sierraZ71SS

I have a 1999 GMC Sierra 1500 with a 5.3. Im wondering if my torque converter is going bad. At about 40 to 45 mph and on the gas lightly the engine stays at the same speed. But if I ease off the accelerator, the engine RPMs climb up a few and the engine tone changes. Im also having a lack of power too. The truck has 186000 miles on it, but the tranny only has 90000. It is the original torque converter. Also I have a few ticking lifters. I thought maybe the lifters are causing a false knock. I check igniton knock retard and ocasionally there is some. My scanner sucks so im not sure if it picks up any when the engines revs like it does at 45. But when it does rev up the igniton timing goes from say 45 to 55 degrees. Ocassionally at idle the truck will surge too. I really could use some help, Im stumped!!!!

sierraZ71SS

It dosent like to downshift real well either.

Z71/99

Dont have any help or advise but Im having the same type symptoms with my 04 5.3. I find that under heavy load at low to mid-high rpms at any speed it seemed to me like it was pulling timing for whatever reason because it physicaly stops pulling as hard with a deaper engine note like i let off the throttle a bit. I found that the (Drive by wire) throttle was actually closing ~ 5-15% for whatever reason but only with the A/C ON (all around 2000-3300rpms, with it off no such trouble and runs like it should and can actually make it up the hills around here w/o downshifting. Also in park I can raise the rpms anywhere in the 2000 range and keep the accelerater position sensor (gas pedal) perfectly steady or + or - 1% but the actual throttle position rises and falls the same 5%- 15% (with the rpms following around 500-1000rpm) on its own without me doing a thing. A/C off its as steady as the pedal.


Hopefully someone might have some advise or ideas sorry I dont.