2004 4L V6 Petrol Prado GX High Idle Problem (Thread 97965)

Submitted: Tuesday, Mar 26, 2013 at 17:00
ThreadID: 101307 Views:3971 Replies:0 FollowUps:0
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Further to post in September 2012 I think I may have solved the problem.
Problem summary - Engine idles at 1200rpm when vehicle is moving but returns to 800rpm when stopped. Replaced water coolant sensor following advice from Toyota - problem remained. Checked & cleaned throttle body - problem remained. Checked IAC - problem remained.

1. Removed both ECU fuses
2. Removed and carefully cleaned MAF sensor with CO contact cleaner and cotton bud as it had a grime build up on one side of the bulb
3. Removed and tested resistance of driver side Oxygen sensor - 7.5 Ohm
4. Removed and tested resistance of passenger side Oxygen sensor - 8 Ohm
Toyota manual says 5-10 Ohm is acceptable. Ellery's manual says 11-16 Ohm is specification. Bosch manual says replace 4 wire sensors every 160,000km or can be damaged by blown head gaskets.
5. Since RH bank blew head gasket and top end was rebuilt, I replaced both O2 sensors.
6. Replace both ECU fuses.
7. Test drive.

So far so good. Hoping the engine will continue to learn over next few days, but returns to idle (800rpm) normally in most cases.

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The sensors are expensive but should pay for themselves in 3 months of fuel savings....

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