Warm idle problem, what to do next?

[murphymp]

A lot of info here so bear with me. This is my around town car, but it sucks around town because it won't idle properly. Driving on the highway is no problem.

1994 4 cyl auto with 230k miles. I've had a problem with a random miss at idle for several months. It only occurs when the engine is warmed up. Sometimes the car will stall when I put it in reverse. Running the AC makes it worse as well as being in drive, and I often put it in neutral at stop lights to keep the engine from bogging down too much. You can watch the RPMs drop on the tach and you can see the engine shake if the hood is up.

I've seafoamed the throttle body 3x, replaced PCV, replaced the IACV, replaced coolant temp sensor, took off and cleaned EGR valve, replaced spark plugs, and replaced the engine mounts. The EGR had carbon buildup, but was not completely blocked. Placing a vaccum on it will kill the engine at idle like it's supposed it.

The air intake hose leading into the throttle body has a crack that I've sealed with hi-temp duct tape. Could a cracked air intake hose cause an idle problem? I've searched high and low for vacuum leaks and can't find anything.

I took it a trusted mechanic and had the ignition components checked out. He said spark plugs, wires, and distributor looked fine. A tuneup was done about 20K miles ago. I also took a stethescope and checked the fuel injectors. They all were clicking away like they were supposed to.

Things I'm thinking of doing:
-Replace spark plug wires (about 20K old) ~$40
-replace distributor: new ignition coil was put in about 35K miles ago ~$100
-Replace the EGR valve ($180 ouch!): looks to be origional
-Replace air intake hose ~$35
-Remove fuel injectors and send them off to be cleaned and tested ~$100

I'd like to add that when I run a can of Techron in the tank, the problem disappears for that tank of gas. It will come back when I fill back up.

I realize there are a lot of things that can cause idle problems. Everything I've done so far has done zilch to help the idle problem. I'd like to know what everybody thinks I should try next.

[Camry LE 94]

how's the timing look?

[Mike Gerber]

Just a few thoughts:

"Replace spark plug wires (about 20K old) ~$40"

Were these aftermarket wires? I've seen cheap aftermarkets last as little as 1 year or 20,000 miles.

When you cleaned the throttle body did you spray the cleaner down in to the square or diamond shaped hole in the base of the throttle body? That port leads to the idle air control valve, where your problem may exist.

"It only occurs when the engine is warmed up"

Have you checked the O2 sensors for being in spec? They are out of the loop until the engine warms up and then they start sending signals to the ECU.

I would also check the coil inside the distributor for being in spec? No telling how long an aftermarket coil will last (assuming an aftermarket coil was used 35,000 miles ago), and they too can cause a problem when warm.

One additional thought. Check the engine coolant temperature sensor for being in spec. It also may be out of range and may be telling the ECU the car is constantly cold. This would cause a normal warm up period when the car is cold and a rich mixture is needed. When warm, this mixture may be overly rich, which would explain the problems when warm and the gas small you are experiencing.

Mike

[murphymp]

Mike, thanks for your reply.

Originally Posted by Mike Gerber

Just a few thoughts:

Were these aftermarket wires? I've seen cheap aftermarkets last as little as 1 year or 20,000 miles.

They weren't Toyota OEM, but I don't know the brand. They were tested OK by the mechanic I took it to.

Originally Posted by Mike Gerber

When you cleaned the throttle body did you spray the cleaner down in to the square or diamond shaped hole in the base of the throttle body? That port leads to the idle air control valve, where your problem may exist.

Per the original post, IACV was replaced with a new one.

Originally Posted by Mike Gerber

"It only occurs when the engine is warmed up"

Have you checked the O2 sensors for being in spec? They are out of the loop until the engine warms up and then they start sending signals to the ECU.

I haven't checked the O2 sensors yet. Would I get an engine code if there was something wrong or not necessarily?

Originally Posted by Mike Gerber

I would also check the coil inside the distributor for being in spec? No telling how long an aftermarket coil will last (assuming an aftermarket coil was used 35,000 miles ago), and they too can cause a problem when warm.

