N14 celect plus erratic idle

[Luckyjayb]

Just did head gaskets and replaced all 6 injectors on a n14 celect plus. Ram the rack and all set to specs. When at idle, it has a erratic idle that varies from 650-800 rpm’s. Rom is set at 700 via insite. When doing the cutout test via insite, it’s a smooth idle but stop the test and it goes back to being erratic. Everything seems to check out perfect on all the tests. Fuel pressure is where is should be per Cummins specs. I’m at a loss of what could be causing it. Any ideas or pointers on what to check would be greatly appreciated. The only live data that’s throwing me a curve ball is the ambient air pressure in right but ambient air temp is staying a constant 40 degrees.

[Signature620]

Was it running like that before?

[Luckyjayb]

(08-27-2022 )Signature620 Wrote:  Was it running like that before?

Was running smooth at 700rpms before. It just happened when I did the head gaskets and swapped the injectors for new reman ones.

[Signature620]

Try disconnecting 1 at a time at the plugs on the side of the rocker housings. They never play up on a cut-out test. It's like the ECM goes into a really focused state when you start the test.

[Luckyjayb]

(08-27-2022 )Signature620 Wrote:  Try disconnecting 1 at a time at the plugs on the side of the rocker housings. They never play up on a cut-out test. It's like the ECM goes into a really focused state when you start the test.

Did it both ways and all check out fine. I forgot to mention out of the 6, 4 were bad straight out of the box so I had to get two replaced. The main thing perplexes me is when I click on start to initiate the standard cut out test, the idle clears up and runs smooth as a bell. It runs smooth at 900 rpm’s and up. While look at live data, the ambient air pressure it correct but ambient air temp is stuck at 40 degrees Fahrenheit. I can’t for the life of me remember is the ambient air pressure sensor reads air temp as well bc if so, that could be my issue…..possibly. Thinking it’s in a colder temp than it really is. Intake temp is spot on as well. New coolant temp sensor and gauge, manual and the electric sensor, and both are reading correctly. Changed the fuel filter. I’ve done every trouble shooting step I can think out and even did all the Cummins troubleshooting steps and still no luck. The fuel pump was new when I did the out of frame on it 19k miles ago. Static timing is spot on for the CPL. Head gasket failure was due to the Birmingham Cummins dealer saying they couldn’t get the head gaskets and I had to use PAI, never will do that again, but other than that there hasn’t been an issue. Crossover tubes are good and sealed and no air getting in the system.

[Rawze]

Sounds to me like it could bad injectors, leaking into the cylinders?. When they do, it causes it to rev up a bit on its own, rpm to become unstable.

Watch the live fuel flow in Insite and see if it is going to 0 fueling when it revs up on its own. If it is, then it is a leaky injector giving it fuel when it is not supposed to.

It may or may not have been something done wrong when you worked on it but also...

-= N14 == Mostly there are only crappy injectors that have been remanned to death are running around out there for them. -= It would not surprise me if your reman injectors are leaky and causing issues. I have seen people go thru 2 dozen sometimes just to get a good set of 6.

That engine is no longer supported and the engine maker is no longer making new stock parts for them. -= One of the many reasons that I would never own one these days.

just some thoughts.

[schISM]

The 40 degrees fahrenheit sounds like a default value the ecm will use if it’s not receiving a signal from the sensor. The fact that it straightens out when you activate the cylinder cut out test would lead me to believe the issue wouldn’t be hard parts but maybe the sensor for ambient or the wire loom to the sensor was damaged during the recent work you performed. I’d trouble shoot the ambient temp. circuit till you get a correct reading and see if that helps....either way it couldn’t hurt.

[Luckyjayb]

(08-28-2022 )schISM Wrote:  The 40 degrees fahrenheit sounds like a default value the ecm will use if it’s not receiving a signal from the sensor. The fact that it straightens out when you activate the cylinder cut out test would lead me to believe the issue wouldn’t be hard parts but maybe the sensor for ambient or the wire loom to the sensor was damaged during the recent work you performed. I’d trouble shoot the ambient temp. circuit till you get a correct reading and see if that helps....either way it couldn’t hurt.

I’m getting the correct ambient air pressure though

[SemiSweet]

I had one hunt at idle and the ambient pressure sensor was the issue. But didn’t move as much rpm as your stating. It was at a default pressure which didn’t change even when unplugging. Not sure if yours is the updated sensor which is much smaller and just zip ties to the harness instead of mounting on a bracket to the block to the right of the ecm. The wiring on those n14s can be terrible as well. Did you check or replace all the injector pass trough connectors and verify the harness plugs were not stretched out causing intermittent connection.