throttle body on gmc 5.3l clenaing similar concept to others?

[Soundguy]

it would come on at startup, and then *sometimes* go off by the end of the day, per the wife.

I didn't even know the truck was running bad till i got in it to move it one morning a few days ago and it fell on it's face. I asked her how long it had been doing it and she had an inexact time frame

I mentioned that i really need to know when the things don't work right, and soon, incase it was soemthing serious.. like.. lack of oil or something.. especially since that 5.3 is a lush!

 

[crashz]

Last run cycle to the post cleaning run cycle messes with the amount of airflow at startup and fast idle. When the computer sees that delta without a change in the idle air control, it sets the CEL.

I was having a heck of a time with the fuel cap and evap system for a while with my 04. There is an updated vent tube that I was going to install, but I also found that the seal at the gas cap was allowing slight pressure through. Changed the cap with a factory unit and not more CEL.

 

[Soundguy]

funny.. my wife sometimes left the cap off and got theevap error.. so she got used to ignoring the ce light.

well.. check the cpu.. codes were 4

tps signal low, lean bank a, lean bank b, and IAC idle high.

I cleared them.. truck seems to be running fine.. though on the way to dinner, when we puleld into the restaurant.. engine was idling way high.. was normal at startup?

engine computer re-learning since i've cleaned all the junk out of the iac and throttle body?

whole new ballgame for it?

 

[inane2]

J

Most definitely don't use a wire brush! It will remove the coating. I use a soft plastic brush, like an M16 cleaning brush and throttle body cleaner. FYI when I worked for a GM dealer there was a lot of those that came in because of poor idle and starting. The gunk had caused a ridge to develop and the butterfly wouldn't close completely at idle and start, therefore the air mixture was off. They would counter by adjusting the throttle plate to stop in a different position but then there is a little hole in the butterfly plate that was either plugged by a screw or you had to take a screw out, can't remember which.

Anyway, I'm sure you could google for TSB's or go to a chevy forum.

Stihlrunner is right on the money here.

I work as a fleet mechanic for a large company that maintains their own vehicles. In 1999, when the 5.3 was introduced, they bought around 25-30 half ton trucks and a few Tahoes and Suburbans. I most certainly remember most all of the 5.3's coming back in after 50,000 miles or so with the same issue. Sometimes the throttle body would be so gunked up, the butterfly wouldn't open smoothly, the driver would push harder on the accelerator and finally when it opened, it would take off near WOT!

Seems like I was seeing this on the 99' - 00' models frequently, less frequent on the 01's and 02's. Crazy thing was that the 4.8's and 6.0's were few and far between with the issue. The company did have some 02' Escalades with the 6.0 and they were drive by wire, where the other trucks and SUV's still had a mechanical throttle cable. These 6.0's had the same issues as well, they would idle terrible low, around 500 rpm (the AC compressor would often kill the motor). Anyways, if you could keep them idling, it would take off hard.

Each of us just kept throttle body cleaner in our tool carts and we could get them in, clean them and get them out quickly. They don't like starting with all the cleaner down their throats but once you cleared them out, they were good as new!

 

[Soundguy]

yep.. this is a 00 model.. and it was dirty around the butterfluy.. good thick ridge...

for sure needed cleaning..

 

[94BULLITT]

funny.. my wife sometimes left the cap off and got theevap error.. so she got used to ignoring the ce light.

well.. check the cpu.. codes were 4

tps signal low, lean bank a, lean bank b, and IAC idle high.

I cleared them.. truck seems to be running fine.. though on the way to dinner, when we puleld into the restaurant.. engine was idling way high.. was normal at startup?

engine computer re-learning since i've cleaned all the junk out of the iac and throttle body?

whole new ballgame for it?

Does your scan tool have a data stream? If it does watch tps voltage throughout the entire range of the the gas pedal, you can do this key on engine off. A bad tps could cause you 02 sensor codes and a high idle. While you have the scan tool hooked up you can watch the 02 sensors while it is running too, but address the tps code 1st. A vacuum leak will cause lean exhaust and high idle but not a tps code. Your tps voltage should be .5v at closed throttle to 4.5-5v WOT. If your scan tool does not have a data stream you could check the voltage with a multimeter but I will have to look and see what wires you need to probe.

 

[Dr Dave]

Check your fuel pressure regulator for leakage,remove the vacuum hose from the regulator and see if fuel is leaking out. They can bleed off fuel pressure and fill the intake with fuel. If it is leaking and backfires on startup, it can blow the plastic plenumn into hundreds of peices. This can cause, rich and lean codes.

The TP and IAC codes may be related to the sludge in the throtle bore.

Dave

 

[Soundguy]

i *think* my tool will stream. will check when the wife gets back from a conference in tampa in a couple days.


I will add that no more codes set after driving to and finally back from dinner, after erasing them. seems every run it's getting a lil better.

will for sure keep an eye on it.. and if back on sunday will throw the scan tool back on and see if it will stream