2.9 high idle continues to rev

[Sicktight722]

hey. I have a 1990 bronco II 4x4 with the 2.9L and a 5spd. The idle seems a little high, but it could also be the rpm gauge. My main concern is when I am driving, when I press the clutch to shift gears or when I put it in neutral to come to a stop the engine revs really high. Most of the time its 1000 rpm higher than when I press the clutch in. I have put on new spark plug wires, regapped the spark plugs, replaced the IAC and tested the TPS (which was .92 at closed and 4.86 at full throttle. I have also checked the vacuum buy spraying ether on the hoses and intake and nothing changes. What else can I do to stop this? I did run a 1/3 can of seafoam thru it and it started with the over reving. The high idle has been with the truck since I've had it. I'm thinking about unplugging the O2 sensor but I can't seem to find where it plugs in at. what do yall suggest. The over reving is killing my mpg

 

[Jspafford]

Check the Fuel pressure regulator to see if it is leaking into the vacuum tube.

Could be flooding out the engine.

 

[BlackBII]

If the motor is revving up, then Air has to be getting in somehow.

Air enters the motor by
IAC - You replaced it
Vaccum leaks - I assume you've checked for these
Throttle Body

I've had many a RBV rev high because the throttle linkage was gettign stuck, keeping the throttle plate open. There is a plastic sleeve that the cable runs into near the throttle body, I've had the cable get stuck on this sleeve

My bet is that when you let off the pedal, the throttle plate isnt closing all the way

 

[Sicktight722]

If the motor is revving up, then Air has to be getting in somehow.

Air enters the motor by
IAC - You replaced it
Vaccum leaks - I assume you've checked for these
Throttle Body

I've had many a RBV rev high because the throttle linkage was gettign stuck, keeping the throttle plate open. There is a plastic sleeve that the cable runs into near the throttle body, I've had the cable get stuck on this sleeve

My bet is that when you let off the pedal, the throttle plate isnt closing all the way

I checked the vacuum leaks with a can of ether. no change in the rpms when I sprayed. I will check the throttle linkage though.

Check the Fuel pressure regulator to see if it is leaking into the vacuum tube.

Could be flooding out the engine.

where is the fuel pressure regulator and how do I check it?



**I should also add that it does not stay revved up, it only does it for about 4 or 5 seconds then it goes back down to where it should be

 

[sjr53]

For lack of a better idea, how about disconnecting the battery for a few minutes to do a reboot on the EEC. Works wonders on a PC.

 

[Jspafford]

FPR is located close to the back of the driver side valve cover. Round cylinder with two fuel lines and one vacuum line coming off it.

Might also check the CTS (Coolant Temp Sensor) is within spec... Although, that usually results in a hard to start condition upon warm starts.

 

[Sicktight722]

FPR is located close to the back of the driver side valve cover. Round cylinder with two fuel lines and one vacuum line coming off it.

Might also check the CTS (Coolant Temp Sensor) is within spec... Although, that usually results in a hard to start condition upon warm starts.

checked the FPR by pulling the hose that goes to it from the intake off, and no gas dribbled out. I also checked the CTS and the resistance was in spec to a chart on the autozone website. I adjusted my TPS sensor down to ~.70 instead of the ~.92. Now it idles fine and does not rev up but it is hard to keep idling untill it gets warm. I guess I have to find the sweet spot for the TPS

 

[kurama49]

checked the FPR by pulling the hose that goes to it from the intake off, and no gas dribbled out. I also checked the CTS and the resistance was in spec to a chart on the autozone website. I adjusted my TPS sensor down to ~.70 instead of the ~.92. Now it idles fine and does not rev up but it is hard to keep idling untill it gets warm. I guess I have to find the sweet spot for the TPS

Hey im having the same problem. Could you mabey tell me what tps means and where it is on my 2.9?

 

[Big Jim M]

Throttle Position Sensor= TPS. It's job is to tell the computer how wide open the throttle body is so the computer can adjust the amount of fuel deployed.
It is right there on the opening valve of the throttle body.
Big JIm

 

[RustedRanger]

Try taking a rag soaked with throttle body cleaner and clean the back of the throttle plate. A friend told me to do this even though I had already spayed a can of cleaner through the intake. There must have been a 16th of an inch of black crud on the backside of the throttle plate. This can cause hard to diagnose problems.

 

[Duane867]

Be REAL careful spraying cleaners in a 2.9L.
They have poor oiling designs from the factory and you can easily clog up the return or injection oil ports in the heads. You do this and you can hang it up. The heads will fry in a heart beat.

 

[glendtcocaine]

I had the same problem nagging me for a month. I bought a new throttle cable and popped it on and over revving completely stopped!