91 N14 Cummins intermittent miss

I have seen weak or broken injector pass-through connectors, or the short pigtail harness at the top of the injectors cause this. The pass-throughs typically get skipped when replacing a harness.

 

I know this will probably hurt a few folks feelings!!! The N14 is plagued with this very problem......among other things!

 

Hmmmm... Thanks for that tip, have had one come in for the same issue

 

I have never had the pass thru cause problems,but certainly worth a look.it has always been injectors with ours.with the intermittent ones it is extremely difficult to pinpoint though.if I have an intermittent one,the only way I have been able to find it is checking manifold temps with an infared handheld.I check them on start up,then continue as it warms up,and then check when engine has been working and note the differences.usually will show up as a slightly warmer or cooler at some or all the checks.then I replace that injector but keep the one I removed for awhile to switch if it wasn't the correct one.

 

The pass throughs are only plastic. Plastic gets hard and brittle over the course of time. Connector lock tabs break/become weak and cause intermittent connections. The electrical connection becomes so deteriorated that the ECM cannot detect an open circuit, but the current is too low to properly fire the solenoids when under higher duty cycles when the engine is under more load. Remember, this engine is over 20 years old!

 

I agree with you heavyd,just haven't personally seen them fail.I've had the lock tabs broken before though.usually see code for weak connections,but with electrical there is no guarantee they will give code.could also have ECM read and see if there are any discrepancy in voltages for injectors,may at least point ya to the right cylinder.

 

Sounds like you have injector sleeves that are worn.Most of the sleeves are copper and when they start to wear you get a miss under load or hard pull some times. Just had one in the shop with same problem.