erratic idle

[jw 325ic]

my fiances 91 325i has always had this weird problem. it goes from about 600 rpm to 900 rpms, but about the half of the time, it idles right. so thats what canceled the ICV out to me. my guess would be injectors, spark plugs, alternator/belt, valve adjustment or maybe even timing belt? like i said about half the time it will idle normally, but until the engine is perfectly at the half way mark on the temp gauge it idles funky. let me know what you guys think. thanks.

[rcko]

coolant temp ref sensor... diagnose what you can with mr. voltmeter... clean the icv and air flow meter...

[brandondan1]

My 87 used to surge like that when it was running lean. AFM usually makes a big difference. Blue coolant temp sensor good? I have a good condition ICV that you can try as well.

[jw 325ic]

My 87 used to surge like that when it was running lean. AFM usually makes a big difference. Blue coolant temp sensor good? I have a good condition ICV that you can try as well.

hmm, i know her coolant light used to come on every now and then, but the level never changed. it doesnt leak at all or run hot, stay perfectly in the center of the gauge. but it hasnt done that in awhile. wheres that coolant temp sensor located? ill clean up the icv for now, and see if that helps to try and save us some gas.

[jlevie]

Intake leak, sticky ICV, or bad engine temperature input to the DME are the most likely causes. The ICV may not be dirty enough to affect operation once the engine is hot, but when the engine and ICV are cold oil in the ICV will be more viscous and may cause problems.

[Toms73NovaSS]

Also, the gage on the dash has is own separate sender for the temp and the DME has its own. The gage has no impact on the computer functioning.

[brandondan1]

You can see the temp sensors on the thermostat housing if you look from the passenger side. The brown one is for the cluster gauge, while the blue one is for the fuel injection. The last one I had was corroded as hell, so u might want to unscrew it and check, as well as measure the resistance if it looks fine.

Might wanna clean the ICV just in case, as well as check if your intake boots have any cracks. The small vacuum hose from the FPR to the manifold could be deteriorated. The breather hose at the top left corner of the valve cover could also have some cloggage, or be defective.

[rmousir]

Might wanna clean the ICV just in case,

What is that and how do I check it?

Thanks.

[jw 325ic]

Might wanna clean the ICV just in case,

What is that and how do I check it?

Thanks.

thanks brandon ill get on that this weekend. the ICV is the Idle Control Valve. looks like this:

[rmousir]

thanks very much for the picture. where is it located?

[bwanac]

coolant temp ref sensor... diagnose what you can with mr. voltmeter...

ditto. had the same problem.. seemed to fix it up after nothing else did.

[jw 325ic]

thanks very much for the picture. where is it located?

look near the intake manifold. i think on the 325i's its on the drivers side of the manifold and on etas its on the passenger.

[brandondan1]

Might wanna clean the ICV just in case,

What is that and how do I check it?

Thanks.

Yours is probably L-shaped, since its an 87. It's connected at the main intake boot(by the AFM) and the throttle body housing. You might need to disconnect some clamps to get wiggle room so you can pull it out. Then spray some carb cleaner inside and jiggle the mechanism so it moves freely.

[Scott314]

How can you tell if your ICV is good or bad? I cleaned mine, and it buzzes when the key is on, but I did the check recommended in the Bentley, where you get the engine to operating temperature, shut it off, and then turn the key back to the on position. The ICV is supposed to open half way. Mine stayed shut, and if I disconnected it, opened it by hand, and then plugged it back in, it snapped all the way shut again. Does this mean its bad?