2001 - Silverado 2500 - high RPM

[fear_nothing]

2001 / 6.0 / Chevrolet silverado 2500 / 5-speed manual.

Will a faulty throttle position sensor cause the throttle to almost run away?

Its been idling high for a couple months. Had it on the highway today and it was a little rowdy. Had to shut it down at the stop lights as it was too much for the clutch to hold. It was slipping and start to smoke.

I've got a new sensor ordered. I'll report back on the codes its throwing.

Anything else I should be checking?

Much obliged.

 

[eric67camino]

Intake leaks may cause a high idle, but I doubt that high.

I believe there is a resistance test procedure to check and verify that the tps is out of spec. You may check that before replacing the part.

 

[Blue85]

It would be setting lean codes before an intake leak got that bad. This is throttle by wire with separate throttle motor and tps connectors, right? Have you checked/cleaned the throttle body? It could also be a problem with the pedal sensor or the throttle controller box. If you have a simple scanner, see what it's reading for %throttle. Of course read the fuel trims while you're in there.

 

[fear_nothing]

Intake leaks may cause a high idle, but I doubt that high.

I believe there is a resistance test procedure to check and verify that the tps is out of spec. You may check that before replacing the part.

Much obliged - All things considered....Prob wont spend much time troubleshooting when Gray Santa [amazon] will deliver the 20 dollar part by this afternoon. I would presume it will be monumentally easier to install than the #$&#$*#%^*%^* power steering pump that was installed about a month ago.

 

[ZooMad75]

2001 6.0 most likely is still using a cable throttle. So that limits some reasons that it would go high throttle. The cable would have to be hanging up.

A throttle position sensor wouldn’t be a direct cause of excessive idle on its own. It would be setting codes for sure and causing the check engine light to come on.

The main culprit in my mind is the IAC or idle air control motor. The motor just drives a pintle in and out to essentially be a controlled leak letting air bypass the throttle blade. The motor can act up or stick and another issue is a vacuum leak past the o-ring that seals it.

I’ve had this act up on my 8.1 which has a cable throttle set up similar to a 6.0 on an early gmt800 truck. The idle was inconsistent. Come to a stop and the idle would be as high as 2500 RPM and then the next time I stopped it would be at 500 RPM. But having a manual trans made it a bit challenging as some times it was high enough it felt like I was launching it at the drag strip. The centerforce clutch was able to hold it though.

Those are fairly inexpensive too.

 

[Blue85]

I've seen the DBW throttle on 2001 trucks. I think at least some had it in 2000. It's in 03 they switched to the combined motor/sensor in one package. But my experience is with SUVs, the pickups kept the cable longer.

 

[ZooMad75]

I've seen the DBW throttle on 2001 trucks. I think at least some had it in 2000. It's in 03 they switched to the combined motor/sensor in one package. But my experience is with SUVs, the pickups kept the cable longer.

I agree some did get DBW throttles. But the earlier you go the more likely a truck would have the cable throttle. I think the 6.0’s in the 1500hd’s, 2500 LD and 2500hd’s kept the cable longer than the 4.8/5.3’s did.

 

[Blue85]

I agree some did get DBW throttles. But the earlier you go the more likely a truck would have the cable throttle. I think the 6.0’s in the 1500hd’s, 2500 LD and 2500hd’s kept the cable longer than the 4.8/5.3’s did.

Yeah, sounds about right. An easier way would be if @fear_nothing just told us or sent pics.

 

[fear_nothing]

Yeah, sounds about right. An easier way would be if @fear_nothing just told us or sent pics.

fear has a day job

 

[fear_nothing]

Replaced the TPS - no effect it still idles super high at roughly 4000 RPM.
It is DBW - as seen here. someone will ask - no I didn't add the spacer block

 

[fear_nothing]

Here the the codes, the MAF one look generic - I can replace if y'all think that will help

 

[fear_nothing]

Lastly - here is the full read out from the scanner. Thanks!

 

[fear_nothing]

It would be setting lean codes before an intake leak got that bad. This is throttle by wire with separate throttle motor and tps connectors, right? Have you checked/cleaned the throttle body? It could also be a problem with the pedal sensor or the throttle controller box. If you have a simple scanner, see what it's reading for %throttle. Of course read the fuel trims while you're in there.

throttle body is clean, checked w/ a white rag - no build up or obstructions noted. I posted the full read out from the scanner - is that what you meant in relation to the fuel trims?

 

[fear_nothing]

throttle body is clean, checked w/ a white rag - no build up or obstructions noted.

2001 6.0 most likely is still using a cable throttle. So that limits some reasons that it would go high throttle. The cable would have to be hanging up.

A throttle position sensor wouldn’t be a direct cause of excessive idle on its own. It would be setting codes for sure and causing the check engine light to come on.

