99 Chevy Truck Help!

[SGRIM]

Need some help from the super mechanics here at TB:biggrin:

My 99 Chevy 1500 truck with the 5.3 motor runs great until I stop and let it idle for say 10mins or so. Then it starts to run like crap... No check engine light and no codes at all in computer

It acts like it isn't getting fuel. As long as you barely hit the pedal it is fine. As soon as you give it any throttle it starts to stall and the trans will drop down into a lower gear and it will rev up to like 3500-4000 and just hang there no matter how hard you mash the pedal Then "sometimes" it will go to popping too.

You come home let it set over night, runs fine until I let it idle for a while again

Until it starts the problem this truck runs like a scalded dog:biggrin: It has a program in it and a few other minor mods. This issue started out of the blue though, I have had the mods for years...

Please help and TIA!

 

[Daniel Jost]

Good chance it could be a fuel pump, pull the fuel pressure guage off your gn and check it. Also regulators are a big issue, does it start kinda crappy or have fuel in the regulator vacuum line? Those are signs of failure. Also knock sensors and maf sensors are known to fail. Do you have a scan tool? Check for a ton of retard, knock sensors have a bulletin because they get water down in them and they rust since the foam under the intake doesn't allow it to evaporate. Hope this helps.

,Dan

 

[SFITurbo]

start simple...fuel filter, I had a transmission rebuilt for $1700 because I had a high rpm shift problem Found out that was all that was wrong:frown:

 

[charlief1]

First take the programer off Shane. That will eliminate it as a possible cause. Then check the fuel pressure. It's unusual but I have seen programmers mess up like this before.

 

[TurboTnZ06]

X3 on a fuel pressure check.

I had an intank baffle come loose in my truck once, knocked the fuel pump and hangar badly, but it would have enough pressure to idle, and drive for a minute, but as soon as I hit the gas, it would fall on its face but then still idle.

 

[bogies87]

Also check the converter.......

 

[pdzz]

Drive it with a fuel pressure gauge taped to the window. Also, These symptoms could be caused by a plugged cat. MAF readings will be low, back pressure check should be below 1-2psi. Hope this helps, good luck. Phil.

 

[forcefed3.8's]

Coolant temp sensor going haywire? I have seen it on LT1's.

 

[DailyDrifter]

Hook a scantool up and look at the Fuel trims, then look at the O2s when the problem starts.

 

[Turbo317]

those trucks will still run on 35psi or so of fuel pressure when spec is 60psi ish.
check fuel pressure and fuel trim and go from there.

 

[chopped39]

Watch the fuel trims real close on bank 2 .When the pumps take a crap bank 2 will starve for fuel. that bank is fed fuel last. the ms on injectors will increase also. Do you have a cold air kit with a kn type filter. If there is an oiled filter the oil can get on mass air and cause all kinds of problems. Perform a fuel pressure test and a volume test also. Perform a backpressure test when this happens. You will have to check both side for back pressure because there are two cats. when it pops ,is that out the intake or exhaust? these things dont like less than 60psi. You might have 60 psi but no volume.good luck

 

[SGRIM]

Wow, thanks for all the replies. We are going to try these things tomorrow. I will post results...

The popping feels like it is coming from underneath my feet so I guess that would be more of an exhaust pop....

I suspected the cat converter(s) but in my experience they always casue the idiot light to come on. It has yet to come on one time during all this. I guess that is why I feel like it is a fueling issue too... Just don't understand why it takes so long for it to act up...

 

[Turbo-Archie]

I got the new style 99 1/2 Z/71 at my old work.

I loved that truck but it was plaged with problems.

The fuel pump started to go out at 3k miles!!!
With mine, it just wouldn't start cold on the first try. It would only start on the second..


The truck was a lemon, fuel pump, steering shaft, pulled hard to the right, window got stuck down, Dr mirror popped out when I shut the door, Dash filter needed to be replaced BS, drive shaft knocking,

 

[austinibew145]

I had same problem with my 2000. The regulator went bad. Pull the vacume line see if fuel comes out, common problem.

 

[chopped39]

I had same problem with my 2000. The regulator went bad. Pull the vacume line see if fuel comes out, common problem.

X2 and if you replace it be real careful not to drop little o-ring in the fuel rail. Ask me how I know :biggrin:

 

[snyderjw1]

....sounds like cat to me as well. You could drop the pipe (where the y goes into cat) or pull an o2 out when it's acting up and see how it runs...

 

[s10GN]

I had a 99 zr2 with a similar problem starving for gas, breaking up , sputtering no codes I replaced the spider. I am not sure if that year 1500 has a spider or rail?

 

[RIFF RAFF]

X2

Drive it with a fuel pressure gauge taped to the window. Also, These symptoms could be caused by a plugged cat. MAF readings will be low, back pressure check should be below 1-2psi. Hope this helps, good luck. Phil.

THATS WHERE ID START . DROP THE PIPE .. CHASED ONE JUST LIKE IT . CHITTY GAS ANYMORE..

 

[novaderrik]

I had a 99 zr2 with a similar problem starving for gas, breaking up , sputtering no codes I replaced the spider. I am not sure if that year 1500 has a spider or rail?

nope- the "LS" 5.3 in the 99 trucks finally have true multiport fuel injection like Buick was using on turbocharged Regals in 1984..

 

[RIFF RAFF]

Well shane

Hows the truck? What did you find? Tuned in