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Super Moderator
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3,188 Posts
Discussion Starter #1
This is a message I got, but need Cat guys to help:
HELP!! 3406A cat... runs great cold and at idle or accelerating... once engine warms up if you try to hold a steady speed it misses so bad it feels like u-joints will give. Have spent thousands on this truck and no luck finding problem.. All nozels have been replaced twice (first time was aftermarket .. 2nd time cat parts) .. not sure what to look at next.. this truck was supposed to help us ... and is becoming more of a hinderence. Husband got laid off last year from oil field... this is the last of our $$ that went to buy this dumptruck.. we need help...
 

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Junior Member
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255 Posts
Have you guys checked the top end at all. Valves are all within spec??

Another thing i would check is fuel pressure under load.
 

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Junior Member
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40 Posts
Does it also miss when parked at mid RPM range?
Use an inferred heat gun to test temperatures at each exhaust port on the manifold.
 

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Super Moderator
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3,188 Posts
Discussion Starter #5
Thanks a bunch for the help!!
Here is their response:
Okay.. we read the feedback. Husband said he has ran overhead times. Changed all nozzles, turbo rebuilt and checked for cold cylinder. He found a new old stock governor that he is replacing today. pump was rebuilt just prior to us buying the truck. All fuel lines have been checked. He did say it has a slight miss at idle but definitely cannot hold a steady speed because of miss.
 

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Super Moderator
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3,188 Posts
Discussion Starter #6
Governor replaced with new old stock. ... No change. $2000 more on truck
 

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Junior Member
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40 Posts
Go back to fuel pressure under load. Fitting in place of plug on top of fuel filter head (base), 1/4 inch air brake tubing, fittings, and a 100 PSI or more gauge. All for under 50 dollars. Tie it on the mirror bracket. Test stuff and fix the problem, send it to someone that will, or sell it. Can you post a video of it?
 

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Senior Member
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2,555 Posts
Remove the fuel shut off solenoid and make up a dummy plate to seal the hole, tie the solenoid up so that it can't short out, road test truck, you will either need to stall it or use the mechanical shut off to kill the engine.
 

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The other guy
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3,936 Posts
First thing to find out is if it a single cylinder miss or a random slobber miss. As it doesn't do it under full load there's only a couple things it can be.
 

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idunnoyet
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231 Posts
I'm thinking Fuel Transfer pump. Check fuel pressure like mentioned above. May have enough fuel to run but not enough under load
 
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