New TPS= High Idle ?

[DuallyGuy]

I've been doing a lot on my truck lately to get her ready for a little trip up the coast. I had the radiator pulled, new thermostat, new wires, plugs, new fuel injector connectors, etc. I also replaced the TPS and it's connector due to a small engine fire which melted the old TPS and connector together. Although the truck still ran fine, it looked tacky and figured it was best to replace it to prevent complications. Well now that I've replaced the TPS and connector, my truck idles too high. I tried adjusting the TPS by loosening the screws and adjusting the position of it against the TB, but it still idles way too high. I'm going crazy trying to find posts on the internet to explain what happened. Any info would be greatly appreciated. Thanks in advance.

 

[crazy4offroad]

Last time I messed with fuel injection, adjusting the TPS involved using feeler gauges and an ohm meter, it wasn't something you could just tune by ear. You may want to pick up a cheapie Haynes manual at the parts store for the proper procedure.

 

[89Suburban]

I think Jim talked about a procedure for setting that, let me see if I can dig it up...

 

[Jims86]

Hey Matt,
Idle re learn is not usually needed, but try it anyways.
Check to make sure you wired the new plug right, and you didnt knock any vacuum lines off.
If you have A digital volt meter, (with the key on)probe the dark blue wire on the TPS plug, with the positive, and probe the black tps wire with the ground, and make sure the voltage is under 1 volt. If you have the adjustable TPS, set it to .54v, otherwise, I have seen as high as .70 from the factory
with a paper clip, jump A and B on the diagnostic connector, and turn the key on for 30 seconds. Take the paper clip out.
Disconnect the battery for 15 seconds, re connect it.
Now start the engine, ifvthe idle is good, drive around for about 1/2 hour and let it re learn the idle. cold start should be no more than 1200 rpm.
Too bad you are over 300 miles away, I would hook it up to my laptop.

 

[DuallyGuy]

Thank you for all the great input. I do have a multimeter, but i have no clue how to set the TPS to.54 though. Never done it before.

 

[Jims86]

Thank you for all the great input. I do have a multimeter, but i have no clue how to set the TPS to.54 though. Never done it before.

You can turn it a little either way. Some come with Oblonged holes for more adjustment. I usually oval them out with a drill. With the key on, and the probes on the before mentiond TPS wires, and the meter set to 20 volts, you can see what the voltage is. Wide open, the voltage should be around 4 volts, closed, should be no more than .70
.54 is best for idle.
If you oval out the holes, re install the TPS, but just snug the screws down so you can rotate the sensor with some resistance so it stays set. Kinda like a distributor when setting timing. Rotate the sensor clockwise to increase voltage, counter clockwise to reduce. If you can, take the air cleaner off, and post a video of what the engine is doing, that will also allow us to see anything you may be missing.

 

[DuallyGuy]

Ok. In that case, i did adjust the tps then. I have the tps at full tilt counter clockwise. The lowest reading I got was about 1.15. Is it just a cheap tps or something? Perhaps they sold me the wrong one?

 

[Jims86]

Ok. In that case, i did adjust the tps then. I have the tps at full tilt counter clockwise. The lowest reading I got was about 1.15. Is it just a cheap tps or something? Perhaps they sold me the wrong one?

Wow! did the prog get bent maybe? There is a prong from the sensor arm that rides on the throttle arm...make sure that is purpendicular to the path of throttle rotation...thats way too high. high sensor voltage will increase fuel delivery, and open th IAC Valve to achieve what that voltage commands.
Take the sensor off, leave it plugged in, and see what it idles at.

 

[DuallyGuy]

Im gonna try that soon as i get home. Although the tps fits right and snaps into the connector right, im starting to think they sold me the wrong one. But I'm gonna follow all these others steps as well if all else fails. Thanks for all your help.

 

[Jims86]

Im gonna try that soon as i get home. Although the tps fits right and snaps into the connector right, im starting to think they sold me the wrong one. But I'm gonna follow all these others steps as well if all else fails. Thanks for all your help.

All gm tps's are the same voltage wise, it is possible you got a bad one.

 

[DuallyGuy]

(sigh) Ok...Here is an update to my problem. I did everything that Jim mentioned. Paperclip on A and B, re-adjusted TPS, I even found one loose vacuum line. The TPS is basically screwed in with only one screw since that's the only way to dial the TPS down to it's lowest point. But the lowest reading I was able to get on my multimeter was .99v. I took the truck on a nice long journey up and down the highway and still as I pulled into the driveway and put it in park, she was still idling way too high. (what a waste of gas) Even with the TPS unmounted, I still get a high idle. So is it just a bad TPS? I mean it was only 45 bucks. It's a Standard Brand TPS. It was the only one available from the AC Delco warehouse. I've contacted 2 parts stores including the dealer. They're asking $148 for the TPS. So what gives? Why such a wide range in price? I also feel compelled to mention I installed a 185 degree thermostat since I plan on hauling a camper. That wouldn't have anything to do with it, would it? I'm pretty much at my ropes end here. Thanks again for the great advice though. I'd still be at square one had it not been for you fellas. Or I'd be handing some mechanic a blank check.

 

[Jims86]

(sigh) Ok...Here is an update to my problem. I did everything that Jim mentioned. Paperclip on A and B, re-adjusted TPS, I even found one loose vacuum line. The TPS is basically screwed in with only one screw since that's the only way to dial the TPS down to it's lowest point. But the lowest reading I was able to get on my multimeter was .99v. I took the truck on a nice long journey up and down the highway and still as I pulled into the driveway and put it in park, she was still idling way too high. (what a waste of gas) Even with the TPS unmounted, I still get a high idle. So is it just a bad TPS? I mean it was only 45 bucks. It's a Standard Brand TPS. It was the only one available from the AC Delco warehouse. I've contacted 2 parts stores including the dealer. They're asking $148 for the TPS. So what gives? Why such a wide range in price? I also feel compelled to mention I installed a 185 degree thermostat since I plan on hauling a camper. That wouldn't have anything to do with it, would it? I'm pretty much at my ropes end here. Thanks again for the great advice though. I'd still be at square one had it not been for you fellas. Or I'd be handing some mechanic a blank check.

Ok, That voltage is still way too high. Is the throttle closing all the way against the stop screw on the drivers side? The 185 thermostat needs to go, and the 195 needs to go back in. Any cooling system upgrades need to be confined to a bigger radiator when dealing with EFI.
Its harder for the engine to get into closed loop operation.
PM me your mailing info, and I will send you a TPS that I have modified to be adjustable, and I know for a fact that it goes all the way down to .49v.....maybe even a little lower.

 

[Jims86]

Also, one more thing to do. Go out and ground a and b again, turn the key on, and grab a flash light, pop the air cleaner and adaptor off, and look down into the Idle air passage, and after 30 seconds, or even before, you should be able to see the pintle tip in the passage, closing the idle air port. If not, thats a contributing factor to the high idle. And, If you have a timing light, make sure your timing is set at 4 degrees before top dead center.

 

[jt1200r]

check your idle air control valve. its the big sensor on the right side rear on the throttle body

 

[Jims86]

You want to look down in the IAC Passage.

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and you want to see the tip of the IAC pintle after 30 seconds.

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