Need help diagnosing a miss

[Tons of fun]

I have a 1985 m923 that has recently developed a miss ( like one cylinder is not firing) lacks power and don't want to drive it in fear of doing more damage. I would really like someone with some knowledge to please help me out I live in Albany, Oregon, I have called the local truck shops and they say it's to old most the stuff they work on is newer. I personally think it maybe a bad injector but I don't know where to start on this thing to figure that out. Any help would be much appreciated.

 

[73m819]

To check for a bad injector, loosen a injector line, if the miss gets worse, retighten the line, go to the next line, keep doing this till the miss does not change much, this is the bad injector, also if the injector is bad, change ALL 6

 

[doghead]

There are no injector lines on an NHC-250.

 

[sandcobra164]

DH,
I was just thinking the same thing. Overhead adjustment could have been set loose on the "dead" cylinder allowing the nozzle to foul and plug. My first step would involve using an infrared temperature gun and locating the cold cylinder by comparing exhaust outlet temperatures on the passenger side manifold with it running. Once I found the cold one, it'd be time to remove the valve cover and pull the offending injector. For a more complete repair, I'd pull all injectors and take them to a reputable shop. It may be hard to find one in your area but remain diligent and ask around. You more than likely have "Non Top Stop" injectors if the shop asks. Just keep that tid bit of information in mind as you ask around.

 

[WillWagner]

If you don't have anIR gun, use a spray bottle and water. Cold start idling, spray each port at the manifold, watch to see which one(s) do not dry or are slow to dry, it is normal for 1 and 6 to be the last to dry, but they usually do about the same time. the one(s) that don't dry up are your issue. Pull the valve cover, look at the adjuster nuts, if they are all there and tight, it is most likely the injector on that cylinder. could be a cam, but do the injector first. Read the sticky on overhead adjustment.