Latest Video on Engine Knock

[bigfootchiro]

Alright guys, here we go! Limped the Hoe from Palm Springs to Largo. Made it 130 miles, and this happened. Couple things to note... it would have a very difficult time locking up the torque converter, so transmission temps would go up to around 210 at times. If TC did lock up, it would misfire and stutter/shake like crazy, Cylinder 3 misfires would go through the roof, and TC would unlock for a while. Truck would literally only misfire when TC would lockup, but knock was there the entire time.

Makes it hard to believe that a rod bearing is bad. I’ve pinpointed knocks and misfires to Cylinders 3 and 8. Cylinder 8 happens at idle once throttle has been touched but once it starts it’s always there. If truck sits at idle after start up, it won’t misfire til the throttle is touched, and Cylinder 8 starts to misfire once idle is reached again. Cylinder 3 misfires mostly when TC is locked up.

Without tearing into the bottom side of the motor yet, what electrical issue could cause this? Bad ground, knock sensor, etc? I replaced the PCM and that did nothing.

 

[dubyagee01]

Sounds like a spark to a cylinder has dropped out. Power is down and the ecm is freaking out. Worst case scenario is the torque converter has detonated but the code says otherwise.

I would do a complete tune up and do a compression test while doing it.

 

[Tonyrodz]

Damn that sux! I hope you get it straightened out. What happened at the end of the video? Stalled and died? Or did you shut it down?

 

[bigfootchiro]

Sounds like a spark to a cylinder has dropped out. Power is down and the ecm is freaking out. Worst case scenario is the torque converter has detonated but the code says otherwise.

I would do a complete tune up and do a compression test while doing it.

I keep leaning back to spark knock too. How would the TC blowing up cause a cylinder 3 misfire? Truck has new cap and rotor, plug wires, I’ve swapped out plugs...

Damn that sux! I hope you get it straightened out. What happened at the end of the video? Stalled and died? Or did you shut it down?

It just stalled and died! I let it sit for ten minutes, and it started right up too

 

[PG01]

Seems electrical to me...

 

[bigfootchiro]

Seems electrical to me...

That’s what I keep thinking! But wtf would it be?! Maybe my cap/rotor is fried after only a few hundred miles of use? Bad ground? If it were the coil, all cylinders would misfire, am I correct?

 

[east302]

What codes are you getting?

I’ll give you credit, you would have heard me cussing if that was me in the video.


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[bigfootchiro]

What codes are you getting?

I’ll give you credit, you would have heard me cussing if that was me in the video.


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Hahaha trust me, I was monitoring the trans temps the whole way, and finally when the TC would lockup and the temps start going down, I’d hit a damn red light and would cuss my head off lol. Only codes I were getting during this time were misfire codes and EGR code (I blocked off EGR, but didn’t tune it out). I now have the EGR hooked back up, no code, and still the same is happening. I have two wheel speed sensor codes, but those have been there since the beginning.

 

[east302]

Taking a guess, you said the TC was not locking up. Does it have to be in closed loop to lock up? What does your scanner give for the coolant temperature (ECT sensor by the thermostat)?

It wouldn’t hurt to spray the ignition system down with some water at night. If it’s only misfiring on 3 and 8, maybe swap those plugs for another cylinder. Check for spark quality and compression as well.

What brand distributor cap are you using?


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[bigfootchiro]

Taking a guess, you said the TC was not locking up. Does it have to be in closed loop to lock up? What does your scanner give for the coolant temperature (ECT sensor by the thermostat)?

It wouldn’t hurt to spray the ignition system down with some water at night. If it’s only misfiring on 3 and 8, maybe swap those plugs for another cylinder. Check for spark quality and compression as well.

What brand distributor cap are you using?


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Swapped plugs around and wires, and misfires stayed on 3 and 8. Idk about the TC being in closed loop or not, but I can check ECT temps on scanner. Coolant temps on dash stayed normal the whole time, and it happens throughout all engine coolant temps.

I can’t remember the name, but it came with my Skip White performance distributor (which is not installed).

 

[bigfootchiro]

Going over the grounds, I can’t seem to find G110 on the rear passenger side of the head... is it supposed to be there?

 

[east302]

I think this is it. It’s at the back, just to the right of the transmission dipstick tube.

Edit: guess I should thank you. It looks like my coil wire’s insulation has somehow melted with an adjacent plug wire. I wouldn’t have known if I didn’t take that picture.


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[east302]

Forgot to ask, have you checked the spark on 3 and 8 with a tester? Maybe consider swapping the cap with a Delco part. I had an off-brand cap fail after 3,000 miles that gave me weak spark on three cylinders and a no-start.


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[bigfootchiro]

I think this is it. It’s at the back, just to the right of the transmission dipstick tube.

Edit: guess I should thank you. It looks like my coil wire’s insulation has somehow melted with an adjacent plug wire. I wouldn’t have known if I didn’t take that picture.



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Yes that’s the one! How many ground wires do you have on there? The schematic shows 2 grounds, plus a grounding strap. I only have 1 ground and a grounding strap.

How did that happen? That’s crazy that they melted together. Could have been a disaster down the road! Glad you found it.

Forgot to ask, have you checked the spark on 3 and 8 with a tester? Maybe consider swapping the cap with a Delco part. I had an off-brand cap fail after 3,000 miles that gave me weak spark on three cylinders and a no-start.


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I have a spark tester somewhere that I can use. I just got done swapping out for the old cap and rotor, and still same symptoms. I’m seeing that my from cap screw doesn’t hold well, due to the screw base being cracked (still secure enough), but symptoms still occur even when I hold down the cap by hand.

 

[east302]

Mine (1998, 350) has one ground wire (coming from the bulk harness) and a strap that goes down toward the frame and into a metal shield looking thing.

Wow, what a crappy location to access, lol.

As for the wires, I must have nicked one when I did the intake gaskets and it melted into the other one. But it runs just fine, knock on wood. Guess I’ll replace them.




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[bigfootchiro]

Mine (1998, 350) has one ground wire (coming from the bulk harness) and a strap that goes down toward the frame and into a metal shield looking thing.

Wow, what a crappy location to access, lol.




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I know I’m not missing a ground then. Thank you! I really is a pain in the ass. Best to use a 14mm wrench on the closed end, or you can slip in a socket, just difficult lol.

I’ll try and check spark in the morning. Can a worm distributor gear cause any of this? I’m starting to be at a loss here, and just about to throw in the towel.