02 4Runner rough idle

[iampinoy]

I have a 2002 4Runner SR5 and I am having a little problem with the truck's idle. The tach reads around 600 rpm when on idle (in gear) which I believe is normal but the engine doesn't feel smooth at all. It almost feels like its misfiring. There were a couple of times when the engine almost stalled and I had to immediately move the gear off drive and put it in park to raise the rpm. I checked the MAP sensor for cleanliness and it looks clean to me. I also checked the MAP sensor's plug for proper resistance and voltage, and that checked out ok. I also checked around the butterfly valve inside the throttle body and that did not look overly dirty (I cleaned around it anyway). I took the truck to the dealer but all they can tell me is that they are not getting any trouble codes therefore everything is within specs.

Is there something else I can check that could be causing this problem? Does 2002 4Runners have an Idle Air Control (IAC) Valve that can be checked? Or maybe something in the emission control system?

[Brian R.]

Yes, there is an IAC valve under the air cleaner hose. The resistance between the B+ contact and the other two contacts should be 17.0-25.0 ohms cold or 21.5-29.5 ohms hot. Replace the valve if resistance is not within these ranges.

The EGR system may also be causing a problem.

You may consider cleaning the injectors with Chevron Techron or equivalent in the gas. Check the fuel flow and pressure. New spark plugs and wires may also improve your idle. Check the wire resistance (25K ohms) when you are flexing them a little and see if the resistance jumps.

[forest_grump]

Did you open the *butterfly*/throttle chamber valve and clean the inside of the bore/throttle chamber and edges of valve itself... or clean while it was closed?

Are all you cylinders getting spark and fuel?No vacum leaks?Do you have this problem with and without A/C on?Got good compression and engine not overheated recently??Does stepping on brake effect idle?

Your symptoms are most classicial for a dirty throttle chamber problem and I fear you may not have cleaned it properly...let us know and goodluck

[forest_grump]

Originally Posted by iampinoy

I have a 2002 4Runner SR5 and I am having a little problem with the truck's idle. The tach reads around 600 rpm when on idle (in gear) which I believe is normal but the engine doesn't feel smooth at all. It almost feels like its misfiring. There were a couple of times when the engine almost stalled and I had to immediately move the gear off drive and put it in park to raise the rpm. I checked the MAP sensor for cleanliness and it looks clean to me. I also checked the MAP sensor's plug for proper resistance and voltage, and that checked out ok. I also checked around the butterfly valve inside the throttle body and that did not look overly dirty (I cleaned around it anyway). I took the truck to the dealer but all they can tell me is that they are not getting any trouble codes therefore everything is within specs.

Is there something else I can check that could be causing this problem? Does 2002 4Runners have an Idle Air Control (IAC) Valve that can be checked? Or maybe something in the emission control system?

Did you open the *butterfly*/throttle chamber valve and clean the inside of the bore/throttle chamber and edges of valve itself... or clean while it was closed?

Are all you cylinders getting spark and fuel?No vacum leaks?Do you have this problem with and without A/C on?Got good compression and engine not overheated recently??Does stepping on brake effect idle?

Your symptoms are most classicial for a dirty throttle chamber problem and I fear you may not have cleaned it properly...let us know and goodluck

[Brian R.]

Here's a link on how to clean a throttle body on a different engine.

http://www.4x4wire.com/toyota/mainte...throttle_body/

[iampinoy]

Originally Posted by Brian R.

Yes, there is an IAC valve under the air cleaner hose. The resistance between the B+ contact and the other two contacts should be 17.0-25.0 ohms cold or 21.5-29.5 ohms hot. Replace the valve if resistance is not within these ranges.

The EGR system may also be causing a problem.

You may consider cleaning the injectors with Chevron Techron or equivalent in the gas. Check the fuel flow and pressure. New spark plugs and wires may also improve your idle. Check the wire resistance (25K ohms) when you are flexing them a little and see if the resistance jumps.

Thanks for all the suggestions and information. Yes, I opened the *butterfly* valve inside the throttle body and cleaned the chamber and edges of the valve. I also replaced all the spark plugs, measured the resistance of the spark plug wires, measured the resistance of all the ignition coils, and changed the air filter. ##I am not sure though how to check for vacuum leaks.## The idle improves when the A/C is on and I think that is because the idle speed increases slightly when the A/C is turned on. The engine has never overheated (only has 40,000 miles). There was a time when it felt that the idle worsen slightly when I stepped on the brakes and sometimes felt as if it was going up and down a bit when the turn signal was on (up when the turn signal light was off and then slightly down when the turn signal was on). However, it is not doing that now. I can feel vibration on the steering wheel and driver seat when the truck is at idle (with gear engaged). The vibration is a consistent type and not random or goes up and down.

[iampinoy]

Originally Posted by forest_grump

Did you open the *butterfly*/throttle chamber valve and clean the inside of the bore/throttle chamber and edges of valve itself... or clean while it was closed?

Are all you cylinders getting spark and fuel?No vacum leaks?Do you have this problem with and without A/C on?Got good compression and engine not overheated recently??Does stepping on brake effect idle?

Your symptoms are most classicial for a dirty throttle chamber problem and I fear you may not have cleaned it properly...let us know and goodluck

Thanks for all the suggestions and information. Yes, I opened the *butterfly* valve inside the throttle body and cleaned the chamber and edges of the valve. I also replaced all the spark plugs, measured the resistance of the spark plug wires, measured the resistance of all the ignition coils, and changed the air filter. ##I am not sure though how to check for vacuum leaks.## The idle improves when the A/C is on and I think that is because the idle speed increases slightly when the A/C is turned on. The engine has never overheated (only has 40,000 miles). There was a time when it felt that the idle worsen slightly when I stepped on the brakes and sometimes felt as if it was going up and down a bit when the turn signal was on (up when the turn signal light was off and then slightly down when the turn signal was on). However, it is not doing that now. I can feel vibration on the steering wheel and driver seat when the truck is at idle (with gear engaged). The vibration is a consistent type and not random or goes up and down.