My 90 L98 automatic after driving awhile at hiway speeds will throw a code 32 ( egr system) and go off when shut off until next time driven at steady 50 plus mph. Car runs fine and shows no difference when code appears yet it's there, any thoughts or common symptoms / repair suggestions? Thanks in advance....

 

Very common issue, the EGR is not activated until you've been cruising at operating temps above 170F, so its mostly just running on the highway. It is not something you should be alarmed about, as it doesn't impede the engines performance.

FSM has a troubleshooting diagram, which usually points to solenoid/switch problems. Follow the manual procedure.

 

Thanks, the EGR was replaced app. 25,000 mile ago and still looks new, is the solenoid a hard to replace item? Might just throw one in to see?

 

I had the exact same symptoms in my 1985. My EGR valve was the culprit. I also changed the EGR switch while I was there, but they got rid of the EGR switch in 1990 so you don't have to worry about that. 25,000 miles is not a lot of miles on your EGR valve, but it is conceivable that it could have failed already.

I'd check the EGR solenoid, also. On 85-89's, the EGR solenoid is easily accessible and easy to check (mine was OK), but I don't know where they moved it for 1990.

 

I had the same issue, my mechanic replaced the egr valve first still had the same code, he replaced the egr temperature control switch, solved the problem the switch is still available out there for c4 1986-1990

 

Thanks guys..............Does anyone know where the EGR solenoid is on the 90?

 

Here are pictures from a 1990 FSM. They claim you need to remove the plenum to remove the EGR Solenoid. I don't know if that's true for a 1990. You don't need to remove the plenum on my 88, and the 85 EGR Solenoid is on the other side of the engine.

 

The EGR system on the 90 is the same for 91.
The solenoid is located on the rear mounting bolt for the thermostat on the intake manifold.

I have had two EGR solenoids fail and cause 32’s. I got tired of digging under the plenum, so I relocated the solenoid to the bolt on the AIR pump.

First, check your spaghetti lines for the entire EGR route. Mine were old and brittle and kept breaking. I pulled all new rubber lines. You do not need that little manifold on the solenoid - it just keeps track of the hose routing. I eliminated mine and just plugged my vacuum lines directly to the solenoid.

Recall your system has ported vacuum. Before you start yanking lines, make sure you document where they start and finish.

The EGR solenoids are not cheap.

Some experts say a malfunctioning EGR system can potentially damage your engine because the ECM provides the wrong fuel/air mixture assuming you have inert gas mixed in the cylinder when, in fact, you will have oxygen rich air causing a lean mixture. I cannot validate that statement but it does make sense.

I keep my EGR functional because it seems like a free lunch to me: when you don’t need to burn the extra fuel, you don’t. When you mash the gas, the EGR cuts off and does not influence performance. Sounds like a good deal to me.

Fascinating and creative system, if not problematic.