98 c1500 lopes like a dragster.

[Chuck p]

I bought a 98 1500 with a 5.0 ran when i looked at it. Picked up the next day fuel pump was out. Truck ran but poorly when i checked it. Changed fuel pump truck runs but lopes heavy. No cam in it but sounds like it. Smelt fuel found injectors were bad and leaking. Replaced spider still ran the same for about 5 minutes then cleared up and purred like a demon kitten. Drove truck 1 mile ran fine. Parked and qhen restarted back to loping. On live data stft at -31 both banks map at 20 when it clears itself up map at 10 fuel trim at -3 to 3 both ltft and stft. Have gotten code p0300 and p1351 only when it's loping. When its in that mood it starts and dies or tries to. When its in a good mood runs perfect starts quick no issues. The fuel system is new delphi pump new style delphi injectors. New crank purge map and ect sensors both ect. New egr new plugs wires rotor cap. New iac. New coil and icm. New O2 sensors as well. Only parts not replaced are maf iat and cam sensor. No cgamge when i unplug maf so i ruled that one out. All my grounds check good. There is no play in the distributor when i try to move rotor. . Im leaning toward either cam sensor or pcm. Tight on cash and wifes gettin tired of it not being reliable. Need help please i want to fix my baby.

 

[stutaeng]

Sounds like multiple issues...

So you get STFT at -31% both banks initially? Lean codes are typically vacuum leaks. But then they go to -3 to +3? Is that after it warms up? have you checked for fuel pressure during this?

Intake manifold gaskets will sometimes leak on cold engine and then seal themselves up when engine gets hot and expands the plastic.

I'm still reading....Damn, you've replaced all the sensors, it sounds like! LOL. Why? If you can see live data and see meaningful information, there's no reason to replace most or all of them sensors. Purge solenoid, for example, has nothing to do with engine running. Oh, well.

Looks like you haven't replaced the distributer? You said no play? Sometimes the gears get worn and can cause intermittent stalls. (A new distributer will come with a cam sensor BTW.)

The camshaft position sensor is for spark advance. I had one intermittently fail on my 4.3 Vortec. The truck felt like it wanted to die, but then kept running. I don't think that would be the problem as far as what you describe. And mine threw a cam code...

What are your values for the MAF on your scanner? Does it change with accelerator position?

Welcome to the forum BTW!

 

[Chuck p]

Thanks. Map and purge changed due to extreme raw fuel smell in them from bad refulator in old spider fuel pressure is 62 koeo 58 to 64 whwn running no matter how it's running. Iac pimtle had come out ckp was scarred a little. Distributor is 7 years old and yes no play i mean the rotor wont wiggle at all. Crazy part is cold or hot it either runs great or like the egr is stuck open. Its like its stuck in flood status and i will check the maf to get exact numbers but i know they change with acceleration. Its really kinda like its out of time thats why im thinking cam senaor.. Not sure if Distributor was new or used replaced by previous owner. I have checked grounds and all and as long as its in a good mood it will starr and run beautifully 5 minutes or 5 days after turned off. If in a pissy mood starrs right up tries tp die if it does will restart and run if i tap pedal as soon as ut starts. Tps is at 0 tp 2.2 depending on if its 65 or warmer pr engine is warm when started.

 

[Chuck p]

And o2 semaor cause ls up and poat cat were black with soot

 

[Schurkey]

Its really kinda like its out of time thats why im thinking cam senaor..

This is a Vortec engine...right?

Cam sensor has NOTHING to do with ignition timing.

Tps is at 0 tp 2.2 depending on if its 65 or warmer pr engine is warm when started.

No idea why the TPS changes with temperature.

 

[Schurkey]

Double post, sorry.

 

[Chuck p]

Yep 5.0 vortec . some days u start it it runs perfect some days you start it and it inatantly is subtracting all the fuel from the engine which is in my opinion whats causing it to lope. Thanks for everyones i put greatly appreciated

 

[stutaeng]

Look at your fuel trims when it does this...does revving the engine make the fuel trims any better?

If so, then most likely vacuum leak.

If not, then usually a fuel problem.

 

[Schurkey]

I'd be looking at misfire history in particular, all the rest of the data stream in general. I'd want to know fuel pressure and verify all the usual "tune-up" items.

 

[ccreddell]

If its a Vortec, you might have lost intake manifold gaskets. It'll give you a heck of a vacuum leak too...