Lost Acceleration

[Workhorse98]

I have a 1998 GMC Sierra K2500 pickup, I have replaced the engine and transmission about a 3 years ago. I have a problem with passing acceleration when the engine is operating at normal temperature rage and when climbing upgrade roadway. I will be driving and noticed the RMP will go up to 35k, then slip and go back down to 25K and continue to do this if I dont release the gas. It is sluggish when going up a hill. It usually get worse when driving on long trips or hauling my RV Trailer. Looked it everything, stuck. tested the fuel pump, i have spyder injectors, and replaced the distributor when the engine was rebuilt. need help, ran out of options. mechanics are stuck too.

 

[VIKING_MECHANIC]

First question: are you towing in OD? You should check the trans fluid(level and condition.) Do the RPMs drop like the trans is upshifting and then just revvs back up like it's downshifting?

When is the last time you checked the usual tune-up items(plugs, wires, cap and rotor)?

You tested the pump. Did hold pressure like in the spec? When's the last time you ckecked the fuel filter?

Engine oil level and condition?

Your next step would be to get a scanner with live data, pull any code(s) it may have and watch the live view for any out-of-place information.

 

[Schurkey]

1998 GMC Sierra K2500 pickup

WHAT ENGINE???

I have a problem with passing acceleration when the engine is operating at normal temperature rage and when climbing upgrade roadway.

High air demand, high fuel demand, throttle opened, high manifold pressure.

I will be driving and noticed the RMP will go up to 35k, then slip and go back down to 25K

??? Do you mean "RPM", 3500, and 2500?

If so, what do you mean by "slip"?

tested the fuel pump,

WHAT is the fuel pressure at prime, at idle, and under load. How old is the fuel filter?

i have spyder injectors,

Poppet, or electronic?

and replaced the distributor

What is the CMP Offset? Was that even checked when the distributor went in?

How old are the usual "tune-up" items and procedures?

Connect a scan tool, verify EVERY sensor and computer output. Look for misfire counts for each cylinder, and verify fuel trims when the engine is under load and acting-up.

 

[Workhorse98]

WHAT ENGINE???


High air demand, high fuel demand, throttle opened, high manifold pressure.


??? Do you mean "RPM", 3500, and 2500?

If so, what do you mean by "slip"?


WHAT is the fuel pressure at prime, at idle, and under load. How old is the fuel filter?


Poppet, or electronic?


What is the CMP Offset? Was that even checked when the distributor went in?

How old are the usual "tune-up" items and procedures?

Connect a scan tool, verify EVERY sensor and computer output. Look for misfire counts for each cylinder, and verify fuel trims when the engine is under load and acting-up.

5.3 engine, not sure on the poppet or electronic

 

[Workhorse98]

5.3 engine, not sure on the poppet or electronic

RPM

 

[Workhorse98]

First question: are you towing in OD? You should check the trans fluid(level and condition.) Do the RPMs drop like the trans is upshifting and then just revvs back up like it's downshifting?

When is the last time you checked the usual tune-up items(plugs, wires, cap and rotor)?

You tested the pump. Did hold pressure like in the spec? When's the last time you ckecked the fuel filter?

Engine oil level and condition?

Your next step would be to get a scanner with live data, pull any code(s) it may have and watch the live view for any out-of-place information.

It has auto OD, to your second question, yes. turn up about a year ago, Tested the fuel pump and its good, switch engine out every 300k, synthetic oil,

 

[Workhorse98]

It has auto OD, to your second question, yes. turn up about a year ago, Tested the fuel pump and its good, switch engine out every 300k, synthetic oil,

OIL not out

 

[GoToGuy]

300K is 300,000. Check your writing before posting . K is kilo = thousands. 25K RPM = 25,000 RPM .
Do you have 5.0. or. 5.7, 5.3 is LS engine, or do you have a conversion. Do you tow in 3rd or 4th/ OD ?
RFTQ