The main culprit in my mind is the IAC or idle air control motor. The motor just drives a pintle in and out to essentially be a controlled leak letting air bypass the throttle blade. The motor can act up or stick and another issue is a vacuum leak past the o-ring that seals it.

I’ve had this act up on my 8.1 which has a cable throttle set up similar to a 6.0 on an early gmt800 truck. The idle was inconsistent. Come to a stop and the idle would be as high as 2500 RPM and then the next time I stopped it would be at 500 RPM. But having a manual trans made it a bit challenging as some times it was high enough it felt like I was launching it at the drag strip. The centerforce clutch was able to hold it though.

Those are fairly inexpensive too.

This one work? https://www.amazon.com/ACDelco-1711...&vehicleName=2001+Chevrolet+Silverado+2500+HD

 

[eric67camino]

Lastly - here is the full read out from the scanner. Thanks!
View attachment 403087

I'm concerned that the IAT (intake air temperature) looks the be negative 38.2 degrees.

I think the engine may be seeing that, thinking that the air is colder than it is, and adding fuel. Kinda like the choke being on when it's cold with a carburetor.

 

[eric67camino]

Replaced the TPS - no effect it still idles super high at roughly 4000 RPM.
It is DBW - as seen here. someone will ask - no I didn't add the spacer block

View attachment 403085

That's not DBW. That's the cable system.

One cable for the throttle control.
One cable for the cruise control motor.

Drive by wire uses a sensor at the foot pedal and an electric actuator at the throttle body. No physical cable moving it.

 

[fear_nothing]

That's not DBW. That's the cable system.

One cable for the throttle control.
One cable for the cruise control motor.

Drive by wire uses a sensor at the foot pedal and an electric actuator at the throttle body. No physical cable moving it.

Well damn... this guy learned something today

 

[ZooMad75]

This one work? https://www.amazon.com/ACDelco-17113598-Original-Equipment-Injection/dp/B000C9IXUI/ref=sr_1_2?crid=39PNVCO7I01T6&keywords=idle+air+control+motor&pd_rd_r=18669cb1-b571-44a6-b377-5e54bcb93127&pd_rd_w=eLPQL&pd_rd_wg=foLvb&pf_rd_p=ce8592e7-3f5d-4c47-8fd0-5053ffa3307b&pf_rd_r=6GRQERJYXF5304WEM3EN&pid=1lsPWtx&qid=1645056105&sprefix=idle+air+control+motor.+,aps,427&sr=1-2&vehicle=2001-47-494-96-29-31-6-8-22188---2-1105--&vehicleName=2001+Chevrolet+Silverado+2500+HD

Yep that’s the one.

I'm concerned that the IAT (intake air temperature) looks the be negative 38.2 degrees.

I think the engine may be seeing that, thinking that the air is colder thann it is, and adding fuel. Kinda like the choke being on when it's cold with a carburetor.

The system looks at IAT and coolant temp to know if the engine is up to temp or not. Not specifically looking at the IAT alone but it can bump idle speed based on coolant temperature. It will not bump it much over normal.

Typical GM temp senders are high resistance at low temps and low resistance at high temps. Don’t matter if it’s the IAT, coolant temp or even the ambient temp sensor. Because of that when you see an insanely low temp like -30 or below you need to look for an open circuit on the signal wire back to the pcm. If the circuit is good you can condemn the sensor. Could be a chewed wire or it got unplugged during the p/s pump job and never plugged back in. On that truck the IAT is separate from the MAF.

The knock sensor code you have isn’t a cause for the rpm swing but it will be cutting power/timing if it incorrectly senses knock. Chances are the knock sensors are original to the truck. And given the rusty fight you had getting the pump off I’d bet the two knock sensors look like they have been at the bottom of the ocean with the Titanic.

That repair will need two knock sensors, the knock sensor harness (I’ll explain) and a pair of intake gaskets. The harness has two rubber plugs that seal off the holes so water does not collect in the cavities where the sensors are. They get old and stuff and don’t seal after a while. They won’t seal up if you try to reuse it. With the new plugs on the new harness gm came back to recommend to add rtv sealant around the edge of the plug and a dollop where the wire goes through it.

That repair is not hyper critical. It does not have to be done right away. But put it on your radar.

 

[Blue85]

I don't know where you are in "USA", but unless it's Northern Alaska, it's probably not -38F, so you have a broken wire or bad sensor as ZooMad said. About half of the numbers on the scanner are meaningless because the engine isn't running. The fuel trims and throttle % while it's at the high idle are most helpful (fuel trims are not single numbers, but tables. The values displayed correspond to the current engine load and speed conditions.)

 

[fear_nothing]

Lol its def not -38 in the South. The Fuel Injection Idle Air Control Valve gets replaced sometime tomorrow or this weekend.