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OK, if you've followed my Project Resurrection thread, you've seen my issues with the engine. I'm at a loss so I figured I would start a thread in this forum to start figuring out how to troubleshoot the issue.

I'll try to create a video with the audio of what's going on but I don't have that just yet. I'll post it when I have it.

Long story short, all signs point to detonation in the exhaust. It does this almost immediately after starting the car. I say detonation in the exhaust because I had a buddy check it out with me and he indicated that it was detonation in the exhaust.

Here is a short list of what I've checked/changed:
  • Ignition System
  • Timing
  • Fuel Pressure
  • Vacuum Leaks (as best as I could)
  • Exhaust Leaks
  • Pulled Codes (No codes)
  • Re-flashed Chip
  • Wiring
I'm open to any other ideas.
 

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Detonation in the exhaust Immediately after Starting it would have to mean at least one cylinder is firing with an exhaust valve open, and unburned fuel is in the exhaust.

If it does it after the exhaust is hot, then it can be too much fuel, maybe a stuck injector.



Can you tell if it's one cylinder, on both sides, or randomly in both sides?

Adding a meter across an injector, and shining the timing light hooked to that cylinder could show this; the injector has to fire, then the spark, and the crank needs to be in the right spot.
If you can get an led across the injector and shine it on the crank wheel, you could see how many degrees apart they are, and where it's timing.
Search this: MSD Ignition Timing Tapes for Harmonic Balancers
These are tapes that stick to the harmonic balancer, and show the timing.

A boom in the exhaust is going to be after TDC; it should be before. Max on my car is set to about 20 degrees before, iirc.

A consistent ignition in the exhaust is going to be the timing is off, somehow.

A random firing is going to probably be noise pickup in the sensor wiring; or maybe a bad pickup in the distributor. (maybe a spark plug wire is too close to a sensor wire, or a spark leak in the distributor?)
Spark leaking in the distributor should leave a track, a darkened area like a line drawn with a pencil.
If the cap is dirty, you can wash it out with rubbing alcohol, or starting fluid.

One side only could be a stuck valve, and it's open when the cylinder fires. But where's the gas coming from, if there's no timing problem?
And you usually hear valve problems, when the piston smacks it.

That's everything I can think of; I hope it helps. :)
 

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Discussion Starter #3
Detonation in the exhaust Immediately after Starting it would have to mean at least one cylinder is firing with an exhaust valve open, and unburned fuel is in the exhaust.
While I agree with this in principle, it also doesn't make sense when I think about it. I'll try to get a video/audio of it.

If it does it after the exhaust is hot, then it can be too much fuel, maybe a stuck injector.
The car has never had a chance to get hot. I have replaced all of the injectors with new ones. I don't think this is it.

Can you tell if it's one cylinder, on both sides, or randomly in both sides?
It is totally random. It sounds like it's all sides but I've been afraid to run it too long to find out for sure.

Adding a meter across an injector, and shining the timing light hooked to that cylinder could show this; the injector has to fire, then the spark, and the crank needs to be in the right spot.
If you can get an led across the injector and shine it on the crank wheel, you could see how many degrees apart they are, and where it's timing.
Search this: MSD Ignition Timing Tapes for Harmonic Balancers
These are tapes that stick to the harmonic balancer, and show the timing.
I have a balancer that has timing marks on it. I have manually set the timing and ensured it's right by using my compression tester and hand cranking the engine until I'm getting compression on #1 and it aligns to the 10 degrees BTDC and then installing the distributor per standard practice. I have run the car long enough to then use the timing light (with SPOUT removed) and set the timing at run to 10 degrees BTDC. The timing is correct for sure.

A boom in the exhaust is going to be after TDC; it should be before. Max on my car is set to about 20 degrees before, iirc.
A consistent ignition in the exhaust is going to be the timing is off, somehow.
See timing comment above.

