Reposting from wrong group. New to group, but searching for answers

[tbgrey2007]

2007 Chevy Tahoe developed an intermittent engine/tranny problem. The vehicle cranks and idles fine, but does not seem to respond to the throttle, rpms will not climb and vehicle lurches, like the throttle response is really delayed and limited. Local shop changed the throttle body and it ran fine. I picked it up and did not make it a 1/4 mile before it started again. Took it back and ended up putting in a remanufactured transmission. Vehicle has 230k so I figured that was coming. Picked it up, drove about 10 miles home, no problem. It sat for a day or two. I went to drive it and the same problem started again. Had the vehicle towed back to the shop and it ran fine on a test drive. Mechanic took it home and the next morning the problem started again (at least they see I'm not making it up). I checked the V4-V8 mode while it was misbehaving and it was show in V8 mode, so I don't think it is the AFM acting up. Shop has been looking at it for several days and seems to be stumped. Had a motor mount changed several weeks ago. Wondering if something could have gotten pinched during that process (wiring or a fuel line). Throttle position sensor checks out. I asked them to check the fuel pump and catalytic converter (maybe it is clogged up). No idea where to go from here. Thanks.

 

[Joseph Garcia]

Welcome to the Forum from NH.

Lots of knowledgeable folks here who freely share their knowledge, experiences, and perspectives. Knowledge is power.

I hope that you will become a participating member in the Forum's discussions.

Pics of the truck, please.

I cannot personally help you with your question; however, other members on this Forum that are much more knowledgeable than me will chime in.

 

[Doubeleive]

2007 Chevy Tahoe developed an intermittent engine/tranny problem. The vehicle cranks and idles fine, but does not seem to respond to the throttle, rpms will not climb and vehicle lurches, like the throttle response is really delayed and limited. Local shop changed the throttle body and it ran fine. I picked it up and did not make it a 1/4 mile before it started again. Took it back and ended up putting in a remanufactured transmission. Vehicle has 230k so I figured that was coming. Picked it up, drove about 10 miles home, no problem. It sat for a day or two. I went to drive it and the same problem started again. Had the vehicle towed back to the shop and it ran fine on a test drive. Mechanic took it home and the next morning the problem started again (at least they see I'm not making it up). I checked the V4-V8 mode while it was misbehaving and it was show in V8 mode, so I don't think it is the AFM acting up. Shop has been looking at it for several days and seems to be stumped. Had a motor mount changed several weeks ago. Wondering if something could have gotten pinched during that process (wiring or a fuel line). Throttle position sensor checks out. I asked them to check the fuel pump and catalytic converter (maybe it is clogged up). No idea where to go from here. Thanks.

the MAF can be the cause of this exact problem, just something to have them look at, could be a lot of things though could be wiring if it makes a little ways just enough for the wire or module to heat up and loose contact or create resistance. battery cables should be checked, mega fuse, grounds.

 

[tbgrey2007]

Checked in with the shop today. They put in a second transmission thinking they got a bad one, still same problem. Mechanic said when giving it throttle, the computer shows it as being 100%, but the actual throttle input is fluctuating up and down and usually no more than 10%. Computer doesn't show why it is restricting the throttle. They double checked the throttle bottle and position sensor and downloaded the updated software from GM. They checked the fuel pump and for any vacuum or sensor connector wires issues. Not AFM related. I guess the only positive is that the condition seems to be more consistent, rather than intermittent. A mystery wrapped in an enigma. How can I be so lucky? Any other ideas???

 

[Geotrash]

Checked in with the shop today. They put in a second transmission thinking they got a bad one, still same problem. Mechanic said when giving it throttle, the computer shows it as being 100%, but the actual throttle input is fluctuating up and down and usually no more than 10%. Computer doesn't show why it is restricting the throttle. They double checked the throttle bottle and position sensor and downloaded the updated software from GM. They checked the fuel pump and for any vacuum or sensor connector wires issues. Not AFM related. I guess the only positive is that the condition seems to be more consistent, rather than intermittent. A mystery wrapped in an enigma. How can I be so lucky? Any other ideas???

