Wont idle but runs fine. Any Ideas ?

[Jason11]

Wont idle but runs fine. Any Ideas ? -- [Solved !]

Hey guys. So I just purchased a 2000 3rd gen. 4Runner. 250K miles and on the way home it misfired and started running poorly. I suspected bad gas because the previous owner has the truck sitting for months. The check engine light came on and threw code P0171 and P0171P.

So...I decided to do a bit of maintenance.

Put in a new fuel filter
new plugs (NGK)
new wires (NGK)
new air filter
cleaned the MAF with CRC MAF cleaner.
(During the fuel filter change I unplugged the EFI relay)

got everything back together and started it up last night and... it started perfectly. I let it idle for a few minutes and it sounded/felt perfect. Great. So I took it out for a test drive down the street and it ran great, no problem. Gave it some gas and revved it up to redline and it felt great, no misfire or anything like that. It had good power, so I thought the problem was fixed. Then I came to a stoplight and as I slowed down towards idle it idled really low and then died. I turned it over a few times and it wouldn't start. I then tried starting it while pressing the gas a bit (like in the old days) and it started. I drove back towards the house and it ran fine while at speed, engine felt really strong. Then got it in the driveway and it wont idle, just dies.

So any idea what would cause this ? Strange that it started perfectly when I first started the car but then after driving it I had the idle issues.

I thought it was a maybe a warm idle issue but I tried starting it cold this morning before work and it wouldn't idle, just like last night. I gave it some gas and it was able to start. I held my foot on the gas pedal slightly and I sat there idling but the moment I take my foot off the gas, it dies.

Any ideas ? not too happy right now with my 'new' car. :moping:

 

[narow37]

Sounds like the Idle Air Control Valve needs cleaned. same symptoms as mine last winter.

 

[Jason11]

Sounds like the Idle Air Control Valve needs cleaned. same symptoms as mine last winter.

Hey Narow -- Guess what? I took the throttle body off last night and did a thorough cleaning of everything (IAC and throttle body itself) I used the CRC throttle body cleaner. Got it all back together.


.... and the car started and runs perfect. Took it out down the street and no engine stall issue any more. Runs strong all the way to redline. The idle does seem a little high now on a cold start (not sure if that is normal on these 3.4L engines.)

Thank you for the suggestion, its fixed.

Just a note about the CRC TB cleaner; it doesn't seem as aggressive as brake cleaner. I had to really use lots of the TB cleaner and it was tough to get the carbon deposits off. I imagine if I used brake cleaner it would have come off easier.. not sure if brake cleaner would be safe for the throttle body.

 

[JayRolla]

Hey Narow -- Guess what? I took the throttle body off last night and did a thorough cleaning of everything (IAC and throttle body itself) I used the CRC throttle body cleaner. Got it all back together.


.... and the car started and runs perfect. Took it out down the street and no engine stall issue any more. Runs strong all the way to redline. The idle does seem a little high now on a cold start (not sure if that is normal on these 3.4L engines.)

Thank you for the suggestion, its fixed.

Just a note about the CRC TB cleaner; it doesn't seem as aggressive as brake cleaner. I had to really use lots of the TB cleaner and it was tough to get the carbon deposits off. I imagine if I used brake cleaner it would have come off easier.. not sure if brake cleaner would be safe for the throttle body.

High idle is normal on cold starts for these motors.

 

[Flatulento]

So I had the same high idle issue after cleaning the throttle body on mine. After some research in the forum, I found the link below and adjusted the throttle plate side-to-side spacing ever so slightly. It worked. Mine does still idle high (1400 - 1600 rpm) when cold, but slows down (800-900) once warm.


http://www.toyota-4runner.org/3rd-gen-t4rs/123396-my-high-idle-cured.html

 

[narow37]

Hey Narow -- Guess what? I took the throttle body off last night and did a thorough cleaning of everything (IAC and throttle body itself) I used the CRC throttle body cleaner. Got it all back together.


.... and the car started and runs perfect. Took it out down the street and no engine stall issue any more. Runs strong all the way to redline. The idle does seem a little high now on a cold start (not sure if that is normal on these 3.4L engines.)

Glad it worked out for you. As i said, mine was the same symptoms and the fix was as you said, night and day difference. I used TB cleaner and a bristle brush to help it along.
Cheers.

 

[19963.4lsr5]

So I had the same high idle issue after cleaning the throttle body on mine. After some research in the forum, I found the link below and adjusted the throttle plate side-to-side spacing ever so slightly. It worked. Mine does still idle high (1400 - 1600 rpm) when cold, but slows down (800-900) once warm.





http://www.toyota-4runner.org/3rd-gen-t4rs/123396-my-high-idle-cured.html

Have you looked for vacuum leaks? That seems high to me.

 

[Flatulento]

Yeah, I did check the vacuum lines and connections just to make sure. However, I can cause the idle speed to change just by pushing the throttle plate bolt in or out just slightly. I probably did not get the plate centered in the bore exactly right using the spacer method. I actually used a fat o-ring that fits just inside the recessed area where the throttle plate bolt enters into the throttle body. I'm okay with 800-900 rpm, so haven't bothered to adjust any further.
I have an inkling that the carbon build-up around the bore/throat, where the throttle plate sits at idle, actually blocks incoming air flow. Since I removed the build-up when cleaning, the effective gap around the throttle plate is greater, thus resulting in more air flow and higher idle.