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Idling rough


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brjmhome2
New User

Mar 11, 2008, 7:02 AM

Post #1 of 1 (1580 views)
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The vehicle: 1987 Buick Electra Park Avenue w/3.8L engine & FWD.
Mileage: 183,000
Mileage on new engine: 72,000
Mileage on new transmission 130,000 (was replaced under factory warranty in '92)
Recent new parts: Ignition module, coil pack, plugs, wires, power steering pump, egr valve (which I don't think was needed), lower intake gasket (which I think was a misdiagnosed repair), throttle position sensor, used throttle body, fuel filter (10k ago), all new pushrods, radiator, as well as all coolant hoses.

Problem: Engine runs rough at idle and gets much worse when transmission is engaged (i.e. drive or reverse). Sometimes the engine will stall out when throttle is not open (slowing down for stop lights etc..). When the car is actually in motion the engine runs smooth as silk but as soon as you slow down for a stop light and close up that throttle plate she wants to choke up like there's a vacuum leak. I've thoroughly checked for any & all vacuum leaks & everything is sealed (or so it appears). I've had a mechanic perform a cylinder leakdown test and I was told all cylinders are sealed 100%, no leakage. However in the process of performing the leakdown test, I was told that I had several bent pushrods due to an unknown reason. At this point I had them replaced with all new pushrods & reassembled with no change. I'm told injectors are operating fine with proper resistance as well (replaced w/engine @ 98,000). I"m told fuel pressure is good as well.

The codes: I'm getting a constant EGR flow problem that comes on and off almost always at highway / cruising speeds

The strange: I'm told by my mechanic that the engine runs fine until the computer goes into "closed loop mode". At that point it starts idling rough / shaking....again, this is only with the throttle closed. If you open her up, she sings away.

Extra info: My TCC for my tranny has been unplugged for the 40,000 miles i've been driving the car. I've plugged it back in before & it causes shifting problems so I just leave it unplugged. I have some minor shifting issue like a slow shift from 2nd to 3rd under a light load and when you're coming to a stop and then try to accelerate quickly sometimes you'll feel a really hard shift in the tranny. I'm prepared to overhaul the tranny just due to mileage & the cost to repair the TCC is about 60% of what a full overhaul would cost me so I figure I might as well take care of it all in one shot.

Any ideas would be greatly appreciated,
Thanks,
Brandon

(This post was edited by brjmhome2 on Mar 11, 2008, 7:07 AM)






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