1991 Chevrolet Truck

Year 1991
Make Chevy
Model S-10 (2-WD)
VIN 1GCCS14A4M0195011
Engine 2.5 liter
Mileage 200,000
My truck would start and idle just fine. When cold it will take off from a stop. It may not be running exactly right but at least it can move itself. Once up to temperature it has a very difficult time moving itself from a stop. If I feather the gas pedal, with great effort I can get the truck moving from a stop. If I just press the gas pedal gently from a stop the engine stalls. It can be restarted immediately but will stall again unless the gas pedal is feathered.

My engine is fuel injected but the symptom seems very similar to that of a carbureted engine with a bad accelerator pump.

Below is a history and troubleshooting thus far.

Tune Up
Replaced oil and filter, anti-freeze, spark plugs, air filter, fuel filter, PCV valve. Truck was taken on trip to Death Valley. Truck ran fine and had no problems.

10-26-05 Trouble appeared
Replaced throttle body, injector and gasket, intake manifold gasket, EGR valve and gasket. Problem is still present.
Original parts re-installed.

Replaced EGR Valve, MAP Sensor
Problem is still present.
I was told exhaust manifold was cracked and O2 sensor needs to be replaced for $1000.00 more.

Replaced oxygen sensor.
Problem is still present.

Re-connected all connectors.
Truck is very hard to start.
I was able to get truck to start by spraying starting fluid inside air intake. Truck will idle but stalls when accelerator is pressed. Since it had been sitting so long, I thought trouble might be due to “old gas” so I added 2.5 gal of gas to the tank. It did not help.
May 5, 2007.

Start with a fuel pressure test. Sounds like the pump is weak and or the filter is plugged.

May 6, 2007.
Fuel filter was replaced just prior (about 500 miles) to start of trouble. Fuel pressure/pump is what will be checked next. Thanks

May 6, 2007.
Fuel filter was replaced just prior (about 500 miles) to start of trouble. Fuel pressure/pump is what will be checked next. Thanks[/quote: 39d45e9e06]

Changed fuel pump and strainer in tank. Truck now starts and runs with out stalling. Engine runs very rough and engine service light comes on a lot. I suspect that those who " worked" on truck earlier screwed up timing. Cap, rotor, wires, and plugs were replaced shortly befor stalling problem and have very little miles on them (about 500 miles.) I plan to inspect them as well as check timing with strobe and adjust idle. I'll also fill tank with fresh gas and add a bottle of fuel system/injector cleaner to gas tank.

Any ideas on other things to check/replace?

May 9, 2007.
Have you checked for vacuum leaks? Check by using spray carb cleaner or propane gas around all the hoses and gaskets of the intake area. If the RPM rises, there is a leak.

May 13, 2007.
Took truck to a shop and got it fixed. Trouble was vacuum hose to MAP sensor was connected to wrong vacuum port (should be manifold vs.?) When MAP sensor was replaced. Truck now runs OK. Next step is (CA) Test Only Smog Check.

Jul 12, 2007.