2000rpm idle

[Bocephus]

I'm new to the forum and just picked up a 95 k1500 sportside with the 350 in it. Had it about a week and all of a sudden idle jumps to 2000rpm and hasn't come down since. The TPS sensor and the IAC valve both seem to be in working order ( checked both with multi meter ). Sprayed starter fluid around every vacuum leak spot I could find and rpms stayed the same. The previous owner converted it from a automatic to a 5spd and didn't change the ECM and I'm showing a TPS low signal code ( has correct volts but changed anyway with no change in rpm). What are the chances it's the ECM vs throttle body. Also before the check engine light came on I had to jump a car off, done it a million times in many vehicles,where no sparks or prolonged connection between the truck and car with dead battery. Is there a chance it screwed the ECM ? Any help would be greatly appreciated

 

[BOOT]

Sounds like a possible vac leak to me, I've never liked the spray all around method. How are the brakes, did you test the booster or check the hose? Does the TB linkage/cable move freely? Any weird floor matts?

 

[Bocephus]

Brakes work good. With the Key off brakes build and hold pressure after 2 pumps so the booster is fine, hose looks fine to and didn't respond to starter fluid either. I'm not sure what you mean about weird floor mats though

 

[Schurkey]

Connect a scan tool, let the computer tell you what's wrong via the data stream.

Pinching off vacuum hoses isn't a bad plan. See what happens.

Make sure the transmission TV cable, the cruise control cable, and the throttle cable aren't holding the throttle open. Especially important since you're getting a TPS code.

 

[Bocephus]

Cables ain't holding it open it don't look like,before the code and the high idle showed up it would sometimes hang a little bit while out and about but tapping the gas lowered It back down. I guess I could disconnect the cables all together from the linkage just to be sure. I don't have a scan tool that will work for OBD1, I retrieved the codes with the paper clip method

 

[Bocephus]

So the throttle cables ain't the issue and I pulled the throttle body off and cleaned it up with all new gaskets still high idle. Pulled the TPS sensor connector off and the idle drops ,connect it back and it increases, push the TPS lever all the way up like it's wide open throttle and rpm goes back down. The throttle body is a 88-89 and the truck is a 95. Only thing I can figure is it's not reading it right cause I've replaced it with no change and checked with a voltmeter and it checked out fine. Please help

 

[Bocephus]

I didn't put the throttle body on, it was like that when I bought it and drove fine for almost a week before the high idle started. Has a new IAC valve and the IAC idle relearn does not lower idle at all.

 

[udidwht]

Have you given the idle adjustment screw a shot? The sealed one.

 

[Griffin Meeks]

Low signal may be a power/ground issue. What do the connectors to the TPS look like?

The code might also be a red herring. I had some trouble with high idle a couple years ago, and it ended up being related to the MAP sensor.

Either way, both the MAP and the TPS work together to tell the ECU engine load. If one of the signals goes out, then most systems default to a preset rpm as a sort of "best guess" to keep you from getting stranded. It sounds like that might be what's happening here, so I'd focus on eliminating all possible electrical faults as the first step.