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 06:24 AM

Question type: Maintenance & Repair

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

355

And The Kind Of Car Is? PCV Valve? As For Your A, B, C,,, A) Not Likley, EGR Valve???? And EGR Pipes? B) May Be, Look Up The Sensors Ohems And Check It, If Sensor Reads Open!=Bad Sensor C) Did You Just Build The Engine With Out The Use Of A Torque Wrench. NO,, It Would Knock. D)Pray Not!! Mas Air Flow !!....Vaccume Leek?? "B" From Your List? Bad Spark Plug Or Wire? Coil Pack Bad Or Loose? No Ground On Engine Or Nut E-Nuff Ground? Some Cars Have A Counter Balance Shafts Inside The Oil Pan Under The Crank, A Vbrathional Dampner May Have Lost A Ring? What RPM Are You At Going 150 Miles Per Hour? Are Your Tires Ratted For That Kind Of Speed??? No??? Can You Say Blow Out?????

1,545

none of the above. found out it was "b" from my choice... already fixed the problem...

355

Nice! So What Sensor Was It? The World Wants To Know

1,545

the stock oxygen sensor for civic...

1,545

by the way, choice "d" happened before and im glad i always carry a spare...lol!

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