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Discussion Starter #1
On my '89 Mercury Sable, I have recently experienced some problems with acceleration as well as idle. Basically, sometimes when I am accelerating or just have my foot on the gas, the car "bucks" as if a big monster is momentarily grabbing onto the rear bumper and letting go repeatedly. It is not the fuel filter, injectors, pump etc. Also, occasionally when I put it back into park after driving, the engine will rev to 2000 rpm. Sometimes when I drive the car it is fine, but others it will exhibit these problems. These symptoms point me toward the EGR valve, but I was wondering if anyone knows any symptoms of a faulty EGR valve. The '89 is equipped with a pressure feedback electronic (PFE) EGR valve which essentially uses vacuum to operate. If the valve was malfunctioning, could it produce these symptoms? Any help would be greatly appreciated.

Thanks,

Jeff
 

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On older EGR valves they came on higher up in the rpms(2500) and it would make the engine run realy lean. It made the enigne shake like jello in an earthquake.
 

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Interestingly enough, I notice it most often around 1600 rpm (~45 mph). Sometimes when I get up to 1600, it will start bucking, whereas other times, the car will accelerate by itself to around 60 mph. Could this still be EGR related? I plan to run some diagnostics on it either today or tomorrow, but I'm trying to save myself time because I leave town on Sunday to head back to school.

Jeff
 

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Pull the trouble codes. That will atleast point you in the general direction of what is malfunctioning.

I have just been doing a lot of work on my cousins EGR system in her Mercury Topaz. I posted here about it a few days ago (do a search for EGR or PFE), you might want to take a look at it to see if any of what I experienced is relavent to your problems. Good luck!
 
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