After about week I noticed the truck was shifting differently, kinda like how it did when I had the transmission replaced. I took back to the them and they said the transmission is fine and its the throttle position sensor.

Now a week before this started to happen I replaced the TPS and MAP Sensor and a few days ago I replaced the EGR Valve.

Today I replaced the ICV, still no difference.

What else should I look for? I will replace the TPS again just to rule out a bum TPS.

1999 Blazer

 

If you're getting DTC's, and following the flow chart instructs you to replace a part, fine. If you're not getting DTC's, the sensors are operating within spec, and replacing them only wastes time and money. High idle is usually caused by binding throttle cable, throttle linkage, someone messing with the throttle stop screw, etc, or a vacuum leak such as an intake plenum gasket, throttle body gasket, faulty PCV valve, leaky brake booster, etc.

 

I'm curious if you have some gummed up residue around the throttle body blade, keeping it from closing properly.

Super easy to check, and good maintenance anyways, pop the air intake off the throttle body and check it's movement. buy some throttle body cleaner and spray it in and around there. Recheck the movement of the blade.

I would put the previous idle control valve back in since changing it didn't make a difference, if you still have it - and continue from there.

 

Looks like the throttle position sensor was bad, it had a crack inside. So what I think happened was....when I took it to the transmission place, there was a small crack in it, as I drove it and with the cold weather and hot engine, the sensor cracked more and more to where it cracked 100%. Truck started right up with the new sensor.

Soon as I took off the sensor and look inside I knew something was off.

Here are pics, old and new side by side and the old with a good view of the crack.

Now on to replace a leaky oil cooler line, O2 Sensor and then figure out the transfer case leak, hoping to find out why its stuck in 4 wheel.

 

That's what happens when the sensor is not lined up with the throttle shaft, and the sensor gets tightened down. Woops.

 

You think this was operator error? I hope I did it right this time

 

It should slide over the shaft very easily. Then hold it in place with your finger and install the screws. It needs to set flush against the throttle body before you tighten it up.

EDIT: If the sensor was jammed, it could very easily cause the idle to be high.

 

That's exactly what I did, I didn't install it the first time, buddy did it, since it was in his garage he went ahead and installed it.

Would have been faster if the radiator hose wasn't so close to it.

Question, the PCV valve "fell" out of the valve cover, isn't there supposed to be a grommet holding it in place? It's basically just laying inside the valve cover.

Truck drives crazy smooth now, this is the best its felt since I bought it.

 

Yes, there should be a rubber grommet in the rocker arm cover. Might have to go to the dealer, aftermarket ones don't always fit very well.