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Dead Lifter...Maybe! (update)

1-ton

1-ton

3/4 ton status
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My new GM crate engine with about 5000 miles on it developed what sounds like a valve train noise. I started the truck up a few days ago, and it started to misfire real bad. I opened the hood , and removed the air cleaner lid. I could see that one of the TBI injectors was not firing at all. I pushed down on the TBI electrical connector, and it started firing the injector. My truck was running normally after that, but when I started to drive down the street at about 2000 RPM I heard what sounded like a loud valve train rattle.

I turned around and went back to my house. I opened the hood again, and grabbed the throttle lever by hand. I revved the engine up to about 2000 RPM, and could not hear any valve train noise. I then drove down the street, and heard the same valve train noise again. Apparently the valve train noise will only happen when the engine is under load. Then I grabbed my stethoscope, and listened to every part of the engine there is. I could not hear anything. So, I parked my truck and called it a day.

I had to go to work the next morning, and I drove my truck. The truck started to make the valve train noise again, but this time it started to develop a bad miss fire.

These are the tests I have done so far to try to diagnose this problem.

1. Stethoscope, no noise found
2. Remove valve covers and inspect (no loose rocker arms or cracked valve springs)
3. Remove all spark plugs (all plugs look normal)
4. Compression test (all cylinders check out at 145 PSI with no leakage of pressure)

I do not expect any replies will help this problem because it is one of those problems that you have to be there to get any understanding of what is going on.
 
Any chance the noise could be a rattle coming from an external part that’s loose or rubbing something?

Just thinking they’re not related, the miss is the tb connector and (hopefully) the rattle isn’t internal.
 
nvrenuf said:
Any chance the noise could be a rattle coming from an external part that’s loose or rubbing something?

Just thinking they’re not related, the miss is the tb connector and (hopefully) the rattle isn’t internal.
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I was hoping I could get lucky, and would be something like that. It is curious how the whole thing started immediately after a miss fire from a TBI injector. It would seem that the TBI injector problem would have to have be related some how to what is going on with my engine because it never had a problem before the injector mishap.
 
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I'm not of much help on computer controlled / fuel injected engines--but I see some weird stuff happen to vehicles at my friends shop and hear about some unusual failures from other mechanics..

Could it be the computer tried to compensate for the non working injector by adjusting the fuel mixture or altering the timing ?..either of those could cause pinging or pre-ignition...the plugs wouldn't show any damage right away from that..

Perhaps its just a fluke this noise started after the injector acted up--perhaps the torque converter bolts loosened up,or the flex plate has cracked ?--loose muffler baffle or cat converter guts rattling around ?....seeing you found no broken parts and have good compression,that kind of points to it not coming from the engine probably..
I've heard engines with a hunk of carbon that broke loose make horrible sounds,and the engine was considered "junk"--once it was taken apart,they found big chunks in a few cylinders that broke free from under the heads of the intake valves...
I've also seen and heard a few engines that sounded like a bad rod bearing that were "fixed" by pouring Marvel Mystery Oil down the carb slowly,until it stalled,then let it sit a few minutes and start it back up and rev the snot out of it--after the smoke cleared,no more scary noises!..black soot came out the exhaust..
 
Sure it's not an exhaust leak? Those are famous for only rearing their ugly head under load...
 
I agree with the noise being possibly related to a misfire from either bad injector, incorrect timing, loose distributor, bad ICM, coil, bad pickup coil, (related to injector firing), burnt wires etc. Maybe the one injector stops working while driving due to vibration? Any engine codes? Checked oil level? I would go through all the regular tune up items/ignition one by one and see if you find anything. Did you put an old, high mileage distributor in the new motor? It’s just suspicious that this happened after a misfire. The engine misfiring badly may cause the noise. If it only makes that noise when that injector is not firing, then that’s your problem. Just need to find out why that injector is intermittent. Keep us posted what you find.
 
