04 5.3 Sierra No Ignition Advance

hitempguy · November 16, 2008

Hi Tech dude ,

I have an 04 5.3 Sierra Crew Z71 with 4l65E. It acts like it has no ignition advance. When idling I gradually rev it up and it will go to a certain RPM and stay there. Push on the gas pedal a bit more and it will increase 500 rpm more then stay there. Any other vehicle I have, I touch the gas, it will rev right up to 3000 rpm(03 4.8 Sierra, 96 5.7 Sierra) My Cortex shows that it has advance. My '96 did the same thing and I had a weak timing pick up sensor.

-When cruising on the highway it also feels like it is being held back?????

Also when coasting down a hill on a highway, if I let my foot off the gas, the truck will slow down, and I mean a mountain road with a 7% grade, truck empty and the truck will slow right down. I watched the igniton timing on my superchips cortex while driving and the ignition timing turned back from 40ish to -10 degrees. I could understand this if I was in tow/haul mode, it would help control the vehicle on a steep descent if I was towing, but empty???WTH

redvett · November 16, 2008

First of all you have drive by wire and no throttle cable, the PCM controls the throttle opening and excessive RPM's in "N" as for going down hill the PCM controls the throttle to control emissions. If you feel it holding back its the torque management protecting the drive line. Are you sure its not a 4L60E? I dont think the 4L65E came in that model.

Hi Tech dude ,
I have an 04 5.3 Sierra Crew Z71 with 4l65E. It acts like it has no ignition advance. When idling I gradually rev it up and it will go to a certain RPM and stay there. Push on the gas pedal a bit more and it will increase 500 rpm more then stay there. Any other vehicle I have, I touch the gas, it will rev right up to 3000 rpm(03 4.8 Sierra, 96 5.7 Sierra) My Cortex shows that it has advance. My '96 did the same thing and I had a weak timing pick up sensor.

-When cruising on the highway it also feels like it is being held back?????

Also when coasting down a hill on a highway, if I let my foot off the gas, the truck will slow down, and I mean a mountain road with a 7% grade, truck empty and the truck will slow right down. I watched the igniton timing on my superchips cortex while driving and the ignition timing turned back from 40ish to -10 degrees. I could understand this if I was in tow/haul mode, it would help control the vehicle on a steep descent if I was towing, but empty???WTH

hitempguy · November 16, 2008

Yup, your right, it has the M30 (4L60E), I am also aware of the drive by wire. The "excessive reving" I am using is to 1200-1500 rpm. If I press the gas pedal slightly from idle the engine rpm will increase slightly, 550 to 1000rpm and then stay there. The '03 4.8 Sierra is also drive by wire and it will gradually sweep up and end up at about 3000 rpm doing the same thing. Even when driving it acts similar, no gradual increase in RPM. When this happened to other vehicles I owned, the issue was some sort of timing advance problem. The problem I have is there are no codes. If I had to compare, it's like the vacuum advance not working on an old style ignition system...

Why would torque management need to make the engine brake when cruising on the highway at 60mph? I let off the gas and want to coast down the hill and if the hill was a mile long and I was at 60mph at the top, I would be going about 45mph by the bottom(Not kidding) Like I said, I could understand the overrun sprag/clutch engage to control overspeed while coasting, but all my other vehicles would unlock and allow a bit of coasting, at least near the bottom of the hill. The vehicle rolls easily in neutral when I push it and the brakes are not dragging. Is the timing retard part of the overrun/ overspeed feature?

The truck "feels" like it is working and seems like it is being "held back" driving on a highway at 50-60mph.