capt- no I didnt look at the retardation. no scan tool for that only timing light and it was on the money.

 

My 95 blazer sometimes chatters off the line at a light. The truck shakes violently for a few seconds under normal acceleration. The problem is in the transmission. I have a leak and when the fluid level gets low the pressure is not where it needs to be and the clutches do not engage fully, this causes the shaking. When fluid level is low I can be driving and watch and hear the increase and decrease in rpm. It's like it cannot keep itself in OD. When I accelerate and the trans pump is moving faster the pressure increases and there is no problem. I just keep adding transmission fluid. I know how to rebuild these transmissions but not for this circumstance. I check the fluid regularly now. This motor and trans is coming out soon anyway. Even if your fluid level is good you could still have trash in the filters causing this same situation. If the fluid level was ever low and the clutches were not fully engaging you have clutch material floating around in the transmission. This causes more problems. Now if you were experiencing this jerking and rpm changes and we could eliminate the transmission from the picture, agree with other posts.

 

Not sure how you could tell ignition timing was "on the money" without a scan tool. The PCM constantly changes ignition timing which makes a timing light a worthless, obsolete tool on this system. The only way to check ignition timing is with a scan tool. If camshaft retard is adjusted correctly, ignition timing is accurate and correct. If camshaft retard is off, ignition timing is off, that's why I asked if you checked it. Might want to double check fuel pressure and leakdown too. Highly unlikely for KOEO fuel pressure to remain the same 10 minutes after the pump shuts off.

At this point, you need to rent, borrow, or buy a scan tool that is capable of viewing live data, including camshaft retard, to diagnose the problem. The el cheapo $300 to $400 scan tools that the auto parts stores use, are not capable of accessing camshaft retard.

 

As far as fuel is concerned, we checked it 3 times and it's good. Timing marks are on. Can the sensor that's next to the ign coil affect fuel trims or rpm?