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89 jimmy said:
I agree with the noise being possibly related to a misfire from either bad injector, incorrect timing, loose distributor, bad ICM, coil, bad pickup coil, (related to injector firing), burnt wires etc. Maybe the one injector stops working while driving due to vibration? Any engine codes? Checked oil level? I would go through all the regular tune up items/ignition one by one and see if you find anything. Did you put an old, high mileage distributor in the new motor? It’s just suspicious that this happened after a misfire. The engine misfiring badly may cause the noise. If it only makes that noise when that injector is not firing, then that’s your problem. Just need to find out why that injector is intermittent. Keep us posted what you find.
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I am going to go in that direction before I start tearing things down too far. I was talking to a couple of guys I work with that have been mechanics for close to 50-years, and they think my trucks problem may be an injector not functioning properly; thus causing pre-ignition which is the valve train noise and misfiring I am getting.
 
My TBI currently has a set of matched injectors that were rebuilt by Vic Morse back when I put this new engine in (along with the entire TBI being rebuilt, bored out, rebushed throttle shaft, and ultimate modified). I am going to replace the TBI injector connector that came loose first to see if that is the problem. I put a new set of injector electrical connectors in it when I installed the new engine, but one of them seems to have gone bad already. If the connector does not solve the problem then I will look into the injector itself as the potential problem.

full
 
Fastereddie said:
LS swap. Haha! Had to do it!
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An 8.1Liter Big Block would be bad ass, but there would be a lot of work that would have to go into the modifications of ECM controls for my over-drive trans and 8.1L engine. With the set-up I have now I am able to use all the ECM controls it came with from the factory.
 
It really sounds like a lean "labor knock". I'm betting that that wonky injector is the problem. When its working normally, all is well. As it begans to fail, it gets intermittent and the engine starts running lean and knocking, but not bad enough to actually run rough.
Then the injector fails completely and it starts running really rough.
Kind of an off the wall idea, but did you replace the motor mounts when you replaced the engine? Poor mounts would let the motor twist under load and move a bad or loose wire and only let it happen when driving.
 
Fordum said:
It really sounds like a lean "labor knock". I'm betting that that wonky injector is the problem. When its working normally, all is well. As it begans to fail, it gets intermittent and the engine starts running lean and knocking, but not bad enough to actually run rough.
Then the injector fails completely and it starts running really rough.
Kind of an off the wall idea, but did you replace the motor mounts when you replaced the engine? Poor mounts would let the motor twist under load and move a bad or loose wire and only let it happen when driving.
Click to expand...

Yes, I did replace the motor mounts when I installed the engine. If the injector is bad, I will probably go with a set of those AC/Delco injectors that 89jimmy posted, and then send the set I have back to Vic Morse to be rebuilt and matched again.
 
I put my engine back together, and replaced the TBI injector electrical connector that went bad. I visually inspected my TBI injectors with the hood open, the air cleaner lid off, and the engine running. It looks like they are working good. My truck is running OK, but it is still making a rattle sound only under load at about 2000 RPM. I had a friend of mine stand beside my truck with the hood open, and then I power-braked my truck up to 2000 RPM so that he could hear where the noise was coming from. He said it sounded like the noise was coming from the alternator, which is what I was suspecting.

My truck still miss-fires a small amount, but it runs and idles real strong. I think the mis-fire is ignition related. I still have the cheap Chines distributor cap and rotor the Jegs in-house billitt distributor came with. before I installed that distributor I did replace the cheap Chines pick-up coil and control module with AC/Delco stuff. Plugs and wires are all new good quality parts too.
 
I saved the AC Delco boxes for most of the parts I replaced recently. The AC Delco professional line of parts is either USA or Mexico. I did not see any made in China. My MAP sensor and new injectors are made in USA! :waytogo:
 
The BOX was made in the USA...:D...
The parts ,who knows where ?..my guess is where ever the cheapest bidder was..:surepal:
 
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