Camry Bizarre Idle

[damiankaren]

G'day,

The car is an Australian 1999 Camry V6 automatic transmission, MCV20 series 1MZ-FE engine, 200,000km.

The problem is intermittant.

I noticed that after taking my foot off the gas on a flat or down hill road the car did not slow down.

Slip the transmission into neutral at 100km/h(60mph) and the engine remains at 2400rpm. Touch the brake and the engine returns to slow idle. Foot off the brake and the engine returns to 2400rpm.

Let the car slow naturally (without brake and with trans. in N) and engine speed slows from 2400rpm as though it is matching the car road speed.

Let the car roll from stationary down a long hill (trans in N) engine speed climbs with the car speed to 2400rpm as car reaches 100km/h(60mph).

Also, with car stationary with Trans in PARK or N idle is around 1000rpm rather than the usual 750rpm.

The IAC valve is the suspect. I have tested the coil resistances, normal. Checked wiring between ECM and IAC, no problems. Of course, have also checked cruise control, throttle cables, vacuum operated start idle-up. No problems.

When the problem is not occurring I have tried the DLC1 test and the IAC valve behaves normally. Engine rpm increases for ~5seconds then returns to slow idle. When the problem is occurring this test results in no rpm change.

Whether the problem is occurring or not, when stationary, the idle-up as a result of AC on or steering movement appears to work normally.

Otherwise the car is performing normally. Shifting patterns and performance are normal.

Any ideas appreciated.

From reading the forums an IAC clean seems to be the next thing to try. However, I always like thinking about these things for a long time before putting a wrench on the car. :)

Damian.