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I am kind of stumped.

I have a 1996 Toyota Rav4 that is acting weird. Let me start with the list of recent repairs.

I gave it:

  • a tune-up (new sparks, wires, distributor cap and rotor)
  • changed the radiator
  • cleaned the EGR valve, and
  • recently changed the thermostat.

After all this the engine started revving up and down when idling. If I try to drive the car while it is still idling it stalls a lot. However the car still stalls a bit when it is finally warmed up but not as frequent nor as hard.

I started looking on the web what it could be and still no luck. So far I have:

  • cleaned the throttle body and the IAC valve
  • installed a new PCV valve
  • checked for vacuum leaks via a smoke test and the sparking carb cleaner method - I just tried a new MAP sensor.

The only check engine light codes the car throws are P0300 and P0301-4.

Anyone have any idea what it could be?

Resolved (11/15/15): It was a loose camshaft position sensor. Plugged it in and now the car runs fine.

emmanvazz
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2 Answers2

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Quite often surging like this is caused by not enough air getting passed the butterfly valve in the throttle body when the butterfly is closed. Under normal circumstances, there should be a very small gap around the butterfly to allow the air required for idle. If the butterfly is closed too much, the revs will drop too far forcing the engine ECU to open the idle control valve (IAC). It will then try to back off the air through the IAC, but since not enough air is getting passed the butterfly for idle, the revs will drop to far and so the surging cycle repeats.

Either the throttle body internals are dirty, which you say you have already cleaned, or the throttle just needs adjusting due to wear. There should be an adjustment screw on the throttle body that should allow you to open the butterfly valve slightly. Hopefully this will stop the surging.

HandyHowie
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I have a 1996 CR-V. Have been reading around the net for fluctuating RPM at start. When I read what you changed. There is a similarity. Mine started after I put in a new thermostat. I am going to take a look at the thermostat. You try that too.

JohnChing
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