Car dies when idling in drive but not neutral

Maintenance/Repairs
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1

when my car is at a stop light or just sittin there in drive it dies.it dies only when the motor is warm.it doesnt die right away but the rpms go below 500 and then dies.if its in neutral the rpms stay at about 900 and is fine.

2

That’s a classic symtom of an Idle Air Control valve that’s failing to go to the proper position when the transmission is in gear. The next time it wants to stall when sitting in drive, with your left foot firmly on the brake pedal, slightly tip into the gas pedal. If this prevents the engine from stalling, replace the Idle Air Control valve.

Tester

3

I have the same problem, if its the IAC , why it fails when the car is driven a while , and why it doesnt fail in neutral?

4

The engine experiences more mechanical load when the car is in gear and the brakes applied vs in neutral. So if it was running poorly anyway, the extra load of being in gear could cause it to stall out.

One theory, when you first start the engine in the morning the computer injects more gasoline until the coolant warms up to operating temperature, at which time it reduces the gasoline injected. So if the engine was running on the lean side, a problem would show up more after the computer cuts back on the gas flow; i.e. after it warms up.

5

thank you for your reply, i thought the check engine light would come up for a bad IAC, i have already cleaned up the throttle body and IAC, i currently have three doubts fuel pump, torque converter and IAC. throwing parts is costly, already changed the fluids. unplugged EGR, though the performance was good still felt some engine shaking. Shouldnt the check engine light go off for a bad IAC or any other sensor?

6

I think you meant to ask “shouldn’t the CEL turn on with a bad IAC or sensor?”. In some cases a faulty sensor won’t turn on the CEL. For example a faulty crank position sensor often doesn’t turn on the CEL. I’m not sure if a faulty IAC would turn the CEL on or not on your car. When the IAC failed on my Corolla it didn’t turn on the CEL. We don’t know your accord’s model year btw. Suggest to post this in a new thread, you’ll get better help here. Click on “maintenance/repairs” above left, then “new topic”, above right.

7

Yes I meant CEL on, I have Accord LX 2004,
I tried unplugging IAC valve and rpm went crazy, up and down randomly
Back to stable when connected it back

That’s a good idea I will start a new thread