No Power At Free Way Speeds

[mdeanh]

Hello,

I have a 1988 gmc s15 ext cab truck w/ 2.8 engine.

I took the truck out on the free way and was lucky to get up to 55 mph.

The tranny shifts up and down fine but the rmp is higher than usual almost double at highway speeds.

I replaced the engine and tranny about 35,000 miles ago but has been sitting for that last few years.

I recently just replaced the sending unit and fuel pump, fuel filter and rebuilt the throttle body.

I even took off the muffler and tested it out on the freeway again with no improvement.

So i think the cat may be starting to get plugged but not to sure if it is the problem, according to others report of no power etc.

Ive also heard the o2 sensor could be going out allowing to much gas through?

 

Any one have any suggestions.

Thanks in advance

 

Matt

[ems90S15]

Hello,

I have a 1988 gmc s15 ext cab truck w/ 2.8 engine.

I took the truck out on the free way and was lucky to get up to 55 mph.

The tranny shifts up and down fine but the rmp is higher than usual almost double at highway speeds.

I replaced the engine and tranny about 35,000 miles ago but has been sitting for that last few years.

I recently just replaced the sending unit and fuel pump, fuel filter and rebuilt the throttle body.

I even took off the muffler and tested it out on the freeway again with no improvement.

So i think the cat may be starting to get plugged but not to sure if it is the problem, according to others report of no power etc.

Ive also heard the o2 sensor could be going out allowing to much gas through?

 

Any one have any suggestions.

Thanks in advance

 

Matt

 

Either gut the cat or replace it, if it's any wheres pluged up, that's your culprit.

I've seen people try diving their vehicles with a cat that was just rattling inside,I could light a cigarette off of it.

[superjim]

I took the truck out on the free way and was lucky to get up to 55 mph.

 

So i think the cat may be starting to get plugged but not to sure if it is the problem, according to others report of no power etc.

 

Thanks in advance

 

Matt

 

 

Take it to a muffler shop.

 

They have a BACK PRESSURE gauge that they can put in the exhaust pipe and check the flow of the CATS.

[mdeanh]

Ok, now im really confused...

I pulled the muffler off and poked out the cat, reinstalled the muffler and still no difference.

I still have no power getting past 55 mph, does any one have any other suggestions?

Like i said I just got done replacing the entire fuel system since its sat awhile.

The RPM's are still about double they should be but the tranny seams to shift fine from low speeds untill 55 MPH.

Once I push the gas pedal to go faster, the tranny downshifts to try to get higher speeds but no go.

 

Thanks

Matt

[jerseymike68]

Thank You!