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Haakfarm · 11-17-2016, **(Subject: ISX chugging )**

I have a 2003 ISX, that when it is under a load and shifts gears (it is a auto shift) it chugs until you hammer down on the fuel petal. It does it more in cool air than in warm air. It does run rough when it is idling. It has about 720000 miles on it. The engine is all original as far as I know.
Has anybody experience this and what is the fix? Thanks For any thoughts.

Wiseman · 11-17-2016, **(Subject: ISX chugging )**

It could be caused by valves to tight.
How about overhead . When was the last time somebody performed valve adjustment?
Also is very good to perform injector leak test at the same time. If this doesn't help we'll go further.
Seems is time for complete tuneup!

Isn't a bad idea to pull some info from computer and post it here , so we get better idea what's going on.

Mr Hagg · 11-17-2016, **(Subject: ISX chugging )**

Sounds like a weak injector to me. I would do cylinder cut out to find weak injector also do bubble test.

Haakfarm · 11-17-2016, **(Subject: ISX chugging )**

The truck has been in 2 shops for this. Every time I get it back it seems to be better for a while and than back to the same old thing. The valves were adjusted and one injector was replaced in one shop.

Rawze · 11-18-2016, **(Subject: ISX chugging )**

It could also be old, weak intake and exhaust pressure sensors. Replace old sensors, they only usually read correctly for about 400k miles max on those engines and then throw everything off.

Also check the fuel system components and metering/timing actuators. they wear out too.

At 720k miles,. it could be simply your head is worn out. Check exhaust valve stem height while you are at it.

http://rawze.com/forums/showthread.php?t...66#pid9466