I’ve found, particularly with the isb’s, if there are cylinder misfires starting with a high count on #6 then the counts which each other decreases, example #6 30counts, #5 20counts, #4 10counts, it’s from the EGPS sensing tube becoming clogged. I’m assuming it’s because the exhaust pulses at the rear of the engine are not as strong as the first three which is why they show up first.
Thanks for sharing Joe. Totally agree, I only use and recommend genuine sensor across the board for any repair I do. I understand why some folks had to use aftermarket because this sensor was on backorder for awhile couple years back. I have been experimenting with a strategy using piezo style pulse sensor with my Picoscope to isolate misfires. I have found with an adapter in DOC inlet temp probe port (Cummins sells adapter) and section silicone hose I can actually confirm a misfire (manifold readings were two noisy to interpret for me). The pulse is quite interesting to view and it is a series of pulses as valve opens then changes as piston continues its downward stroke then changes as piston starts upward travel. Natural piston speed accel/decel, other cylinders firing, and ECM compensation all have to be considered but once you spot one that doesn't look like the others and you set up some engine phase rulers and chart it on a piston valve relationship chart you can identify the suspect cylinder. It seems Cummins used to work with Scania in the past a lot on some research and I found an excellent degree project paper on the web that covers misfire detection with EBP sensor strategy by BJÖRN NYBÄCK called Exhaust Pressure based misfire detection.
Thank you for that information. I never would have tried checking at the DOC inlet- good thinking. I will look for that paper sounds like an interesting read. Appreciate all the tips you share with the channel. We never know when something we share will help someone out of a pinch.
