EGR Valve and chasing rough idle 94Q

[daegrigg]

I am gradually working through a newly acquired low-miles 94Q (72K miles) that sat for several months. I have read many, many, many threads.

Idle is rough but the car has no hesitation and accelerates smoothly. Idle issues seems below about 1500 -2000 rpm. There does seem to be a "dead spot" in partial throttle opening for acceleration.

What I've done so far:

Visual check for loose hoses and connectionsCleaned MAF - with CRC Intake cleanerCleaned Throttle plate with the same (use about the whole can on both)Changed fuel filterRan a tank full with BG stuffFuel pump in trunk is silentInjectors are firing (mechanic's stethoscope), i.e., I can hear the click, click, click, except 5 and 7 which seem impossible to get to with plenum on,

Now, EGR valve question.

One post mentioned a bad EGR valve as possible idle culprit. I can push the diaphragm from the bottom and there seem to be about 1/2 to 1 inch of travel. When I do this manually with the car running, it practically stall the engine. However, when I blip the throttle, the diaphragm hardly moves on its own. Does this mean anything.

Next step if the EGR is good, is to check the coil covers/connections and change plugs.

Any other advice suggestions.

Thanks for your patience, I realize this topic has be discussed many times.

Don


Modified by daegrigg at 8:19 PM 8/3/2005

[maxnix]

Did you clean the tube from the EGR valve?

Have you cleaned the IAC valve?

[Meaux]

I had the same symptoms, I did everything you did, (except the fuel filter) adjusted this and that. Thought I had a EGR problem also...When I got the FSM and ran the Diagnostic 2, I got the (34) Knock Sensor code.

I'm now in the process of pullin the plenum to replace the KS's, I can only do so much with it raining every five minutes...This is taking forever...:-(

Have you ran the Self-Diagnostic 2 yet?

My 94Q has 78K on it.

Good Luck and let us know what you come up with...I know I'm curious...:-)

[DAEDALUS]

The EGR is not supposed to function at idle or acceleration. Problems occur if the EGR valve is leaky. Even then, it is more likely to cause the sluggish performance rather than roughness (from running rich). Unless the EGR gasket is letting air in, it isn't the first thing I would suspect.

[daegrigg]

Read a lot of thread but haven't found specific instruction on how to run the Self Diagnostics on my 94. Are they posted somewhere. Do not yet have a FSM.

Thanks,

Don

[rsiwicki]

Quote »The EGR is not supposed to function at idle or acceleration. [/quote]EGR functions from around 45mph to 60mph....not anywhere below 45mph or above 65mph.....how do I know one might ask??? I have custom headers which deleted the EGR thingy. I have been running with the EGR pipe capped off for the last 1+ years and after a solid 15,000 miles I only get the EGR check engine light when I am stuck on the roads going between 45~60mph. I can cruise at 70+mph for hours or drive around downtown during lunch etc and never get the EGR CEL. I don't have any idle problems unless you call idling at 550rpms a problem...don't know why car idles at 550rpms, but it does so nice and smoothely with 156,000 miles and counting.

Interesting thing is that many of the newer cars I have been looking at don't have an EGR...the computer can monitor adjust the changes per cylinder so quickly that the EGR is no longer needed on some of the more advanced engine management systems.

[DAEDALUS]

The EGR has never really been a necessity anymore than charcoal cannisters or oxygen pumps have. It's an emissions device that lowers combustion chamber temps to reduce NOx. It has the side benefit of increasing mileage during cruise by allowing the engine to waste less energy during the intake strokes. Don't know what they would use in place of the EGR system. I'm only as hip to car tech as my '90 Q and '95 Dodge. I'm just thrilled they're both fuel injected.

[maxnix]

I remember engine driven air pumps for the exhaust on SBC. Very kluge.

Made CVCC seem very high tech. Members don't realize how advanced 4 valve DOHC heads, port injection, computer controlled cars are.

[Meaux]

Try this out........

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