A few thoughts about you problem and process. Consider that you have been working on this for 3 years. Some of these problems can be tough but not 3 years tough. The more elusive problems take a little more time but measured in days not years. The way to get to the bottom of issues like this is a systematic method of diagnostics where things are ruled out one at a time In a logical flow until you either find and fix the problem or Confirm that function and move to the next item. It will take longer with this rather inefficient process but if we were working on this in person it would be hours or a couple of days at most. You have to make a plan and then stay focused.

Les got you set up With scanning capability and taught you how to fix your ignition timing and then he gave you a plan for exhaust restriction. You also asked about using your new scanner for other checks and measurements. Yes you can do a lot with live data, there is a huge list and Les gave you his first suggestion - fuel trims.

i am going to help you with the ignition circuit because electrical is my thing but we need to stick with it until we we fix your ignition.

I know your frustrated, I would be too but your approach has not worked, you came here for help and there are decades of experience here that can help you. Let’s get focused and get your truck fixed but let’s stop swapping parts and get to work diagnosis and repairing your problem.


George

 

I swapped the coil. No CEL light and the truck does 100km no problem. Thanks for the diagram. I'll use the diagram to check the wiring.

 

Good luck. Let me know if you need any help with your diagnosis.


George

 

There is a white wire going to the ICM ...IGN TIMMING SIG on the diagram. It's the only wire I'm not sure how its supposed to be tested ? Do I test it with led test light like i did for the TACH SIG ?

 

The truck runs so any test light or meter on AC scale will show pulses on both the signal wires so that does not tell you anything. What you looking for is anything marginal, something that might act up with heat or vibration. The first thing is clean power and grounds. Next is low resistance signal wire continuity and no shorts to power or ground (partial or otherwise). If you had a scope the last would be clean signals at the proper voltages on both signal wires. All of this is best checked when it runs crappy. So:

1) ICM pink wire: Is it within a few tenths of Batt +V, stays stable while wiggling harnesses
2) Coil pink wire: "
3) ICM Blk/wht ground: Harness disconnected measure resistance from connector to batt gnd, is it less than 1 ohm? Wiggle harnesses
4) ICM to coil wht/blk: both connectors disconnected measure resistance. Is it less than 1 ohm. wiggle harnesses. Test wire to gnd, is it infinite resistance? Test light or voltmeter from the wire to ground, does it stay off/read zero volts?
5) ICM white to PCM: disconnect both harnesses, measure resistance. Is it less than 1 ohm? Wiggle harnesses. Test wire to gnd, is it infinite resistance? Test light or voltmeter from the wire to ground, does it stay off/read zero volts?
6) Resistance of the coil lead and all 6 ignition wires.


George

 

Another way to check 4) is everything hooked up, key on and measure the voltage of the ICM ground wire back probed in the connector to battery ground.


George

 

Please humor me..........

 

Sorry I haven't been able to get back to you Guys I've been super busy. I checked the wiring and everything looks good. Now today I noticed that the oring that's in my duct work that connects to the top of the throttle body is basically all gone. Which means that my air fuel mixture is gonna be off honorably. Does anyone know where I could find one or something to put in its place ? Anyone know what the size is of the original oring ?