Its an '89 Iroc with L98. I was setting the timing and noticed the EGR selonoid was disconnected. I owned the car for 2 years and I know I didn't leave it off. However, since I first got the car it shakes kind of roughly at idle even though the tach only bounces around by 50 RPMs or so. When it gets hot like around 200 degrees it starts to shake even worse and the idle drops some. When I set the timing I noticed that when it shook the timing jumped around a bit. Well I reconnected the selonoid and it didnt help. The funny thing is that I never got a code. I know the SES light works because I had the car in diagnostic mode to pull the codes and all I got was a 12 which is normal. On a side note I had the IAT sensor disconnected to and I got no code but I do get one for bypassing the EST to set timing, MAF, etc.. I am using the stock PROM. I was thinking that the EGR was stuck but the diaphram can be moved but it is tight. I couldn't get my fingers under the plenum to try and move it while the car was together and running though. The vac lines from the TB to the selonoid to the EGR look good and I sprayed all around with carb cleaner and the idle was not affected. The car has fresh plugs, wires, and coil. The original engine only has 60K miles on it and has good power and does not burn oil..no blue puff on startup eighter. It is a summer only car and sits in a garage during the winter. It is started regularly and the stabilizer is added to the gas.
Well my questions are:
1)Why no SES light when the selonoid was disconnected for so long? (Yes I do do a lot of highway driving so the EGR should have been called upon)
2)Why does the car shake at idle?
3)Why does the timing jump when the car shakes?
4)What can be effected by letting the car sit the 4-5 months for winter? Injectors..?
Thanks!!

 

Anyone?

 

EGR on MAF cars is a funny thing... rarely will it set a code for it.

It sounds like an ignition problem. I'd check the wires out, and the pickup coil.

 

Wires are brand new but how do I check the pickup coil? Where is it at and how to I get it off the car........please be detailed. How much do they cost?

 

you can disconnect just about everything on a TPI car and it will run fine.

don't count on carb cleaner to show up any vacuum leaks on an EFI car. Better to use starter fluid (ether) or propane from a torch.

rough idle could mean a lot of things but usually the IAC motor/valve is the culprit....
and yes you can unhook that too and the car should run fine (better in most cases I've seen).

 

I've also cleaned the IAC passages and the valve itself and it still has a shakey idle.

 

nice name, I wanted to get LKEAROC on my license plate but somebody already stole it...oh well

------------------
90 IROC 5.7l (L98)
ram air, K&N's, air foil,Flows

LIKE A ROC

 

The code for the egr is set from the temp switch mounted in its base.

If it jumpy at idle maybe the egr is bad and it is flowing at idle, but since the switch is hot it won't set a code even if it's diconnected.

'could be' or one of the many other things it could be.

 

btt........