hey guys, my e30 is having a really weird problem. from a cold start, the car idles fine, but after letting the car warm up to past the first line on the temp guage, the idle will sometimes spontaneously start going up to like 2500k and back down.. idk what this is, could it be air in the cooling lines? maybe its happening as the thermostat is opening? honestly idk what to look for im quite new to this.
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bmw its a m20 engine if i didnt specify -
Try unplugging the O2 sensor. Mine was doing the same thing. High idle at warm and stuttering/loss of power while warming up.
Could also be ICV or vacuum leaks.
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1987 325e Lachssilber w/ MarkD chip and late bumpers, Zender EVO spoiler, s3.25 LSD
Originally posted by nandoComment
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I think it maybe your temprature sensor that sends temp back to you computer it one of three that sit on the top of your thermostat.Comment
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I have the exact same issue, but I've replaced the ign components, cleaned afm, icv, intake mani, replaced o2 sensor, did a timing belt and assorted gaskets and seals. No vacuum leak that I was able to find.Last edited by wannasupra; 04-01-2015, 02:07 PM.Comment
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A high, surging idle means the engine is breathing through places it shouldn't be (ie downstream of the AFM so the ECU has no idea there's a problem). The cause is almost always vacuum leaks or a bad/dirty ICV. You said you cleaned your ICV, so don't throw parts at her just yet. How do you check for vacuum leaks? Praying and spraying with water/aerosol/carb cleaner is for dorks. Google will tell you how to make an awesome smoke tester on the cheap. Here's my gangster method that has never failed me.
Pull off the AFM. Grab a disposable rubber glove, stab a small hole in it, and shove in a piece of tubing large enough to blow into. Fit the glove over the rubber intake elbow to form an airtight seal. Shove rags or the equivalent into the tailpipes to seal the system. Prop the throttle wide open. Light up your favorite legal/illegal smokable and blow said smoke into the tubing. It will take a minute to fill your intake and motor with smoke, but as soon as you do, smoke will start to leak from your trouble spots and generally rise straight up. Fixing these leaks will result in much stabler running.Last edited by EatsHondas; 04-03-2015, 02:19 AM.1989 325i Lachssilber Sedan
5-Speed Swapped
M30B35 Swapped
MegaSquirt MS3X
1987 325i Lachssilber Sedan
260k OEM Automatic Daily Baby
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