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Discussion Starter #1
Have a 1998 RAV4. Manual. Runs ok overall, but sometimes at idle sounds like one cyl isn’t firing.

But the real problem is that after starting a warm engine - like after fueling up, after about 15 seconds the engine will lose all power. It will still idle; but can’t be drive. Literally no response to throttle.

The fix, we have learned, is to keep trying to rev it in neutral, and 30 seconds later or so the problem might just go away.

I’ve replaced the EGR valve ( several times), as well as modulator.

Any help would be appreciated!
 

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Here is where I would start:

-- Is the computer throwing any codes, either at present or pending? Autozone will read your computer for free.

-- When was the last time the plugs and wires were replaced?

-- Check the ECT sensor's resistance:


-- Check that the front oxygen sensor is properly connected.

-- Check that the crankshaft position sensor wiring appears intact. Disconnect and check the resistance of the crankshaft position sensor. Crankshaft position sensor resistance specs:
985-1600 ohms when cold
1265-1890 ohms when hot
 

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Read the OBD-II codes even if no CEL -- what are they?

A major tune up anyway: plugs, wires, cap/rotor if so equipped, air filter, and underhood fuel filter. Replace the water temperature sender too (cheap/easy).

After those, could be one of many things. Try loosening the gas cap -- cure the problem? Might need a new cap, or fuel pump.

Maybe replace the ignition coil(s) too. And upstream oxygen sender (time anyway).

Mine sort of acted that way when the timing belt was jumping. A bad IAC valve also wouldn't let it idle well.
 

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Discussion Starter #4
Thanks! No cel and no codes. We got new plugs and wires, but really seems related to some cold start/warm start mechanism. For what it’s worth, temp sensor also slightly below normal even after lots of driving.
 

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For what it’s worth, temp sensor also slightly below normal even after lots of driving.
As indicated by... ? Do you mean the sensor's resistance is slightly below normal, as measured with a multimeter?

The front oxygen sensor signal is used only after the engine is warmed up. If the oxygen sensor is faulty, the engine will not run well after warm-up. Sometimes a bad oxygen sensor will cause the computer to throw a code; sometimes not.
 

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-- The rear oxygen sensor only monitors the catalytic converter. It's the front oxygen sensor that may be the problem.

-- After warm-up, the temperature gage in the instrument cluster (dashboard) normally reads a tad below the halfway mark. Once warmed up, the needle on the temperature gage should not move.

-- The ECT sensor does not provide the signal for the temperature gage on the instrument cluster. Here's a photo of the ECT sensor's location:

Above, engine coolant temp sensor = ECT sensor
 

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Another possibility: clogged cat converter.
 
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