Rough Idle during Warming Up

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ZR - 27 Dec 2006 22:29 GMT

I have a 1990 Camry. The idle is very rough during warming up. Engine speed
would suddenly increase to very high for a few seconds and drop back to near
stall. It will repeat this before it's completely warned up (20-30 minutes
of driving in cold days). The engine will stall if this (surge and drop)
happens during acceleration. It only happens during warming up. It does not
happen if the engine is completely cold (first couple of minutes of cold
start) or completely warmed up (hot).

Does any one have any suggestions where I should start?

Thanks for any help!

Have a nice holiday!

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Ray O - 27 Dec 2006 23:12 GMT

>I have a 1990 Camry. The idle is very rough during warming up. Engine speed
>would suddenly increase to very high for a few seconds and drop back to
[quoted text clipped - 9 lines]
>
> Have a nice holiday!

The engine should not take 20~30 minutes to warm up. Check the coolant
temperature sender to see if it is operating properly. Also check to see if
the thermostat is stuck open and check EGR operation.

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Ray O
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ZR - 27 Dec 2006 23:30 GMT

>>I have a 1990 Camry. The idle is very rough during warming up. Engine
>>speed would suddenly increase to very high for a few seconds and drop back
[quoted text clipped - 13 lines]
> temperature sender to see if it is operating properly. Also check to see
> if the thermostat is stuck open and check EGR operation.

Thanks, Ray. The engine temperature gauge seems working properly. It only
took a few minutes to reach the middle. I meant it took about 20-30 minutes
for the problem to disappear, at which point it seems the engine compartment
is warmed up and the engine is "hot" (in the sense of normal hot). I'll
start checking those items.

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Ray O - 28 Dec 2006 04:16 GMT

>>>I have a 1990 Camry. The idle is very rough during warming up. Engine
>>>speed would suddenly increase to very high for a few seconds and drop
[quoted text clipped - 19 lines]
> compartment is warmed up and the engine is "hot" (in the sense of normal
> hot). I'll start checking those items.

OK, it seems like the engine is actually warming up. Check the black
plastic intake snorkel between the air filter housing and the throttle body
for cracks, holes, leaks, etc. If there are any holes, use duct tape to
seal them up.

I don't remember what kind of air flow sensor the car has, but I think it is
the MAF type. The MAF sensor will be located on the air filter housing and
will have a tube that sticks out into the air flowing into the snorkel.
Inside the tube is a thin wire that gets coated with gunk over time.
Carefully clean the wire with rubbing alcohol or carburetor cleaner and a
Q-tip. The MAF sensor is not supposed to be serviceable, so you have
nothing to lose by cleaning it. If the air flow meter is the flap type,
make sure the flap moves freely without hanging up.

One other possibility is the idle air control valve on the throttle body may
be hanging up. Carefully clean it with carb cleaner.

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Ray O
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ZR - 28 Dec 2006 05:11 GMT

>>>>I have a 1990 Camry. The idle is very rough during warming up. Engine
>>>>speed would suddenly increase to very high for a few seconds and drop
[quoted text clipped - 20 lines]
> body for cracks, holes, leaks, etc. If there are any holes, use duct tape
> to seal them up.

It looks good and there is no cracks or holes.

> I don't remember what kind of air flow sensor the car has, but I think it
> is the MAF type. The MAF sensor will be located on the air filter housing
[quoted text clipped - 4 lines]
> have nothing to lose by cleaning it. If the air flow meter is the flap
> type, make sure the flap moves freely without hanging up.

It's the flap type, and it's working properly.

> One other possibility is the idle air control valve on the throttle body
> may be hanging up. Carefully clean it with carb cleaner.

I did more testing and remember I had similar "surge" on highway doing 60-70
MPH. It happened on local road too recently. So it looks like it will happen
even after completely warmed up. It's just less often than during warming up
and just warmed up.

I also googled this problem. Most points to EGR Valve. Can the EGR be
cleaned somehow or it has to be replaced?

Thanks again!

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Ray O - 28 Dec 2006 18:45 GMT

>>>>>I have a 1990 Camry. The idle is very rough during warming up. Engine
>>>>>speed would suddenly increase to very high for a few seconds and drop
[quoted text clipped - 46 lines]
>
> Thanks again!

The EGR can sometimes be cleaned although replacement is usually more
effective. To see if it is the EGR valve, temporarily disconnect the vacuum
hoses from the EGR valve and plug the hoses with a golf tee or screw and see
if the problem clears up. If the problem does clear up, either the EGR
valve is hung up in the open position or the vacuum switching circuit is not
working correctly. You will need a repair manual to check the various
vacuum switching control valves. You can remove the EGR valve and see if
you can see any buildup around the valve sealing surface.

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Ray O
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ZR - 29 Dec 2006 03:02 GMT

> The EGR can sometimes be cleaned although replacement is usually more
> effective. To see if it is the EGR valve, temporarily disconnect the
[quoted text clipped - 5 lines]
> EGR valve and see if you can see any buildup around the valve sealing
> surface.

I tested the EGR system and it's working fine.

It turns out it's actually the distributor cap and rotor. They were worn
out. I recently replaced the distributor, but not the cap and rotor because
they looked like new, even though there were replaced long time ago. I
replaced the plugs, wires, cap and rotor, and it's working fine now.

I was mislead by the fact the engine would "surge" from time to time. It's
strange that the engine would surge (instead stumble) on this car if the
ignition system misfires.

Thanks for the help!

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Ray O - 29 Dec 2006 03:46 GMT

>> The EGR can sometimes be cleaned although replacement is usually more
>> effective. To see if it is the EGR valve, temporarily disconnect the
[quoted text clipped - 19 lines]
>
> Thanks for the help!

You're welcome, although I didn't contribute much to the solution!

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