engine idling is out of timing...revs up to 3000rpm and then drops to 1750rpm then back to 3000 again...

1,545

Asked by Dec 06, 2011 at 06:18 AM

Question type: Car Customization

my revs are not in sync...the idle rev rises and drops...when AC's on, it stays on 2500rpm...and when i engage to Drive (AT
gearbox), it stays on the 1500rpm idle...i checked the block and the crankshaft is okay and everything is in place...what could it
be? probabilities:
a.) clogged intake manifold
b.) defective air sensor
c.) lose-thread pistons and crankshaft
d.) loose timing belt

when in cruising speed with AC it seems to run fine but when AC's off and i reach about 140-160mph, the engine shakes and idle
is crazy...

5 Answers

25

answer is B. I guess Oxygen sensor doesn't work well.

1 out of 1 people think this is helpful.
15

b

1,545

yeah i had to change the sensor and clean the manifold...then took me a few tweaks to fine tune the idle coz it was a bit higher than the desired rpm...

I.A.C. idle air control is either defective,or is not conected properly.

985

IAC Valve probably.

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