A random firing is going to probably be noise pickup in the sensor wiring; or maybe a bad pickup in the distributor. (maybe a spark plug wire is too close to a sensor wire, or a spark leak in the distributor?)
Spark leaking in the distributor should leave a track, a darkened area like a line drawn with a pencil.
If the cap is dirty, you can wash it out with rubbing alcohol, or starting fluid.
I've been worried that this is a thing. I have swapped distributors without any change. I have re-routed the wires because I thought that maybe that was the issue but it showed nothing. I pursued the shielded wire stuff and it's all shielded and nowhere near the alternator. I have checked the cap repeatedly and there is nothing strange inside it. No odd marks, no extra dirt/dust. Just looks normal. I still feel like this is a thing however.

One side only could be a stuck valve, and it's open when the cylinder fires. But where's the gas coming from, if there's no timing problem?
And you usually hear valve problems, when the piston smacks it.
It feels like if I had a stuck valve that I would experience something more consistent. When I had a buddy listen to the car in person his assessment was that the car is running normally other than the loud pops. He's built several engines that actually run and have run for years so I trust him. He's actually the guy that got me into all of this almost 20 years ago.

That's everything I can think of; I hope it helps. :)
That does help. If nothing else it helps my sanity.

I have to admit one thing. I dreamed of it all night last night. The vacuum hose for the PCV valve to the upper intake ports is the original for the car. It's rather firm but I haven't replaced it because it's a molded hose and there is no aftermarket replacement. It's also the biggest diameter vacuum hose. If it's sucking air then it could be significant. I'll work to change that this evening but since I've tried so many other things without success I'm not getting my hopes up on this one either.
 

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Silly question, but you did change out the eec at some point, I think, right?

If you're using a chip, can you try it without it without blowing anything up?

Dang; this is too good a project for something random like this. :(

I just had to throw everything out there; I'm betting when you find it, it will be something easy; that's the way it seems to go with me, anyway.

Keep your chin up; we'll find it. :)

We need Matt; he's the Genius. :D
I'm more the village idiot, on a good day, lol.
 

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Discussion Starter #5
Silly question, but you did change out the eec at some point, I think, right?

If you're using a chip, can you try it without it without blowing anything up?

Dang; this is too good a project for something random like this. :(

I just had to throw everything out there; I'm betting when you find it, it will be something easy; that's the way it seems to go with me, anyway.

Keep your chin up; we'll find it. :)

We need Matt; he's the Genius. :D
I'm more the village idiot, on a good day, lol.
I have also swapped the ECM with no success. I could pull the chip but it would resort to running off the stock tables for 19lb. injectors and the stock MAF. It would then be super rich and I would expect the problem to be worse.
 

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I agree it would not be optimal, but at idle it might be close enough to run, and I'm just curious if it still fires in the exhaust.

I certainly wouldn't want to blip the throttle hard; it will be ~20-30% lean, but it doesn't take a bunch of gas to idle.

It will probably act like it's starving for gas, but the lack of the 'boom' would tell you a lot.

I'm just wondering if there's a way to eliminate the piggyback chip as a source for this.

EEPROM chips have been known to toggle bits when they get old. (That's why they put tape over the window on the older ones, UV light from florescent lights would erase them sitting on the bench. I've had that happen at work, years ago; that's hard to find, lol)

I'm sure you've cleaned the pins carefully, and all that stuff; but when I get wrong results, flashing back to the stock program to see if it runs is my first step.
In my case, it's usually my fault, lol.

I'm just trying to cover everything; like I said before, when you find it, it will be something easy we haven't thought of yet.

It ran perfect before the wreck; and it's really close, just with some unwanted 'features'. :)
 

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Discussion Starter #7
I agree it would not be optimal, but at idle it might be close enough to run, and I'm just curious if it still fires in the exhaust.

I certainly wouldn't want to blip the throttle hard; it will be ~20-30% lean, but it doesn't take a bunch of gas to idle.

It will probably act like it's starving for gas, but the lack of the 'boom' would tell you a lot.

I'm just wondering if there's a way to eliminate the piggyback chip as a source for this.

