Poor Performance, Gas Mileage, 1995 Silverado V8

pplassm1979 · May 18, 2009

Truck: 1995 Chev. Silverado 2500 Extended Cab w/5.7 liter V8, 4 speed automatic. 145,000 miles.

Truck will not pull above 2400 RPM. Acceleration is "leasurely". When going up hills, going down a gear result in the truck slowing dramatically. On a recent trip, this resulted in difficulty maintaining highway speeds. Truck was lightly loaded.

Truck also takes a while to start (10-15 seconds) and runs rough when cold.

I have taken the truck to my local mechanic, who has been good in the past. He put the truck on an engine analyzer, and replaced the "Manifold Pressure Sensor". This has not netted any improvement.

It's almost as if the ECU is in some kind of self-protect mode.

Any ideas where I should start?

Thanks

PP

Draenor · May 18, 2009

Tune up

pplassm1979 · May 18, 2009

Tune up

Something specific to look for? Plugs/wires have been changed, air filter cleaned. What else should be done?

bill190 · May 18, 2009

There are things which should be checked/serviced regularly, so I would do that anyway, but these probably will not fix the problem...

Replace fuel filter if not replaced recently.

The oxygen sensor should be replaced every 60,000 miles.

Clean/replace PCV valve and associated tubing.

Then check all vacuum tubing for cracks or leaks.

Visually check all engine area electrical wiring for any bare or burnt wires, good connections.

Then if you are still having the problem (probably) and you want to work on your vehicle yourself, I would suggest getting a GM Factory Service Manual Set (4 books) from your GM dealer.

Then in the GM Factory Fuel and Emissions Service Manual, look for "Drivability Symptoms", then the problem(s) you are having with your vehicle. Then test/service everything suggested in the book.

The main tools to test with are a multimeter (voltage, ohms) and a fuel pressure gauge.

It will take awhile to order your service manuals. In the mean time, I would start by testing and servicing the fuel system (if above did not help solve the problem). Following is a good write-up on servicing the fuel system...

http://www.asashop.org/autoinc/june98/techtotech.htm

When your books arrive, one will list regular service items per the mileage. These are things to check/service/replace every so many miles. Keep up with this stuff on a regular basis and your vehicle will "purr" like a cat!

svensk · May 18, 2009

There are things which should be checked/serviced regularly, so I would do that anyway, but these probably will not fix the problem...

Replace fuel filter if not replaced recently.

The oxygen sensor should be replaced every 60,000 miles.

Clean/replace PCV valve and associated tubing.

Then check all vacuum tubing for cracks or leaks.

Visually check all engine area electrical wiring for any bare or burnt wires, good connections.

Then if you are still having the problem (probably) and you want to work on your vehicle yourself, I would suggest getting a GM Factory Service Manual Set (4 books) from your GM dealer.

Then in the GM Factory Fuel and Emissions Service Manual, look for "Drivability Symptoms", then the problem(s) you are having with your vehicle. Then test/service everything suggested in the book.

The main tools to test with are a multimeter (voltage, ohms) and a fuel pressure gauge.

It will take awhile to order your service manuals. In the mean time, I would start by testing and servicing the fuel system (if above did not help solve the problem). Following is a good write-up on servicing the fuel system...

http://www.asashop.org/autoinc/june98/techtotech.htm

When your books arrive, one will list regular service items per the mileage. These are things to check/service/replace every so many miles. Keep up with this stuff on a regular basis and your vehicle will "purr" like a cat!