1996 Toyota Camry '96 camry idle drops intermittently when

1996 TOYOTA CAMRY
140,000 MILES • 4 CYL • FWD • AUTOMATIC
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ZEMNIEKS
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Hi,

My '96 Camry started developing and intermittent idle drop about 2 days ago. This happens mainly when the engine has warmed up a bit, and also if it is at normal temp. If I stop the car and have my foot on the break while it is in gear the idle dips about 150rpm or so and goes back up. The dip is enough to feel like a shudder or a misfire. It can hold steady for a few seconds, then dip and come back up, and this can go on for a bit and then stop happening. The car does not stall. If I flip it into neutral or park the idle stays steady and does not drop at all. If I am in gear and it is dipping and I happen to accelerate it at that moment it sometimes feels as though it misses a couple of times when I start the accelleration and then everything is normal. If I am driving around everything is normal and there are no misfires.

What has been checked so far: trouble codes - there were none. Plugs have been pulled & checked. Cap & rotor checked and were ok.

Any ideas on what does this? The rest of the time it starts fine and does not stall!
Mar 26, 2009 at 6:58 AM
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KHLOW2008
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Hi zemnieks,

When idle is erratic, possible causes are :

Vacuum leaks.
EGR system fault.
Ensure proper spark exists from ignition system.
Ensure ignition timing is correct.
Ensure fuel system performs properly (fuel pump, fuel filter, fuel injector and fuel pressure regulator).
Check engine compression, valve clearance, valve timing and timing belt (if equipped).
Check airflow meter or MAP sensor and wiring.
Check Engine Control Module (ECM) and wiring.
Ensure dipstick and oil filler cap are properly seated.

If you are operating the A/C when it happens, it is possible the idle drop happens when the A/C compressor cuts in. This indicates the idle air controls and passages could be partially clogged resulting in the delay in ECM control to bring up the idle speed. Cleaning the throttle body and IAC should solve the problem.
Mar 26, 2009 at 10:13 AM
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ZEMNIEKS
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Hi KHLow2008, that possible list of causes is long but thanks for the list.

I should add the the idle does seem to drop a tiny bit in park, hardly noticeable, but it really is when in gear and with my foot on the brake.

At the end of your note you mention throttle body & IAC cleaning. Is that just for A/C scenario you mentionned or do you mean in general for this problem I should start with a throttle body & IAC cleaning?
Mar 26, 2009 at 11:48 AM
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KHLOW2008
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The list are possibilities so would be long.

The IAC and throttle body controls the idling speed under all conditions. That should be the first thing to do as at the mileage you have, it definitely can do with some cleaning.
Mar 27, 2009 at 10:24 AM
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