Mechanics

MY 454 IS LOSSING POWER ON ACCELERATION. I'VE CHANGED MANY PARTS, INCLUDING ENGINE. NO POWER AND ENGINE BACKFIRES IF YOU HOLD PEDAL DOWN.

1992 GMC Truck • 195,000 miles

I changed orignial enging due to broken pistons. The same problem occured right before engine failure. I have changed, fuel pump, fuel filter, exhaust sys, O2 sensor, distributor assy, coil. No codes either. Idles nicely, jsut won't pull anymore or go up hills.
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Justfixit
September 22, 2011.



PS: the truck is a K2500 automatic.

Tiny
Justfixit
Sep 22, 2011.
Do you have TBI or multi port injection? Have you done anything with the injectors? Have you checked compression in the new engine? Is timing correct?

Thanks for responding! I do have TBI, original and changed the accelerator diaphram too. Timing is set properly, runs good when cold or flat ground. Just changed my MAP today, no avail?

Help

Tiny
Justfixit
Sep 22, 2011.
PS compression is really good! Only 85K on new engine.

Tiny
Justfixit
Sep 22, 2011.
Have you checked the catalytic converter? It could be plugging.

I'll find a temp lazer somewhere and check it out. However, not sure how it could be "plugging".

Tiny
Justfixit
Sep 25, 2011.
Todays ethenal fuel leaves lots of deposits. Heat gun won't do much to answer this however. Remove the O2 sensor and see if the power comes back if so the cat is pluged. It will be loud when you test drive it because of the O2 being removed just so you know.

Racefan966
Sep 27, 2011.
Thanks again for the tips. The heat gun said 425 and 420 out. New o2 sensor last week. Vacum lock maybe? But how do I prove it? Any suggestion are helpful.

Tiny
Justfixit
Sep 27, 2011.
Tell me what all you have checked so I know what to go over or not. Thanks

Racefan966
Sep 28, 2011.
OK, this is great. Replaced engine, Map sensor, O2 sensor, complete exhaust sys, new ignition coil, replaced pick up coil inside distributor, new wires/plugs, new fuel pump and filters, and replaced the press regulator inside TBI assy. Ignition timing has been triple checked many times again and again. To include retiming the engine with distributor. Still loss of power after engine warms up only, runs great when cold or at slow in town speeds. Thanks again for your time.

Tiny
Justfixit
Sep 29, 2011.
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