Help please

[breeze9]

I have a 95 Jimmy 4.3 that has lost all pick up. Can sit in and idles fine but can hold it to the floor and RPM's will only get to 2200. Tune up was done changed the upper intake gasket checked the spider have great fuel pressure with no bleed back. Cat is not plugged and the ignition module is new. No check engine light is on and tried new computer. Any help would be great.

[MT-2500]

Originally Posted by breeze9

I have a 95 Jimmy 4.3 that has lost all pick up. Can sit in and idles fine but can hold it to the floor and RPM's will only get to 2200. Tune up was done changed the upper intake gasket checked the spider have great fuel pressure with no bleed back. Cat is not plugged and the ignition module is new. No check engine light is on and tried new computer. Any help would be great.

Did it start before or after upper intake gasket?
Got good hot blue spark to all plugs?
What is engine vacuumn reading at idle and at 2K rpm?

What is the great fuel pressure reading in lbs cold start idle and fast speed up and running on the road?
Flat top dist or old style?
Was Timing or /camshaft retard setting checked or set after intake gasket?

[breeze9]

fuel pressure is 56lbs not sure on the vac. Has old style dist. None of the timing parts were moved. I took off the upper intake to check the spider and it had no leaks.

[MT-2500]

Originally Posted by breeze9

fuel pressure is 56lbs not sure on the vac. Has old style dist. None of the timing parts were moved. I took off the upper intake to check the spider and it had no leaks.

56 at where when and how?
Fuel pressure is low.
Run full fuel pressure check and post back all readings.
Hook up gage and tape it to outside mirror or outside windshield.
We need cold start and engine running and the engine running on road after hot and 30 more more minutes running.
Hard to start cold.
Check cold start fuel pressure.
Check engine running fuel pressure.
Check engine running on the road fuel pressure.
Then shut it off and watch for fast leak down.
Pinch off at rubber part or block off return line and check full pressure.
Later V6 and V8 gm engines with that engine code and year and make should have 55-66 fuel pressure.
Cold start should be 55/62 lbs of pressure.
If you do not have full fuel pressure on a cold start the injectors will not squirt fuel.
Do not leave home without it.
Engine running should be 55/62 lbs pressure depending on engine load.
Full pressure with return pinched off should be 75-85 or more.
And if it has a fast leak down after shut off you have a leak.
If pressure does not come up with return line pinched or blocked off.
Go to fuel filter and hook a gage direct to a line at fuel filter.
Pressure should come up to 75 or more and will hold after fuel pump is turned off.
If it leaks down there after fuel pump is turned off it is LEAKING BACK THREW PUMP CHECK VALVE OR PUMP MODULE LINES.
Post back your fuel pressure readings.
MT


Check that timing and engine vacuum and for hot blue spark tom plugs>

[777stickman]

I know you said that the cat is not plugged. But, from your 1st post it sure sounds like a restricted exhaust to me. Pull both upstream o2 sensors and see what happens.

Let us know.