Warm up issues

[Laernu]

I'm having warm up issues with my 85 318i. When I do a cold start my car will idle poorly and if I try and drive it pretty much has no power at all but once you get it to like 3000rpm it'll move. If I let I idle for a little bit eventually it'll fix it self out and drive normally. If I make a quick stop and come back to the car 30mins later after being warmed up the car will idle like crap again and take a lot longer to fix it's self out.

Now I've pin pointed what's causing this which is the coolant temp sensor that sends the signal to the temp gauge. During the idling issue the temp gauge would read funny like the car blows hot air but the temp gauge isn't really reading. I'm confused cause I thought this sensor had nothing to do with how the car would run, I thought it was just for the temp gauge but when I unplug it while it's idling like crap the car runs fine but idles high..

I cannot find anything in the Bentley manual about this sensor.. I don't just wanna buy another sensor without trying to test it to make sure it's not some kind of wiring issue.

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[loki_]

There are two water temp sensors on the top front of the engine. The one you need is like $30 for a bosch one or $4 for a generic one from rockauto. There is a test for the sensor by testing the resistance at various temperatures, but the sensor is cheap enough so it might not be worth the headache. The only other thing that jumps out at me from your description would possibly be a defective IAC valve. If the valve is stuck then it could cause rough running at one temp and smooth at another. I'd pop in a new water temp sensor and see if that resolves the issue and go from there.

[Laernu]

The temp sensor I'm talking about is the one that goes to the cluster. Which j thought played no part in running operation. I replaced the iac like a year ago with one from vdo. I'll test it to make sure it's opening and closing .

Thanks for the reply

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