Engine idle. Once again now that I have the car to look at.

[Guest yTTyTee]

I am having a problem with the idle. Its kinda complicated so I'll first start with the symptoms. First I start up the car from cold. It runs fine until the engine begies to heat up, the idle begins to drop(like it should) but as soon as it gets to about 1000 rpms it sputters and dies.

 

What I did to diagnose:

I disconected the water temperature sensor, since this is what causes the idle to be high when the car is cold, and normal when the car is at a good temperature. I started up the car, it sputtered and died almost right away becuase the idle wasn't high enough for how cold the engine was. I turned up the idle speed screw to about 1500 RPMs and restarted the car, it started up beautifully this time. I ran it for a little bit to get it warm, then I reconected the water temp sensor, the idle went up about 200 rpms then began to drop gradually until is sputtered and died again around 1000 rpms. The next time I did the same thing but right before it sputtered and died I disconected the water sensor quickly, the idle speed went up instantly and keeped the car running. I can repeat this many times, even after the car has warmed up enough so that the sensor should't have any resistance to cause high idle.

I still couldn't get the idle below 1500 RPMs or it would die. So I decided to try and disconect the Thermotime switch and see if that made any difference. With this off I believe the cold start valve operates for the normal time limit when starting the car, no matter the temperature. For some reason with this off, I could drop the idle to 1000, but no less (800 I believe is the correct idle speed). When I cold start the car, I just have to rev it a bit, and it will stay running. The car runs beautifully with both of these sensors off, however I'm still not at the optimal 800 rpm idle speed, and it is the summer so the car isn't very cold when I start it up. I also tried replacing the water temp sensor with one from Shmucks, this one http://www.partsamerica.com/PartDetails.asp?SourceArea=&SourcePage=SEARCHRESULTS&MfrCode=BAR&MfrPartNumber=1580134&PartType=290&PTSet=A. Got the exact same symptoms, with no change at all.

I only get to work on the car weekends and I have one idea to try this weekend. I believe the water temp sensor is connected to the Air Regulator to provide thoes extra rpms from a cold start. I am going to test that this weekend to see if that is what is malfunctioning. However, I don't see how this would cause the car to die even when it was warm.

 

Anyway, anyone know anything about my problem? I've been studying the EFI manual but can't find much that will help. I havn't tested the control unit yet, but I figure that the connections are good since it actually does something when I connect the wire to the temp sensor.

[Guest De Schmaydee]

which car do you have? .......s

[Guest yTTyTee]

I actually have already solved the problem, it turned out to be an air leak between the throttle body and the AFM. Thanks for the reply though.