Car starts but won't idle, has a miss when running.

3.8

Registered User
1990 SC 5 speed

Hey guys, this is 3.8's girlfriend posting for him because he is at work. Last night his car ran fine when he parked it. This morning when he started it, it would rev to about 1,200 RPM for about a second then the car dies. He could restart the car and keep it running using the gas pedal. When he was driving to work the engine had a noticable miss, it kind of had a chug-chug to it. After he got to work and the car warmed up a bit it would idle, but was idleing rough and still missing out.

Last night we had freezing rain and snow and it was 14 degrees this morning.

Where should he start?



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Sounds like the symptoms of a cam sensor. Look to see if the tach starts becoming erratic.
 
He might also want to pull codes whenever he can. It almost sounds like when the MAF sensor isn't hooked up (he could try unplugging it and plugging it back in). But again, the codes might give some direction.
 
Given the symptoms, there are a lot of possibilities (both above are possible probs) Definately start with a scan. If there is a prob with the cam sensor or DIS module, the tach will start acting up. High moisture can also wreak havoc with the ignition system if there is bad insulation or loose connections on any components.
 
Another common prob : Old and worn ignition wires that are fine in good weather will start causing spark problems when it is damp and cold. If the wires are still original, you might want to consider changing them if nothing shows in the scan. If you do change wires, use KEM. They use a re-designed boot cover that gives a much more positive lock to the coil pack then the oem two tab style.
 
Ok... I looked around under the hood for obviously loose connectors and vacuum hoses and found none. I started the car and it ran rough and would barely idle. I also noticed the vacuum gauge was around 12 at 800 rpm when usually it would read about 21 or 22.

The car idled for maybe 2 or 3 minutes from a cold start (it's 20 degrees outside) when I noticed the metal tube (red arrow in pic below) was so hot I couldn't touch it :confused: I gave up and shut the car off to go in wash my hands. Then I tried to start the car and it finally started and ran rough for a few seconds and then started running fine and my vac gauge was back to a little above 20. It ran fine the entire 17 mile trip home. When I got home I toughed the metal pipe that was hot earlier and it was cool now...

What could make that pipe get so hot I couldn't touch it after idling the engine for just a few minutes? What position should the linkage (blue arrow) be in when the enging is at an idle?

I'm going to go search soon on how to get my codes, if there are any.


2-14-07.jpg

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The blue arrow is a bypass valve that opens at idle, so that linkage should be opened about 90 degrees from the point of the set screw.

If the bypass valve isn't opening then the air will route through the blower and intercooler before it gets to the motor. This will make everything too hot to touch. If it isn't opening then there is a small vacuum line that goes to the diaphragm (the circular, black device the opens and closes the valve).
 
The engine is off in the pic. The bypass valve appears to open at idle.

I'll wait and see what happens in the morning when I try to start it, it's supposed to get down to 10* here.



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