engine idling is out of timing...revs up to 3000rpm and then drops to 1750rpm then back to 3000 again...
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
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
answer is B. I guess Oxygen sensor doesn't work well.
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.
IAC Valve probably.