N14 miss

I got a buddy who came by this afternoon to unload some equipment. Had me listen to a noise in his engine. Sounds like the engine is labouring/stumbling a bit at random. Says it does it under light load conditions. Said he had all 6 injectors and the pass through connectors replaced and it made no difference. I heard it act up for several seconds at a time. Not really a miss per se, more like a change in tone to a rougher idle. Dealer told him it sounds like a head but he said they never did any testing to verify it. Very intermittent so I can't see it being a head.

Truck's an early 2003 T800 with N14. Unfortunately I have no access to computer or any diagnostic equipment at this time. Any suggestions on things a guy can check without needing access to insite?

 

I'll definitely pass those suggestions along. I'm only down visiting for the weekend so I don't have any tools or anything to do any kind of digging.

He didn't have any complaints about it lacking power. Just sitting idling I heard it act up once or twice for a couple seconds each time. It basically just sounds like its running a bit rough, then clears up. It will do it at high idle and if he's under light throttle on the highway he mentioned. Under hard pull he says he can't feel anything out of the ordinary.

 

Wouldn't a fuel issue be more prominent under full load though since that'd be when you've got the most demand for fuel? Unless he's got an issue with an injector not firing correctly at random, so the other 5 are temporarily putting out more fuel to keep it running? I've never worked on an N14 so I have no clue about anything specific on them.

My first thought was maybe it was the compressor cutting in as the noise sounds similar to a compressor working, only louder than what I remember. However the dryer only purged once after he reconnected the neck and charged the trailer. I would think if the compressor was cutting in it would purge the dryer each time?

 

You know, he shut the truck off while waiting to find out where they wanted him to unload and I do recall it taking a little longer than what I would consider normal for a warm, electronic engine to fire. Same with when he started up the truck to reattach the neck after unloading. Probably cranked for about 4-6 seconds. First time truck was off for less than 3 minutes, 2nd time it wasn't off any more than 15 minutes.