car, but it went away when i let the car sit for like 2 hours.
This time, "She" was sitting outside overnight and it still does it this morning... . So i guess i am gonna grab my Bently manual , and that's gonna be my game plan for the Sunday.

If you guys will have any other suggestions, please let me know,

Thanks a lot

 

[hyperollah]

that problem is the ecu for sure. the ecu is bad. you need to go to a junk yard to pick one up or get a new one that matches your ecu. its under the dash. take out the glove and the plastic cover and the bosvh ecu box should be right there. the number on the box is the number ecu you need to replace.

 

[epj3]

that problem is the ecu for sure. the ecu is bad. you need to go to a junk yard to pick one up or get a new one that matches your ecu. its under the dash. take out the glove and the plastic cover and the bosvh ecu box should be right there. the number on the box is the number ecu you need to replace.

Um, I doubt it. Sounds like a faulty oxygen sensor. Do you have much experience with the EFI system? The ECU is rarely the problem. If it were, it wouldn't be running at all at some point and time.

naissur_mk2 -- Next time the check engine light comes on... pull over, turn off the engine, then turn it to run (without starting the engine). Count how many times the check engine light blinks. 2 times means it is a faulty oxygen sensor. I am not sure what the others (1 blink, 3 blinks, or 4 blinks) are (I know that they are for the crank pos. sensor, airflow sensor, and something else..... BUT i don't remember which number does what.)

If it IS an oxygen sensor, get out your solder iron and a lot of electrical tape. Buy a "13725" oxygen sensor, and splice the wires. Just try to match them up the same as the old sensor (This is important, you could potentially ruin your new sensor.)

4-wire sensor with BMW connector - $140
4-wire sensor with chrysler connection requiring splicing - $40

Note, it is the EXACT same thing -- both the wire numbers AND the sensor itself is 100% identical. I've been driving with mine for about 8,000 miles and so has Mike (Mrferg).

 

[bichmgnt]

Could be a vacuum leak. Check the big boot between the AFM and the intake. Often there are splits along the folds that let air in that does not get measured by the AFM. This causes the idle to rev very similar to what you are seeing. The Check Engine light will also come on since the system is running very lean.

Good luck.

Steve

 

[naissur_mk2]

Alright, finally got some time to write with my stupid job... Well, i checked for vacuum leaks and everything looked fine. i took off the Idle control Valve, tried to clean it the best i could and it didn't help either.
One thing i thought was reaaly strange. When i took of the harness of the ICV, the car just kept on idling in exact the same way as it does when the harness is on. I wonder if that the ECU for sure, since the harness connects to the ICV to exchange the information? Also my "check engine" light hasn't came back on since it appered and disapeared two days ago. I kind of wish it did, so i could see how many times it would blink to see what the problem could be(Cuz it did start to blink last time it went on, i just didn't know what it was and just didn't pay attention to it . It went off when i disconnected my ECU).

Hey, EQUATE, i saw in some thread that you are from MN as well, do you know any BMW tuning shops i could take my car to with this problem or for any other future work...

Thanks a lot guys,

Cheers

 

[bichmgnt]

There's one more thing you can try. The fact that pulling the plug off the ICV didn't change anything made me think of it. At one point I had the same problem with revving that you have. Pulling that plug never changed the symptoms. It would occasionally go away for a bit but always came back. Found out it was a wiring issue.

Check the voltage on the plug to the ICV. If you have no voltage anywhere you prpbably have a broken wire or a bad Idle Control Computer. On my car there was a broken wire in the plug to the ICC. I had to take the ICC out and do some soldering but that fixed it and I've never had the problem again.

Good luck.

Steve

 

[epj3]

There's one more thing you can try. The fact that pulling the plug off the ICV didn't change anything made me think of it. At one point I had the same problem with revving that you have. Pulling that plug never changed the symptoms. It would occasionally go away for a bit but always came back. Found out it was a wiring issue.

Check the voltage on the plug to the ICV. If you have no voltage anywhere you prpbably have a broken wire or a bad Idle Control Computer. On my car there was a broken wire in the plug to the ICC. I had to take the ICC out and do some soldering but that fixed it and I've never had the problem again.

Good luck.

Steve

That does sound right. How much would an idle computer cost me? My car does the same thing...and it'd be nice to have it not surge in the mornings during the winter.