Poor Performance, Gas Mileage, 1995 Silverado V8

[pplassm1979]

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]

Tune up

[pplassm1979]

Tune up

 

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

[bill190]

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]

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!

+1 on that stuff. Also have your checked your cats? Plausible that old of a truck has plugged converters.

[pplassm1979]

Thanks for the suggestions. I was leaning in the direction of suspect converter, myself.

 

Unfortunately, I cannot work on the truck myself at this time (hand operation yesterday). I will talk to my mechanic about it.

 

Thanks again.

[Stevens03]

I'd check the cats first.. then go over the listed items above. Clogged cats could/would cause BAD performance.

[superjim]

+1 on checking the cats.

Sounds almost like the classic symptoms of cat stopping up.