1996 Suburban Stumble & Shudder

[Drastic396]

I have a 96 Suburban with a 5.7. My wife and kids normally drive it. I recently change the intake gasket – it was leaking water. Now a couple of new(?) problems have occurred. The first is that from idle, the engine stumbles when it accelerates in neutral or drive, then it accelerates normally. It feels like a carbureted engine with a bad accelerator pump. I checked the TPS with a meter and checks ok. Just for kicks, I took one off of my '99 Tahoe with no change. The fuel filter was replaced as well. There are no vacuum leaks or other obvious problems. No change…

 

 

 

The second issue is that when the car reaches 50 to 60 mph, it shudders. It feels like a hard shift. I thought it was a torque converter lock-up issue. I changed the TCC solenoid, and filter with no difference. I did a lock-up converter test. Driving at a constant speed, I tapped the break pedal, the rpm would go up about 100-200 rpm, but there was no shudder when the t/c locked back up. It only does it when you level off the throttle and it lock-ups or OD engages? I can feel all the shift points.

 

 

 

I have ScanXL software. The only thing I notice is that the timing is -21.5 deg. On my 99 Tahoe, it runs 22 deg. All the other autos I have checked, the timing is a positive number. Could this be the problem and how do I fix it. I have moved the distributor, but the timing does not change -21.5 deg. Where do I go from here?

 

[cammiller]

The distributer on those only provides base timing. On our scan tool, it shows a cmp offset. This should be 0. If your scan tool shows this, set this to 0. Did you damage any ground during the intake gasket change? Did you check that there is no vacuum leak inthe the crank case?