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TPS wiring questions

I did pull it and clean it. I haven't applied voltage as I don't know how to apply voltage without getting the pin extended out too far.

I did swap it out with 2 other used IACVs and it didn't change the idling problem.
 
I went through already and tightened up the bolts holding the manifold onto the engine. A few of them turned about 1/4 of a turn pretty easy. That lowered the idle a little but did not produce any long-term effects. If the engine is idling really high, will the water/carb cleaner trick be noticeable?

I did splice a new ground onto the TPS harness for the TCU ground wire and that helped for a little bit but then the engine went crazy again.

I Don't hear any discernible vacuum leaks, either. I know when one of the vacuum hoses is unplugged I can hear the 'ssssssssss' sound it makes. I would think that if there was a vacuum leak, not only would I be able to hear it it would create a consistent crazy idling problem.
 
I'll crawl under there and make sure all the sensors are properly connected and not frayed. The CPS is brand new and the wires are not shorting on anything.

I already checked the manifold bolts except for the front two on the bottom because I couldn't reach them. I'll try to reach those again and make sure they are really tight; though none of the others were very loose.

I did the carb cleaner trick and nothing happened; probably because it was already idling at 11000 RPM. I'll try the water trick and spray it around all the joints and seals and see if it drops the idle.

I have a vacuum gauge; do you want me to take some readings or make a video of the idling+vacuum gauge?
 
Wouldn't hurt.
 
OK, so as far as I can tell, the bolts holding the intake manifold on are snug and tight.

However, when I tried to test the resistance of the coolant temp sensor, I couldn't get it to maintain a consistent reading. I tried to clip on two alligator clips, tried one alligator clip and one DMM probe, two DMM probes but nothing I did would allow me to maintain a steady reading on the CTS. The truck was not warm, though, so I don't know if that was a problem. I would assume that the sensor, if good, would still read a consistent resistance. The DMM gave me an "OL" reading.

Thoughts?
 
Last edited:
Ok, prepare a "Plug" to keep the coolant in, pull the CTS from the block and bench test it on the stove or with a hair dryer/heat gun.

Did you do the water test or just make sure the intake was tight? You can have a tight mounting but if the gasket is FUBAR there won't be a seal.
 
joe_peters said:
Ok, prepare a "Plug" to keep the coolant in, pull the CTS from the block and bench test it on the stove or with a hair dryer/heat gun.

Did you do the water test or just make sure the intake was tight? You can have a tight mounting but if the gasket is FUBAR there won't be a seal.
Click to expand...

Perhaps I'll just get a new CTS and bench test it before I install it then remove the old sensor. If the old sensor turns out to be good, I'll just remove the new sensor; otherwise, the new sensor is already in place.

I did not do the water test - I ran out of time last night. I will try to do that tonight. I sure hope the gasket is good - I don't feel like pulling the intake.
 
Sounds like a plan, get us updated.

EDIT: when you do the water, spray around the injectors where they enter the intake too.
 
Will do.

When I pull the old CTS out, I assume coolant will come pouring out pretty heavy, so I should be quick with the plug.
 
Update: I went out and sprayed down the intake/engine gasket area. I basically soaked it until there were pools of water sitting there and started the engine. There was no change in the idle and nothing discernible happened. I made sure to go back and spray it down while the engine was running.

I did not crawl under the truck while it was running, though.

My next step will be to replace the CTS with a new one (bench tested before installation) then bench test the old one. Perhaps this will alleviate the 'weed-eater' smell.
 
So I installed the new CTS in an HO thermostat housing. Tested the new CTS and it was showing about 300 ohms which is about correct.

The engine was still idling stupid high in P/N and in all the drive gears. I basically didn't even need to use the gas, as it accelerated itself and changed gears.

So the new CTS still hasn't changed the problem any or made it any better. What to do now?
 
I also hooked up a vacuum gauge and it hovered right around 23 (green zone on the gauge). The engine idle speed fluctuated somewhat but nothing significant. During this, the vacuum gauge barely moved.

CTS, MAP, MAT all checked out according to lunghd specs. Maybe it's a bad ground to the computer?
 
bigalpha said:
I also hooked up a vacuum gauge and it hovered right around 23 (green zone on the gauge). The engine idle speed fluctuated somewhat but nothing significant. During this, the vacuum gauge barely moved.

CTS, MAP, MAT all checked out according to lunghd specs. Maybe it's a bad ground to the computer?
Click to expand...

Damn!

I just can't get over that it can idle high other than the throttle plate being opened, busted IAC, OR an intake leak. We know the throttle plate is closed and set and you have been through the IAC.

Humor me, start pulling things off the intake manifold and plugging the ports--mark them if you think you might get them mixed up. It has got to be something--brake booster, MAP, vacuum harness, EVAP, something is allowing air into the system.
 
i had the same problem when setting my tps...after it was perfect at 83% of input voltage it idled at 3000 rpm everytime i started it....so i unhooked the battery and walked away for awhile before i burned it to the ground! needless to say when i hooked it back up it started up and purred like a kitten. not saying thats ur prob but it worked for me
 
joe_peters said:
Damn!

I just can't get over that it can idle high other than the throttle plate being opened, busted IAC, OR an intake leak. We know the throttle plate is closed and set and you have been through the IAC.
Click to expand...
I did swap the IAC with 3 used ones and not one of them made any difference. Maybe I should try a new IAC just for shits and giggles.

Humor me, start pulling things off the intake manifold and plugging the ports--mark them if you think you might get them mixed up. It has got to be something--brake booster, MAP, vacuum harness, EVAP, something is allowing air into the system.
Click to expand...

So you basically want me to isolate some of the components that use vacuum to make sure that one of those components isn't allowing a ton of air into the engine? Sounds straightforward enough.

90 waggy said:
i had the same problem when setting my tps...after it was perfect at 83% of input voltage it idled at 3000 rpm everytime i started it....so i unhooked the battery and walked away for awhile before i burned it to the ground! needless to say when i hooked it back up it started up and purred like a kitten. not saying thats ur prob but it worked for me
Click to expand...

I'll try this too, just to rule out something weird with the battery and computers. It idled really high before, then I ran a new ground from the TCU connector on the TPS and it basically cured the insane idle; then the insane idle came back.

Thanks for all the help and suggestions everyone! I'm determined to get this baby running nicely.
 
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