If the throttle input is fluctuating, I would suspect the accelerator pedal.

 

[tbgrey2007]

If the throttle input is fluctuating, I would suspect the accelerator pedal.

Is that a sensor if some sort?

 

[Geotrash]

Is that a sensor if some sort?

More Information for GM GENUINE 25832864

 

[OR VietVet]

Thought I was gonna be a hero for a second, but @Geotrash beat me to it. I would bet, this part is the problem. Called a throttle pedal pressure sensor. Part of the "drive by wire" system.

 

[tbgrey2007]

Thought I was gonna be a hero for a second, but @Geotrash beat me to it. I would bet, this part is the problem. Called a throttle pedal pressure sensor. Part of the "drive by wire" system.

I called the shop and asked them to check it or if they already have. They surely have to be running out of things to check by now. Maybe the it needs a new ECM. Who knows.

 

[OR VietVet]

Something to always remember, ECM can go bad but it is very rare.

 

[tbgrey2007]

This started a week or so after I had the driver's side motor mount changed. Anything along the firewall that might have gotten pitched or nicked when they jack the motor up to make room for the new mount that might be causing the problem? The mechanic said it is like the ECM is fluctuating the throttle input to the engine, but not throwing a code as to why.

 

[Fless]

Get out a good scan tool and graph the throttle position sensor (for smoothness) through its range, and compare that to the throttle body throttle position sensor to see how they track alone and in concert with each other.

 

[swathdiver]

Checked in with the shop today. They put in a second transmission thinking they got a bad one, still same problem.

Their initial diagnosis for these symptoms was to replace the whole transmission?

 

[Trey Hardy]

I had similar issues I resolved mine from replacing the throttle body cleaning the maf and cleaning the air filter

 

[tbgrey2007]

Their initial diagnosis for these symptoms was to replace the whole transmission?

The initially changed the throttle body. I picked it up and did not even get a 1/4 mile down the road and the problems started again. After that the shop thought it was slipping in second gear. There were shavings and clutch material in the pan and they had issues with it in reverse. I don't doubt the tranny was going to need replacing at some point (231k), but it had been shifting fine before these issues started. Guess I'll call the transmission replacement preventive maintenance.

 

[swathdiver]

The initially changed the throttle body. I picked it up and did not even get a 1/4 mile down the road and the problems started again. After that the shop thought it was slipping in second gear. There were shavings and clutch material in the pan and they had issues with it in reverse. I don't doubt the tranny was going to need replacing at some point (231k), but it had been shifting fine before these issues started. Guess I'll call the transmission replacement preventive maintenance.

No matter how nice these fellas are, I think you need to take it to folks who are better trained. A trip to your local dealership probably would have you back on the road by now. They will use their bi-directional scan tool to pull any internal codes and follow the troubleshooting guide before throwing parts at it.

What state do you call home?

 

[tbgrey2007]

No matter how nice these fellas are, I think you need to take it to folks who are better trained. A trip to your local dealership probably would have you back on the road by now. They will use their bi-directional scan tool to pull any internal codes and follow the troubleshooting guide before throwing parts at it.

What state do you call home?

I'm in NC, outside Charlotte. I called the shop this morning and they are replacing the ECM. They did try a second throttle body and the problem got worse. Hoping to get it back today or tomorrow depending on when the part comes in. If this doesn't work I don't think I have much choice but to take it somewhere else. Tomorrow will be 3 weeks in. Fingers crossed.

 

[tbgrey2007]

Shop ordered an ECM and it appears to have fixed the problem. They are going to keep it over the weekend and start it and drive it some more to make sure. Wondering if I take it to the local dealer for a once over on the wires/lines to make sure there isn’t something still lingering just for the piece of mind. Thoughts??

 

[tbgrey2007]

Just an update. New ECM appears to have done the trick. Shop charged me for the part and programming (at a reduced price). My radiator sprung a leak while they were trying to figure out what my original problem was so they replaced that free of charge. I felt like that was fair after 3 weeks of back and forth.