I've been dealing with this issue for more than a couple years now. My 1997 k1500 silverado is occasionally gutless, but not always, and to varying degrees. I have an Innovate LM2 that is capable of displaying sensor readings in real time. When the motor is running decent, the advance at WOT is in the neighborhood of 25 degrees. When it is running like a dog, the timing is in the low teens or single digits under identical circumstances. When I start it, and it is running good, it will stay with the strong advance curve until I shut the truck off. Then I could start it up a few minutes later and it will be back to having almost no ignition advance.
It shows no codes.
The timing chain and distributor gear were replaced when I did intake gaskets on it a few years ago. I actually pulled the motor at that time to do rods and mains as preventative maintenance. I did mark the dizzy housing to block relationship at that time, and when it showed no codes after putting it back together I figured it was pretty close. I took it to the dealer anyway to have them double check the dizzy position, and they did adjust it somewhat.
I can only assume that it is a sensor that is telling the pcm to pull timing. I replaced the knock sensor, because that seemed the most obvious. There was no change.
This whole situation is very frustrating. The truck is my tow pig most of the summer, and it does great for what it is when it has full timing. When it doesn't, it's a horrible dog and I end up beating the sh*t out of the transmission.
This is definitely a timing issue, or another issue that is causing the pcm to pull timing. It is not fuel pressure related. I know of issue with the spider and poppets that people have, but I can't draw any lines back to the occasional low timing.
Thanks for reading that. I'm all ears if you have a suggestion.
Jared
It shows no codes.
The timing chain and distributor gear were replaced when I did intake gaskets on it a few years ago. I actually pulled the motor at that time to do rods and mains as preventative maintenance. I did mark the dizzy housing to block relationship at that time, and when it showed no codes after putting it back together I figured it was pretty close. I took it to the dealer anyway to have them double check the dizzy position, and they did adjust it somewhat.
I can only assume that it is a sensor that is telling the pcm to pull timing. I replaced the knock sensor, because that seemed the most obvious. There was no change.
This whole situation is very frustrating. The truck is my tow pig most of the summer, and it does great for what it is when it has full timing. When it doesn't, it's a horrible dog and I end up beating the sh*t out of the transmission.
This is definitely a timing issue, or another issue that is causing the pcm to pull timing. It is not fuel pressure related. I know of issue with the spider and poppets that people have, but I can't draw any lines back to the occasional low timing.
Thanks for reading that. I'm all ears if you have a suggestion.
Jared
