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rough acceleration under light load- IAC issue??


New Member
Sep 5, 2007
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Members Ride
VS Executive 3.8L
This is kinda similar to Psyko's post - however i couldn't exactly match it to my situation.

I've got a VS, just last month it started playing up - kicking back and forth when going up a hill under light acceleration. Took it to the mechanic, he replaced the module on the transmission. That helped that problem, but now it seems to have really rough acceleration when cruising - eg. cruising down a hill, then going up one and accelerating slightly to maintain speed - its really rough up to about 3000rpm, then after that its fine.

I'm stuck. I've replaced leads, new injectors, cleaned the K&N air filter. Just put a memcal in it as well (thanks Dr Bob) but it was doing it before that anyway.

Seems the longer you drive it, the worse the problem gets, rather than sorting itself out. If you really put down the pedal - once it goes past 3k rpm its fine - sweet as a nut - then when you back off it idles rough.

Been looking at the posts regarding cleaning the IAC valve - not sure whether its this or something else?

Any ideas would be welcome - its driving me nuts.