My mark 7 is idling really high and popping really loud and bad when i let out of the gas goin down the road. First i thought it was valve seals cause the exhaust is cut off, but its not smoking.

Asked by mahaffeykyle Jul 23, 2012 at 09:03 PM about the 1990 Lincoln Mark VII LSC

Question type: Maintenance & Repair

I recently cut the exhaust off cause my cats and resonators were busted out on the inside and making annoying
racket sounds. I have been driving it with the exhaust cut off for a while. All of a sudden going down the road
whenever i would let off the gas it would pop REALLY loud. Now it did it before anyway cause the exhaust was
cut off, but now it does it worst. And while in park or at a stop sign or red light it idles high. At first i thought it
would be a blown valve seal, but as far as I know if the seal was bad or blown it would be smoking....and its not
! A buddy of mine told me it could be a vacuum hose is busted or slipped off somewhere. Could it be that....or
what else could it be ?

865

shortboxdan answered 12 years ago

running that engine with out the cats or exhaust cut off real close to motor can cause that computer to pick up a real lean condition which also tell all the sensors to act funky.. u possibly could have sucked a valve but that wouldnt cause high idle more of a miss, a high idle is like avacuum leak which could be just a simple hose or intake gasket or something close...spray carb cleaner all around engine to see if it idles down or differen then concentrate spray in that area till u find what could be the cause

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Andrew answered 12 years ago

running straight pipes with no muffler or cat has it's risks. The closer the exhaust is cut to the motor the worse it can be. There are possiblities that cool air can enter the exhaust and crack the manifold, head, block, or damage the valves. I would suggest slapping some kind of exhaust on there soon even if no damage has been done. shortboxdan said the O2 sensor may be reading lean now and that's correct. Could be dumping more fuel in the engine and you should smell this due to the lack of a cat or any exhaust casue it would run real rich. High idle is usually a sign of vacuum leaks or a bad TPS sensor. Try unpluging it while the car is running to see if it makes a difference, it should.

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