Academic Question: Rough Idle on Startup

[CCMphysician]

I have a more academic question about rough idling on startup. When I start the car, on occasion, it takes a split second longer to crank and the idle is initially a little rougher. However, after this, even on a short trip (so the battery hasn't had a chance to recharge), I don't have the problem starting up again. My question is why is the problem so hard to reproduce? Why does this happen rarely?

Thank you,
CCM

[Camry LE 94]

When is the last time you changed the spark plugs, gas filter, etc. Also check to be sure you don't have a vacuum leak anywhere. Check the rubber hoses going back and forth from the EGR valve. Try to recall if you did any work on your car, there might be a possibility you leaned on one of these hoses, causing it to break. And just for future reference, make sure you always post which Gen Camry you have and the model/trim, that way we know what we're dealing with.

[CCMphysician]

1995 Toyota Camry V6 XLE.

Fuel filter has never been replaced, though I have considered it since I am a guy who tends to run the tank to empty. Spark plugs, embarrassingly enough have not been replaced since 60,000 mile mark (I am at 140,000 now). In addition to my regular maintenance log, I also keep a log book of my gas mileage and, noting the absence of any change in gas mileage and the lack of a CEL, have not seen the need to replace the spark plugs.

-CCM

[Mike Gerber]

Does this problem surface when the engine is cold or warm, or both?

Mike

[CCMphysician]

Originally Posted by Mike Gerber

Does this problem surface when the engine is cold or warm, or both?

Mike

I have only noticed the problem when the engine is warm.

-CCM

[justthinking]

I have the similar issue w/ my 96 V6 LE which has just shy of 200k miles...
When start cold, the engine will run a bit rough and RPM is around 1,800 or so, take a while for the car to get warm then everything is again smooth...
Never replaced the gas filter, spark plugs was last replaced at 100k miles (not sure if it was replaced at 160k miles service, need to check it up)

[CCMphysician]

Originally Posted by justthinking

I have the similar issue w/ my 96 V6 LE which has just shy of 200k miles...
When start cold, the engine will run a bit rough and RPM is around 1,800 or so, take a while for the car to get warm then everything is again smooth...
Never replaced the gas filter, spark plugs was last replaced at 100k miles (not sure if it was replaced at 160k miles service, need to check it up)

I've just never had the nerve to replace the fuel filter. Being a firemedic, I often imagine how embarrassing the ironic obituary headline, "Local firefighter killed by his own car fire".

-CCM

[Mike Gerber]

Originally Posted by CCMphysician

I have only noticed the problem when the engine is warm.

-CCM

Then I would try cleaning the throttle body and idle air control valve first. Here's a link with some great pictures on how to do it on the 4 cylinder 5SFE engine. You didn't say which engine is in the car and the majority are 4 cylinders. The V6 is almost identical. Pay particular attention to spraying the cleaner liberally in to the square or diamond shaped hole in the base of the throttle body. That hole leads to the idle air control valve where your problem may exist. Spray down there first and let the cleaner soak 10-15 minutes while you go one to clean the rest of the throttle body.

How to: Cleaning Throttle Body -4 Cylinder Engines- With Pictures

If that doesn't solve the problem, I would next test the engine coolant temperature sensor. You will need a digital volt/ohmeter to do this and the specs from any manual. If you don't have a manual you can download one for free at the top of the Camry forum, over at AutomotiveForums.com. That sensor may be out of range and is telling the computer the car is cold, when it is actually warm. That would result in an overly rich mixture which would flood a warm engine.

Try these things first. They are the most common causes of what you are describing.

Mike