EEPROM chips have been known to toggle bits when they get old. (That's why they put tape over the window on the older ones, UV light from florescent lights would erase them sitting on the bench. I've had that happen at work, years ago; that's hard to find, lol)

I'm sure you've cleaned the pins carefully, and all that stuff; but when I get wrong results, flashing back to the stock program to see if it runs is my first step.
In my case, it's usually my fault, lol.

I'm just trying to cover everything; like I said before, when you find it, it will be something easy we haven't thought of yet.

It ran perfect before the wreck; and it's really close, just with some unwanted 'features'. :)
OK, more work. I did swap chips. At first I thought I fixed it but the more I observe it, the more I know that it's a problem that only exists at idle. If I give it some gas then it clears up. I'm beginning to wonder if I have a stuck injector or something. I'm also wondering if the base tables are just too rich and it's causing it because it seemed like it improved once it started to warm up a bit. I'm still confused but it's better than I was feeling. :confused::confused::confused:

Video with burned chip:
https://youtu.be/p7WRoPUXuzc

Video with Quarterhorse:
https://youtu.be/qN0HVJdAaVc

I apologize in advance for the shitty audio. Apparently my phone doesn't handle that noise all that well. You'll still get the picture of what it's doing though.
 

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I've heard that before; that's what my 750 does when the carbs need cleaning, and are dribbling gas down the pipes.

I think you're on the right track; rich, or stuck injector.

That does not sound like it's in the manifold, but lower down.

I'm guessing there's no restriction in the exhaust, so it whooshes rather than bangs. :)

Are you sure there's not a puddle of gas in the pipes?

The normal firing will blow it out, then it will pop again as air gets scavenged back into the pipe.

It's rich burning (lots of fuel to the air, when it whooshes), otherwise the pipes would ring. :)

The QH video seems to do it less; can you compare the tables?
 

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Discussion Starter #9
I've heard that before; that's what my 750 does when the carbs need cleaning, and are dribbling gas down the pipes.

I think you're on the right track; rich, or stuck injector.

That does not sound like it's in the manifold, but lower down.

I'm guessing there's no restriction in the exhaust, so it whooshes rather than bangs. :)

Are you sure there's not a puddle of gas in the pipes?

The normal firing will blow it out, then it will pop again as air gets scavenged back into the pipe.

It's rich burning (lots of fuel to the air, when it whooshes), otherwise the pipes would ring. :)

The QH video seems to do it less; can you compare the tables?
So, it's either too much fuel or unmetered air. I feel better about it now. Matt mentioned that he thinks it's unmetered air. I have two things to check. One is the thermactor ports on the back of the heads. The other is the connection at the collectors. When the engine was pulled and on a stand the plugs on the thermactor ports could have loosened. The collectors have been a deteriorating connection for a while because of all of the removals. I'll work on those first.

The too much fuel thing seems less likely but I can roll back to the old injectors and see if that helps if the air fixes don't.
 

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So, it's either too much fuel or unmetered air. I feel better about it now. Matt mentioned that he thinks it's unmetered air. I have two things to check. One is the thermactor ports on the back of the heads. The other is the connection at the collectors. When the engine was pulled and on a stand the plugs on the thermactor ports could have loosened. The collectors have been a deteriorating connection for a while because of all of the removals. I'll work on those first.

The too much fuel thing seems less likely but I can roll back to the old injectors and see if that helps if the air fixes don't.
This problem could easily be air getting sucked into the collectors; all engines start rich, so I'd let her warm up and see if it goes away.

The level of 'afterfiring' isn't exhaust shattering, so I'd run it for a bit to see if it goes away, and see what the fuel trims say when it gets into closed loop.

I've heard properly running carbed cars with more exhaust pop than that. :)

Seems like some of the chevy guys add air into the exhaust just to do that, iirc.

Other than the slight pop, it sounds really good. :)

It sounds to me like it wants to add some nice rubber marks to your neighborhood, lol.


Do you have a wideband?
 

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Discussion Starter #11
This problem could easily be air getting sucked into the collectors; all engines start rich, so I'd let her warm up and see if it goes away.

