idle fluctuates

Hello,
I am sure this has been discussed before. Sorry to post without looking for previous discussions. My car has been Idling a little weird when first starting up but then fine after a few miles/minutes. At first I thought the computer just needed to re-learn since it has been inop for 2yrs. But now I am thinking sticky IACV.It idles about 1100 when first start up cold surging only minor amounts-not a problem. Most obvious when engine is warm-shut off for 10 minutes- re-start...that is when it surges the most and labors a bit to start. Surges from 500-1200 rpms. I replaced all hoses and sealed everything up real good when I put it all back together so I don't think I have an intake leak. Injectors are all fresh as well.
Thanks for any help.
Art

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Art Munson
Hello,
I am sure this has been discussed before. Sorry to post without looking for previous discussions. My car has been Idling a little weird when first starting up but then fine after a few miles/minutes. At first I thought the computer just needed to re-learn since it has been inop for 2yrs. But now I am thinking sticky IACV.It idles about 1100 when first start up cold surging only minor amounts-not a problem. Most obvious when engine is warm-shut off for 10 minutes- re-start...that is when it surges the most and labors a bit to start. Surges from 500-1200 rpms. I replaced all hoses and sealed everything up real good when I put it all back together so I don't think I have an intake leak. Injectors are all fresh as well.
Thanks for any help.
Art

Hey Art, what year and model do you have again?

Rick

Bad coolant temp sender. Sender thinks the car is warm when it's cold. After the car warms up, the data is now correct. When the car is cold, it should be running slightly rich. As it warms up, the mixture is leaned out.

alan

Thanks Alan,
How do I test the sensor? My car is a 1989 325ic auto. I guess they all have the m20 right?

Art, i am only making an assumption here. I believe the test is with a DVM (digital volt meter) set to Ohms. Pull off the connector, place the 2 meter probes on the 2 terminals and measure the Ohms. When cold you have one value, when the engine is warm, you have a second value. Not sure what the cold-hot values are, perhaps someone can help out?

alan

Thanks Alan,
I am now driving my '79 Fiat Spider until it sells then I will bring the BMW back out to drive it again, so it may be a while before I worry about the issue. I do have the good manual so I am sure it spells it out well. Once I am back to driving the car again I will certainly be posting more questions.....and I will learn to post more pictures.
Art

Sold the Fiat a couple weeks ago! So I am now driving my car daily. I figured out my "surging idle" problem. It was simply the stop screw on the throttle valve. It was holding the throttle valve open a bit too much, re-adjusted it and "all is well".
Hopefully I will have some time to start working on the car soon.

any pictures of where to find this screw? on the throttle body? any write-ups on surging idle? I am so tired of this persistent issue on my 87ic!

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alanrw
Art, i am only making an assumption here. I believe the test is with a DVM (digital volt meter) set to Ohms. Pull off the connector, place the 2 meter probes on the 2 terminals and measure the Ohms. When cold you have one value, when the engine is warm, you have a second value. Not sure what the cold-hot values are, perhaps someone can help out?

alan

Hi Al, the values are 3000 ohms when the engine is cold, and around 200 ohms when the engine is warm.

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When in doubt, use full throttle,
it may not improve the situation, but it will end the suspence.