plainsdrifter,
Here is the diagnostics for "Lack of Power, Sluggish, or Spongy" from my 90 Factory Manual.
- Check air filter
- Make sure both injectors are firing. If only one fires, swap electrical connectors to see if the other starts to fire (injector vs wiring to injector)
- Check Fuel Filter and Fuel Pressure.
- Check ECM Grounds.
- EGR Operation. Make sure it is not stuck partially open.
- Alt Output. Should be 12-16 volts.
- Engine Valve Timing. Perform compression test. (I would also add a worn timing chain would be the what will cause valve timing issues)
- Check Camshaft (look for worn lobes).
- Check secondary ignition voltage. (Coil Output and voltage reaching the plugs)
- Check Torque Converter operation. If it is locked up, it can seem like the engine has no power.
- Check exhaust for restriction.
You can check the exhaust using a vacuum gauge.
1. Hook it up to a vacuum port and warm up the engine.
2. Run engine at 1000 RPM and note the reading.
3. Increase RPM to 2500 slowly. Note the reading at a steady 2500.
4. If the difference in pressure drops more than 3 inches at 2500 than at 1000. The exhaust should be checked for restriction.
5. Disconnect exhaust pipe for engine and repeat steps 3 and 4. If the reading is still 3 inches or more that in Step 2, check valve timing.
My gut feeling is that this is fuel related. Replace the filter and check the pressure. Check the fuel injectors, you might be only running on 1. Your pump could also be on the way out.
How does it run cold? A clogged cat sometimes will be ok cold but the truck will run worse when the cat gets hot and starts to clog.
Unfortuately, you need a special tool to read the fuel pressure (along with a fuel pressure gauge). If you on this page you will one
http://www.mytoolstore.com/toolaid/diagn01.html #37650.
Good luck and keep us posted.
//2000CAYukon