first id like to say whats up

my car has a bad idle the idle goes up and down when sitting at a red light and while in park and when u give it 1/2 to 3/4 throttle i hear a knocking sound. but if i floor it the knock goes away..sometimes when i come to a stop and put the car in park the RPM's go to 1000 and slowly drop ...and if i cut the car off right away it desiels like crazy the car runs at a decent temperature..and it has good oil pressure.
the car runs lean and at stop lights i get a check engine light when it sits for a while.

btw its an lg4
thanks for your help
Dan

 

BTTT

 

Dan, when you work on a computer controlled car you have to see what the computer sees or you'll take forever to figure it out. Get a scan tool like Diacom and interface it with your computer. Just knowing what the codes are can tell you a lot. Like if you have a "too lean" code at idle and a high idle speed that's a dead giveaway for a vacuum leak. But you'll throw parts and guesses at it for weeks without knowing what the ECM thinks is wrong.

Also, check your base ignition timing. There's a special procedure to do this. You can't just hook up the timing light and set it. Dieseling is often a sign of over-advanced ignition timing, as is part-throttle knocking.

 

thanks....ill check it out asap

 

Don't bother with the scan tool you can pull codes without one. Bend a paper clip or use a wire to connect the two upper right spots on your computer interface. Turn your key on but don't attempt to start the car. Your check engine light will flash any stored codes.

 

ive heard its really easy to short and fry your computor by doing this. is that true?

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1992 Heritage Z/28
5.7 TPI
Auto Tranny
White w/red stripes
Factory Rear Window Shade
Grey Leather Interior
Alpine CD w/alpine's all around
2 12' subs in custom "camaro" box in trunk
G92 performance package w/ a/c
Flowmaster exhaust
only 14k miles on her!

 

We just went through a similar problem with our 2nd gen Z28. Keep in mind it's carbed, but...Our problem was all timing. We found that the springs for the weights in the distributor were very weak. Bought an advance kit and experimented with the different springs. The real problem was the timing was coming in way to soon and then dropping back out again messing with the idle. After putting in the stiffer springs and setting the initial at 14 we were able to get a full advance of 40 at 2600 RPM. Runs like a top now.

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1984 Z28 350
Never argue with an idiot, they'll just bring you down to their level and beat you with experience
My Web Page

 

Not if you are carefull and only touch the two upper right contacts in the connector while the key is in the off position and then turn it to run, not start, like LFN AT U said.

Ken