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Car runs Rough, I replaced IPC motor, and car runs the same is it possible the module on the distributor is bad?, sometimes it runs smooth and sometimes it drags and sputters a little especially if I go over 45mph.

Please advise:alchi:
 

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88 Sedan Deville, 89 Eldorado, 11 SRX, 18 CT6
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88 deville eh? Ive got the same one :) ipc motor? do you mean ISC ? if the car runs rough.... is it only at speeds over 45? first the basics...

these cars love clean oil... once it starts to get dark (the 4.5V8) change oil and filter... ive noticed dirty oil can cause rough idle.

second, air cleaner, fuel filter... make sure there both clean... do you frequently let the gas go below 2 gallons?

third... how many miles are on it? are the spark plugs fouled? if its over 100,000 and you have no idea when the plugs have been changed id go ahead and change the plugs. you MAY need wires and a cap/rotor change, but change plugs first if you take any plug out and it seems dirty / bent / just not pretty, change it.

regarding the speed issue.... get on a highway, (one that you can do a MINIMUM of 55...) and get on that exit ramp and give it some good gas, don't baby it. get her up to 55, maybe 65 if you can, and lightly... i mean LIGHTLY lift off the gas, feather it... so you slow down less then 1mph per 4 seconds.... do you notice the stutter? if yes, check EGR valve for dirtyness and replace it. if you only notice it when driving it all gently and nice, check the hoses leading up to the egr, and remove egr... look through the hole is it clogged or any of that fun stuff? if there's cakes of gook all over the egr pintly, you may have luck cleaning it, but id recommend getting an OEM egr valve... DO NOT GET one of those silver craps from a regular store... order the correct egr from a site like www.rockauto.com or www.gmpartsdirect.com that cheap little chineese knockoff will cause your 4.5 to throw a service soon message and will make matters worse at highway speeds... (been there done that lol)

good luck! if you need any help with part numbers, or where parts are, email me [email protected] i can help you out by sending you some pages out of the factory manual

phil
 
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