Weird idle. - BMW Forum

STROKETECHINTRAINING · 12-19-2006, 09:31 PM

On my '90 325i I have just done a tune up. Plugs, wires, rotor butten, dist cap. I do that on everything I buy used just because you dont know when it was done last. I have noticed a weird idle out of it. It kind of surges at idle and it does it bad enough to make the headlights pulse with the surge. I checked the alternator and batt and everything seems to be ok. Any insight on my problem?

Thanks, Jon

yammahamma · 12-20-2006, 10:35 AM

isn't there something where the engine or computer or something has to "learn" your driving style?

I know in my car whenever I have to un-hook the battery, the first 10-20 miles after hooking the battery back up there's a weird idle.....I've always thought that's the car re-learning my driving style....

After driving a few miles on a warmed up engine...it idles fine...

I might be wrong...and if I am somebody please correct me...

BMWJNKY · 12-20-2006, 10:44 AM

Valves could be adjusted too tight. What gap did you use on the plugs? If you use the small out of the box gap it can cause idle issues. At the shop I work at we use a .032-.034 gap on the M20 and M10 plugs.

STROKETECHINTRAINING · 12-20-2006, 11:51 AM

I dont recall off hand but I know i gapped the plugs according to Bentlys. I'll check the valve clearance and get back to you.

german-speed-demon · 12-20-2006, 05:07 PM

could also be the ICV

Starmavin · 12-20-2006, 06:10 PM

Test the coolant temp sensor.

german-speed-demon · 12-20-2006, 08:18 PM

Starmavin, when i buy my next e30, you better believe you're gonna be on my speed-PM list.

Bear · 12-20-2006, 09:11 PM

check the electrcial connector on the Idle Control valve, make sure it is on tight.

Starmavin · 12-20-2006, 10:20 PM

Over time, I have found that a bad or out of range coolant temp sensor causes the majority of bad idle/performance problems, the only other item that has a direct effect to the idle but can also leave highway driving performance alone is the throttle position switch. However, the symptoms must be described in full detail in order to find the cause.

JoeMadoo · 12-23-2006, 05:35 PM

You could just unplug the coolant temp switch, it will idle at 800 or so but that will rule it out. I actually dont use it, i like the higher idle.

Starmavin · 12-24-2006, 06:12 PM

His car is a '90 so he won't have the temp switch.

www.e30Parts.com · 01-21-2007, 11:10 PM

Did anyone suggest to check the intake boot for cracks? Or to remove the idle control valve and give it a good cleaning? Or - check and listen for vacuum leaks? All of which WILL effect the IDLE of the car.

Rfitz25 · 01-22-2007, 05:33 PM

On mine it was the TPS. (hard to get too)
(Star Mavin called it right too)
A new AFM helped too. $$$
Not sure if the new temp sensor helped but it was cheap.
Make sure you have all the little metal spring clips for the plastic connectors too, I had to get some from the bone yard for the temp sensor and the AFM connectors, now they dont fall off. LOL
Clean em all with electrical parts cleaner too.

Also, once around the block and my 173 ECU learned enough to handle my new Dinan chip. sweeeeet
(Which I still have 10 copies of, LOL)