EGR Valve Grrr!!!

[cavediver]

Ok,

I've been getting a code 32 from my 94 Q45 since last year. Code 32 is a EGR valve malfunction. I have:

Replaced the vacuum lines Replaced the EGR solenoidReplaced the EGR ValveReamed the EGR tube

....and still the code 32 intermittently comes on... Ideas anyone?? Q45 Tech?? RU still out there?

Could it be the EGR temp sensor (even though that should give a different code)???

Cdiver

[DAEDALUS]

Codes only tell you what the vehicle thinks is the most likely suspect from inputs that can vary. EGR temp sensor code tells you if the temp sensor is open or shorted. But what if it's just non-responsive? ECU only sees black and white. See the FSM. Measure sensor voltage with the engine idling. Should be < 4.5 V. Use a hand vacuum to lift the EGR, but don't kill the engine. Voltage should fall to < 1 V. If sensor passes, go back and diagnose the other components again. You have to fake it sometimes, put words in the ECU's mouth.

[Q451990]

Have you checked for carbon blockages in the EGR tube and plenum?

Heath

[CJQ45]

BINGO!!!!

I think you hit it right on point. I had a similar problem - clean clean and clean your BPT and intake! I was getting the temp sensor code. Turned out that the temp. sensor was ok - just the flow of air above it was restricted to give the wrong voltage reading.

CJ

[cavediver]

If I spray carb cleaner through the EGR port directly into plenum - do I risk damaging something?

Thanks,

CDiver94 Q45

[Q451990]

Doubtful... but it typically takes more work than that... like a dental pick with the plenum removed. if nothing else, pull the temp. sensor, soak the port with brake parts cleaner, pull the EGR valve, and try cleaning it with a shotgun brush or something like that...

Ultimately, I think you'll end up pulling the plenum though. Then it's time to think about all new hoses, knock sensors, ohming the injectors to look for likely failures, etc...

Heath

[DAEDALUS]

Before spending time disassembling things, lift up on the EGR and see if the engine stalls. If it does, clogging is not your immediate problem, unless the sensor itself is completely fouled up--pull it and see. Assumed you did this lift-test before you replaced all that other stuff, since it's one of the first steps of troubleshooting the system.

[cavediver]

Thanks guys. Yeah, I did do the EGR stubble test and both the old EGR and the new EGR valve stalled my Q.

Pulling the P, well, I've done that twice (the most recent was last summer) and I would rather have extensive and painful dental work done before I do a P job in the near future.

From here, I think will try replacing the BPT valve, since Joe sez its only around $30.

Thanks All,

Stephen aka "Cdiver" 1994 Q45

[DAEDALUS]

Measuring voltages is free.

I keep stressing in this forum that throwing parts at a problem is usually not a good method of troubleshooting things, especially if the parts are used. You could unknowingly get 2 bad parts and rule out something early on, to be followed by lots and lots of frustration. Plus throw in the ambiguities of the trouble codes. "Dumb as rocks" I think is what Dennis calls the ECU.

[PoorManQ45]

Before spending time disassembling things, lift up on the EGR and see if the engine stalls. If it does, clogging is not your immediate problem, unless the sensor itself is completely fouled up--pull it and see. Assumed you did this lift-test before you replaced all that other stuff, since it's one of the first steps of troubleshooting the system.

what do you mean bby "lift up the EGR"?

Does that just mean disconnecting the EGR should cause the engine to stall? If so, I thought the EGR was only there to help increase mileage at cruising speeds and lower emissions. I didn't know it was mandatory for the engine to run

[3Q Jay]

what do you mean bby "lift up the EGR"?

pull open the valve by either pressing the diaphragm against the spring, or using a hand vacuum to partially open it. if you open the EGR valve very far with the engine idling, the relatively high ratio of exhaust into the intake will cause stumbling or outright stall.

[cavediver]

Good advice, but when the cost of the part is relatively small ($30) buy it and stick it in.

I tend to replace parts before they go bad if I have I'm doing a big job and have the engine in small piles on the parking lot. It saves me the time from having to continuouly work on my Q.

Cdiver