High idle @ 2k

[VirtuaDude]

I have a 2000 4runner. Replaced the following:

muffler
hoses
spark plugs
fuel pump
fuel filter
maf sensor
oil for trans, transfer case, and rear
throtte pos sensor
oil cooler gaskets
Fuel inject rebuild kit
New chinese thorttle body w/ TPS and IAC

My truck sits over 2k RPM at idle. Putting a spring on on of the "cam pulleys??" as seen in photos brings the idle down to 1400 RPM. It did this with the old throttle body too. Thought the new one would fix it. Mechanic already did a scanner commanded "throttle relearn". No lock here. It just stays high until you are driving it at speed and in gear. Then it runs normal. When you slow down to a stop, the idle is high again. When going over 30 MPH, if you put it in Nuetral, it will surge up and down between 1100 and 2k RPM. Please help.

 

[VirtuaDude]

I have a 2000 4runner. Replaced the following:

muffler
hoses
spark plugs
fuel pump
fuel filter
maf sensor
oil for trans, transfer case, and rear
throtte pos sensor
oil cooler gaskets
Fuel inject rebuild kit
New chinese thorttle body w/ TPS and IAC

My truck sits over 2k RPM at idle. Putting a spring on on of the "cam pulleys??" as seen in photos brings the idle down to 1400 RPM. It did this with the old throttle body too. Thought the new one would fix it. Mechanic already did a scanner commanded "throttle relearn". No lock here. It just stays high until you are driving it at speed and in gear. Then it runs normal. When you slow down to a stop, the idle is high again. When going over 30 MPH, if you put it in Nuetral, it will surge up and down between 1100 and 2k RPM. Please help.

Temp sensor too.

 

[1blink]

Have you tested for vacuum hose leaks?

 

[VirtuaDude]

Have you tested for vacuum hose leaks?

My mechanic did a smoke test on it and was not able to find a leak. I'm about to disconnect most of the lines and see if I can make it behave more.

 

[phattyduck]

When going over 30 MPH, if you put it in Nuetral, it will surge up and down between 1100 and 2k RPM. Please help.

Based on the 'missing' trans cable, I'm assuming you have a manual transmission?

This 1100-2000 RPM oscillation is because at speed, the ECU will do fuel cut when your foot is off the throttle and the RPMs are above ~1100-1200 RPM. When it gets down there, it puts fuel back - and your engine is pulling in enough air to 'idle' at 2k RPM - so that's the fuel it gives and it revs back up - then the process repeats.

You need to figure out why there is extra air getting into the engine. Throttle body gasket backwards? Hoses swapped? Throttle cables too tight? Etc...

-Charlie

 

[VirtuaDude]

Based on the 'missing' trans cable, I'm assuming you have a manual transmission?

This 1100-2000 RPM oscillation is because at speed, the ECU will do fuel cut when your foot is off the throttle and the RPMs are above ~1100-1200 RPM. When it gets down there, it puts fuel back - and your engine is pulling in enough air to 'idle' at 2k RPM - so that's the fuel it gives and it revs back up - then the process repeats.

You need to figure out why there is extra air getting into the engine. Throttle body gasket backwards? Hoses swapped? Throttle cables too tight? Etc...

-Charlie

Thank you good sir! I will start isolating the vacuum system. Just replaced the throttle body gasket and it can only go in one way as it was a metal gasket with imprint. If there is any vacuum leak coming from the hoses, it will be the ones that are on the fender well and go down under the vehicle. I replaced nearly all others already.

 

[phattyduck]

There will be one small hose down to the vacuum canister in the front of the driver's wheel well... Does 4WD engage correctly? Otherwise, if you have a leak in the vent hose for evap, you'd be getting a CEL for that...

I'm suspecting a swapped vacuum hose or something like that... Make sure you track each one and understand exactly what each hose does. Post photos of anything you have questions about.

-Charlie

 

[Spiker Engineering]

Can you tell us more about the Chinese IAC?

 

[BuffaloBass]

If CHarlie's vacuum diagnostics dont cure it, the Chi-com iAC is what i suspect. Test it. I know there is a test as i tested mine when i rebuilt the TB.

PS my booster failed after sitting, and yes that will throw a code and make idle high. If you have no codes however, i suspect the IAC is compromised.