Alright guys I am experiencing a miss at all RPMs. It is pretty noticeable near the engine with a knock, but is extremely noticeable at the exhaust. It is easy to feel that the exhaust is "puffing" per say. Now I just replaced the injectors with a new set of 125hp sacs, but the miss was prevalent before the injector swap. The swap did not make a difference. Everything sounds the exact same as before the swap. I have fuel squirting out of each connection at the cross over tubes while running.

MoparMan and I spoke on the phone earlier and have decided to take a systematic approach to resolving this issue.

Ruled out: 1. Injection pump: Always supplied good pressure, less that 10K miles and miss seems to only be in one cylinder. 2. Injectors: Swap made no difference.

Possibilities (Almost endless): Burnt/ broken valve, broken piston or piston rings, clogged cross over tube, valves way out of adjustment

 

I should receive the truck Friday from being painted and I can start diagnostics. 

The plan: 1: Pull valve cover and quickly check valve lash - just make sure somewhat close to spec. 2. Use an infrared heat gun on the exhaust manifold right were it come out of the head to try and narrow down which cylinder is missing. If that does work I will pull the cross over tube and replace it (I already have 1 new one that will ship out Monday). If that does not fix the issue I will do a compression test on that cylinder to determine if it is the bottom end or the head.

If the heat gun does not find a "cold" cylinder I will pull all injection lines and cross over tubes, then clean each tube and try to determine if there is debris in one of them. If I can not find debris in any of them I will replace them with the new one, one at a time. If that proves inconclusive I will perform a compression test on all 6 cylinders. 

If any of the cylinders are low on compression I will pull the head and determine what is wrong internally.

 

Any suggestions on the procedure or something else I can do to diagnose what is wrong with this thing??

Edited October 26, 201410 yr by TFaoro

Come to Idaho you can listen all you want...

Come to Idaho you can listen all you want...

   I'm pretty sure there is  at least  1  'good running'  24v    in the  Denver area..   might   be   a  tad closer!

Might have to buy Nick a couple beers to let me listen to his 

 

Come to Idaho you can listen all you want...

I wish there was something high quality enough to capture the sound! I know your's sounds like a champ! Just can't quite afford the drive 

I was talking on the phone to another gent and mention your issue and he suggested doing the Blue Chip hot wire trick and see if the ECM is creating this issue maybe? Because this would be just the VP44 by itself no other computer or electronics to fool with it.

I was talking on the phone to another gent and mention your issue and he suggested doing the Blue Chip hot wire trick and see if the ECM is creating this issue maybe? Because this would be just the VP44 by itself no other computer or electronics to fool with it.

Thank you for the suggestion! But I have already done it.... No change when hotwired.

Still hunt for solution or test so I'll keep asking around too.

Still hunt for solution or test so I'll keep asking around too.

Thanks Mike. We'll get it figured out eventually!

Tyler, did you actually check for a worn cam lobe?

I'm thinking slight bent connecting rod. Not getting enough compression, it's still firing, but not as strong as the rest, makes it seem like a miss.

He did compression & leakdown tests. I would think that a bent rod would show there.

 

Ed

Tyler, did you actually check for a worn cam lobe?

Will be doing that in a couple of hours 

I guess you going to measure the lift of each push rod correct?

He must be taking his time.........

I'm too lazy to   read back through  12 pages  of this  thread..     did he ever  check  his  pushrods being  bent?  

Yes he has.

 

Ed

Sorry guys got stuck at work on hold for an hour    then had to stay another hour to figure out timecard problems. By then it was dark. Thursday is my next chance with some free time! My plan was to check the lift of each pushrod. 

I can send my dial indicator to ya. I think it has the magnetic mase, too. Let me know & I'll call Mercury to make another trip...

Ed

I can send my dial indicator to ya. I think it has the magnetic mase, too. Let me know & I'll call Mercury to make another trip...

Ed

Thanks Ed! I am going to start with a tape measure, and if any of them seem "different" than the rest I will be giving you a call.

I'm going to bump this back up and pick your guys's brains a bit.

I put the drilled out crossover tubes back in just to see if it would change anything (The last time I only had them in for a day or so)

Well it seems to have amplified the "miss" making it 3 or 4 times worse. Now it's REALLY noticeable. Wouldn't that mean it's something to do with fuel delivery if only crossover tubes made it this much worse?

That makes me want to think there is a fuel deliery issue somewhere, but are you hearing a miss or are you hearing a lope? From what I have heard about the only thing the drilled cross over tubes do is cause a bit of a lope.