Hi,

I'm new to the forum and there is nothing like starting out with problem for your first post. My 1991 Regal Custom has a very high high idle, like I can get up to 40 MPH without engaging the accelerator pedal. This performance is as of last night when I changed out the TPS. The problem I had before this was it would NOT idle for 90 - 120 seconds. I had to feather the accellerator for up to two minutes and then it would idle - a little high but not bad. I had changed out the IAC and MAP about 500 miles ago. Back then it would stall out a not. Oh, I also, swapped the vacuum hoses.

The engine is a 3100 with MPFI.

When I changed out the TPS, it is nesltled under the IAC in the front of the throttle body. I thought you didn't need to adjust the TPS when you installed it -- was I wrong? The codes yesterday were 23, 35 and 44. All those codes went away and now it is throwing a 33 which is high voltage from MAP and/or MAF. I'm thinking the MAP is OK, but I can't vouch for the MAF.

I'm open to suggestions now, because before I changed out the TPS, idle was basically fine and acceleration was very smooth. To get at the TPS you have to remove the IAC and unbolt the throttle body and pull it back just a little bit to get the torx bit on the but screw. It wasn't difficult, but wow did I get a change in idele performance - real high. Acceleration is still smooth, runs real nicebetween 70 - 90 MPH on the Interstate.

Thanks in advance!

Steve

It sounds to me as if you have a vacuum leak, possibly in the line supplying the MAP sensor. It runs under the upper plenum, and will be a major vacuum leak, which would cause your high idle and the trouble codes you have.

It sounds to me as if you have a vacuum leak, possibly in the line supplying the MAP sensor. It runs under the upper plenum, and will be a major vacuum leak, which would cause your high idle and the trouble codes you have.

Thanks for the reply and I believe you are right. The other day I took the throttle body off and the upper right mounting bolt hole tab was cracked - it fell off into my hand. That could be a problem, sucking in air and making the MAP go crazy. Definitely would account for the code 33. The broken piece is am integral part of th eupper intake manifold. GM wants $339.00 dollars for an upper intake manaifold, so, being a huge believer in JB Weld; I fixed it and used RTV 28 to make a gasket on the throttle body to intake manaifold connection. This afternoon around 5:00pm I'll know if my repair is good.

In being a firm believer of JB Weld, I also am a firm believer in following their instructions; let the product cure for 24 hours before putting the part into use.

Tomorrow I'll let you know if the repair is good.

Thanks for the reply and I believe you are right. The other day I took the throttle body off and the upper right mounting bolt hole tab was cracked - it fell off into my hand. That could be a problem, sucking in air and making the MAP go crazy. Definitely would account for the code 33. The broken piece is am integral part of th eupper intake manifold. GM wants $339.00 dollars for an upper intake manaifold, so, being a huge believer in JB Weld; I fixed it and used RTV 28 to make a gasket on the throttle body to intake manaifold connection. This afternoon around 5:00pm I'll know if my repair is good.

In being a firm believer of JB Weld, I also am a firm believer in following their instructions; let the product cure for 24 hours before putting the part into use.

Tomorrow I'll let you know if the repair is good.

It is better but I was not able to totally seal up the interface of the throttle body to the upper intake manifold. So, this weekend I will look for a upper intake manifold and just replace it, replace all the gaskets and that should be it.

The 'high' idle I had before was actually run away accelleration to WOT, but now it is just a hgh idle that will sustain about 34 MPH on level grade. The other day I could sustain around 72 MPH on level grade -- not a good thing.

GM wants to much for their upper intake manifold ($339.00 USD), anybody know where I can get a used one for under a benjamin?

It is better but I was not able to totally seal up the interface of the throttle body to the upper intake manifold. So, this weekend I will look for a upper intake manifold and just replace it, replace all the gaskets and that should be it.

The 'high' idle I had before was actually run away accelleration to WOT, but now it is just a hgh idle that will sustain about 34 MPH on level grade. The other day I could sustain around 72 MPH on level grade -- not a good thing.

GM wants to much for their upper intake manifold ($339.00 USD), anybody know where I can get a used one for under a benjamin?

For those that are interested, his is now a closed item. The replacement of the TPS and installin a new gasket onto the throttle body has returned this vehicle to normal operation. I still need to get a new upper intake manaifold, however, the JB Weld job is holding up well.

Now, I need to open another help request because when I went for my last test drive the right rear forward lateral stabilizer bar snapped into which causes the wheel to angle out by about 20 degrees. Stuff never ends does it.