One additional thought. Check the engine coolant temperature sensor for being in spec. It also may be out of range and may be telling the ECU the car is constantly cold. This would cause a normal warm up period when the car is cold and a rich mixture is needed. When warm, this mixture may be overly rich, which would explain the problems when warm and the gas small you are experiencing.

Per the original post, the coil was tested by a mechanic and was within spec. I also replaced the ECTS (engine coolant temperature sensor).

How common are fuel problems with these cars? Since the thing runs fine when it has a tank full of Techron, could this indicate a problem with the fuel injectors?

[murphymp]

Originally Posted by Camry LE 94

how's the timing look?

Due to the random nature of the misfire, my mechanic says the timing is fine. The timing belt is only about 40K miles old.

[Mike Gerber]

Sorry for all the miss-information. I was thinking of another thread with a similiar problem.

With 230,000 miles, I guess the fuel pump could be a problem. They are another area that can act up when the car get's warm. Did anyone put a gage on the fuel rail and check the fuel pressure?

Mike

[murphymp]

Originally Posted by Mike Gerber

Sorry for all the miss-information. I was thinking of another thread with a similiar problem.

With 230,000 miles, I guess the fuel pump could be a problem. They are another area that can act up when the car get's warm. Did anyone put a gage on the fuel rail and check the fuel pressure?

Mike

Nothing with the fuel system has been checked. I think the fact that techron solves my problem while it's in the tank lends itself to either an ignition or fuel problem. Since the ignition checks out OK as far as the mechanic can tell, I'm leaning towards checking the fuel system.

I've already listened to the injectors with a stethescope. I'll see if I can locate a fuel pressure gauge. If that checks out, what else with the fuel system should be checked?
Thanks.

[scooter58]

i've been experiencing this same problem,

my car idles really rough like it going to die..
and car runs very rich.

i've been changing a lot of components as well and can't find the problem yet.

[murphymp]

Originally Posted by scooter58

i've been experiencing this same problem,

my car idles really rough like it going to die..
and car runs very rich.

i've been changing a lot of components as well and can't find the problem yet.

Idle problems on this car are a real bi***! For your problem specifically, have you changed the engine coolant temp sensor. If it's malfunctioning, it can create the rich condition your talking about. The sensor is about $15 and takes 5 minutes to replace, at that price it's definitely worth a try.

[scooter58]

Originally Posted by murphymp

Idle problems on this car are a real bi***! For your problem specifically, have you changed the engine coolant temp sensor. If it's malfunctioning, it can create the rich condition your talking about. The sensor is about $15 and takes 5 minutes to replace, at that price it's definitely worth a try.

actually i havent changed that yet, for $15 bucks, worth a try!!
does your idle drop from 800 to about 400-500 rpm's?

[murphymp]

Originally Posted by scooter58

actually i havent changed that yet, for $15 bucks, worth a try!!
does your idle drop from 800 to about 400-500 rpm's?

Yea, that RPM range fluctuation is about right. There are a lot of threads about the ECTS on here. It was one of the first things I changed. Is your idle problem only when the engine is warm, or even when it's cold?

[scooter58]

Originally Posted by murphymp

Yea, that RPM range fluctuation is about right. There are a lot of threads about the ECTS on here. It was one of the first things I changed. Is your idle problem only when the engine is warm, or even when it's cold?

only when it's warm..

[murphymp]

Originally Posted by scooter58

only when it's warm..

Let us know when you change the ECTS and if it fixes your problem.

[whip_cracker]

Stupid question:

Is this similar or the same as a thermostat? If not, does it apply to only the 5SFE?

Interested...

[murphymp]

Originally Posted by whip_cracker

Stupid question:

Is this similar or the same as a thermostat? If not, does it apply to only the 5SFE?

Interested...

The ECTS provides temperature data to the engine computer.

When people talk about thermostats and vehicles, they are usually referring to the thermostat that controls the flow of coolant within the engine.

For more details see: http://auto.howstuffworks.com/cooling-system8.htm