Truck stops accelerating

[armarm1]

I have a 2003 GMC Envoy. A couple of months ago I noticed I would press my gas pedal and it would be slow to get power. Its gotten worse now. I'll slow down and go to accelerate and the truck just smoothly rolls like its coming to a stop. I'll have to press the gas over and over again and it eventually moves. While I am pressing the gas the RPM is not moving. When the truck finally does jerk into motion thats when the RPM needle moves. There is no code showing. I've even taken it into Autozone and had them try to find a code but they don't show anything as well. This is getting to be very scary cause I feel eventually the truck will just finally come to a stop in the middle of traffic. I won't even get on the expressway anymore. We have statrted with the cheapest fix of changing the gas filter but that hasn't helped. Any suggestions? The truck is 2003 6 cylinder 4.2L engine S

[maxwedge]

Welcome to AF, this is impossible to diagnose from here, many things can cause what you describe, do you a fuel pressure tester? Do you have reasonable mechanical skills, how old is the fuel filter?

[Tech II]

Well, you shouldn't be driving this vehicle......

What I would do is go to a GM shop......set up the paper work so it doesn't have to be done later(nothing can be done or charged until you sign).....

THEN when the car acts up, call the dealership and tell them it is acting up, and see if you can bring it in immediately to be looked at....

[Blue Bowtie]

This is a throttle-by-wire scheme. There is a potentiometer connected to the accelerator pedal, inside the vehicle. Check the electrical connections, and try a plastic-safe electrical contact cleaner such as CRC QD on the potentiometer to see if it improves. You could also meter the resistance (engine off) as you move the pedal through the range.

It would also be helpful to inspect the electrical connector at the throttle motor, on the throttle body.

[Tech II]

Blue, usually the TAC system will set a code for this situation...he said there were none....

[Blue Bowtie]

...Unless it is slipping.

[Tech II]

Uh, exactly what do you think is slipping?

[777stickman]

How about a good Throttle Body cleaning?

[armarm1]

Originally Posted by maxwedge

Welcome to AF, this is impossible to diagnose from here, many things can cause what you describe, do you a fuel pressure tester? Do you have reasonable mechanical skills, how old is the fuel filter?

Thank you. The fuel filter is brand new. I just had it put in last week 7/18. I'm thinkiong of trying to replace the sensor next.

[armarm1]

Thanks. I will try this.

[armarm1]

Thank you so much. I will def forward this info on.

[Blue Bowtie]

Originally Posted by Tech II

Uh, exactly what do you think is slipping?

In Envoys /T-Blazers with adjustable pedals, the mechanism can slip past the accelerator sensor lever and not actuate.

[r0cdr]

Originally Posted by Tech II

Uh, exactly what do you think is slipping?

Sounds like it is going into "limp" mode. Happened to me intermittently for a few days then it flat quit paying attention to the throttle. I took an hour in very annoyed heavy LA traffic (I got off the freeway in time) to go the 5 miles to my shop - I was lucky to be so close. Throttle body assembly had basically fallen apart & the computer could see that the throttle didn't do what it was being told and went into limp mode. replaced throttle body assembly - cant remember what else as this happened several years and a 150000 miles ago. Not too unhappy as the truck had 200K rough miles on it, and its still going at 360K. Early 2002 model bought new. The poor truck really works for its cookies as I do a lot of 4wd mountain dirt roads.

[Tech II]

When it goes into limp mode, it will set a code....

[Blue Bowtie]

Slipping in a different location then.