I have a 90 4.0 that I having a tough time starting after it's warm. Starts cold, starts hot. The strangeness is if I try to start when warm, or after it has been sitting in the sun on a hot day, it cranks and fires then as soon as I move the key from start to on position, it dies. If I leave the starter engaged after it starts, it keeps running (I hate putting the starter and flywheel teeth through that kind of cycling). I get lucky and it will stay running 'sometimes' after keeping the starter engaged for about 15 seconds after the engine is running. Once in a while it dies out while driving in the warming up stage. So here is what I've done/tested thus far, chime in renix gurus please:
1. Pulled and cleaned out all the hard plastic tubes to the tb and airbox (that whole grouping of tubes) with mass air flow sensor cleaner.
2. Sprayed out tb and cleaned the stepper motor on the tb (no carbon on the pintle part is 1-2 years old).
3. Put on a new crank position sensor.
4. new coolant reservoir and cap, I could hear mine hissing and noticed fracturing had to fill the old one once. I had to sand the new reservoir opening with 600 grit on a block of wood to get the casting/molding imperfections out, got a tight seal with the cap now. What is it with those reservoirs made in Spain?
5. checked to see if I had an air pocket under the coolant temp sensor (the one for the gauge on top of the block)
6. Checked with voltmeter the tps was in spec
7. Fuel pressure 39 psi and it jumped 10 with vacuum line removed
8. Pulled cleaned and tested IAT sensor.
9. Tested the MAP, in spec.
10. Recent oil change.
11. New air filter.
1. Pulled and cleaned out all the hard plastic tubes to the tb and airbox (that whole grouping of tubes) with mass air flow sensor cleaner.
2. Sprayed out tb and cleaned the stepper motor on the tb (no carbon on the pintle part is 1-2 years old).
3. Put on a new crank position sensor.
4. new coolant reservoir and cap, I could hear mine hissing and noticed fracturing had to fill the old one once. I had to sand the new reservoir opening with 600 grit on a block of wood to get the casting/molding imperfections out, got a tight seal with the cap now. What is it with those reservoirs made in Spain?
5. checked to see if I had an air pocket under the coolant temp sensor (the one for the gauge on top of the block)
6. Checked with voltmeter the tps was in spec
7. Fuel pressure 39 psi and it jumped 10 with vacuum line removed
8. Pulled cleaned and tested IAT sensor.
9. Tested the MAP, in spec.
10. Recent oil change.
11. New air filter.