The level of 'afterfiring' isn't exhaust shattering, so I'd run it for a bit to see if it goes away, and see what the fuel trims say when it gets into closed loop.

I've heard properly running carbed cars with more exhaust pop than that. :)

Seems like some of the chevy guys add air into the exhaust just to do that, iirc.

Other than the slight pop, it sounds really good. :)

It sounds to me like it wants to add some nice rubber marks to your neighborhood, lol.


Do you have a wideband?
I haven't had familiarity with a car that snapped and popped like that so it was definitely freaking me out. I also think that it's coming in around the collectors because my entire exhaust system is super tight and while I thought I was pulling things in tighter, I was probably just bending the retainer rings on that bolt the exhaust to the headers.

I do have a wideband, just not installed. I'll fix the next most obvious thing and work from there. I'll keep you updated.

Thanks again for all of the help.
 

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why are you not logging with the quarterhorse? that would tell you rather quickly whats going on
I had a burned chip in the car. I do generally have it resolved now.

I'm just in hell getting the clutch to work. I can get the throwout bearing to move about 1/2 inch which either apparently isn't enough to get the clutch to disengage or something else is wrong.

I don't want to have to remove the transmission but that may be where I am.
 

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... I can get the throwout bearing to move about 1/2 inch which either apparently isn't enough to get the clutch to disengage or something else is wrong.

...
If the clutch moves 1/2", and it doesn't disengage, something is wrong.

Most clutches I've ever dealt with move less than that.

I've ground 1/8" (average, it was ugly) off a clutch plate to keep it from disengaging.

I hate to say it, but if it really is moving that far, you gotta take it apart to look.

:frown2:
 

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If the clutch moves 1/2", and it doesn't disengage, something is wrong.

Most clutches I've ever dealt with move less than that.

I've ground 1/8" (average, it was ugly) off a clutch plate to keep it from disengaging.

I hate to say it, but if it really is moving that far, you gotta take it apart to look.

:frown2:
Before I pull it apart, what should I be looking for? I can see the clutch pushing in. Is it possible that it's out of alignment somehow? I wouldn't have thought I could get the transmission back onto the engine if it was it out of alignment somehow.
 

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My suspicion is still the new flywheel, if it’s closer to the engine than the last one the TOB will be too far to act on the fingers. I can’t think of anything else, it’s the one thing that has changed in the equation
I generally agree but I didn't see any obvious differences when I put it in.

I guess I know what I'm doing this weekend. :mad::zbash:
 

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The clutch only has to move 1/4" to let go; it needs to compress the springs, and clear the surface.

You're moving 1/2"; that should be way clear.

You're going to have to look.

Are you SURE it's moving that far?

If it's not, I could see it; but at that level of travel, you should have nothing.
 

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The clutch only has to move 1/4" to let go; it needs to compress the springs, and clear the surface.

You're moving 1/2"; that should be way clear.

You're going to have to look.

Are you SURE it's moving that far?

If it's not, I could see it; but at that level of travel, you should have nothing.
It's definitely moving that far.

I found a post here that may well be the problem: https://www.explorerforum.com/forums/index.php?threads/problem-with-5-0-manual-m5r2-swap-clutch-wont-disengage.444364/

In my effort to get pressure plate bolts that are appropriate, I may have ones that are just a bit too long. I'll inspect that this weekend too.
 

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It's definitely moving that far.

I found a post here that may well be the problem: https://www.explorerforum.com/forums/index.php?threads/problem-with-5-0-manual-m5r2-swap-clutch-wont-disengage.444364/

In my effort to get pressure plate bolts that are appropriate, I may have ones that are just a bit too long. I'll inspect that this weekend too.
Use markup fluid, like prussian blue, to mark everything before you put it back together; that way, you will have marks inside that show you what's wrong, IF you have to take it apart again.

That sux; I've never tried to piece together parts from different stuff to make them work, as far a s clutches are concerned.

Well, manual ones, lol.
 
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