2009 Dodge journey misfire

[dmarch]

Hi all,

I've got an 09 journey with 170km, inline 4. I bought it with a misfire thinking it would be a simple fix, as it usually is. I compression tested, came out good. I've swapped spark plugs, coil packs, fuel injector, but my cylinder 1 misfire doesn't follow anything and doesnt go away. Only code is cylinder 1 miss. It starts up fine, idles fine, but if you drive it up and down the street under heavy load (high accel) the CEL starts blinkingz indicating that it's missing. It usually feels fine at this point, if it is misfiring at that point it's quite minor. Eventually cylinder 1 just fully shuts off, constant misfire that won't stop until you turn it off, and start it back up then it runs fine. I've ripped the wiring harness apart, wires look ok. I've probed coil and injector as well, the coil seems fine, but when the misfire becomes constant the injector stops pulsing to ground. It has constant 12v, but doesn't get the ground pulse from the ECU to fire. I understand the ecu can shut off fuel if it thinks it's misfiring to avoid washing the cylinder walls with unburnt fuel, but the spark is working fine, so what other reason would the ecu decide to shut off cylinder 1? Another thought is the air going into the engine, but I find it hard to believe that cylinder 1 only wouldn't be getting enough air. Not sure how to troubleshoot this. Any help appreciated. 

Thanks

[John/Horace]

Welcome to the forum.  Intake manifold seals on cylinder 1 can allow extra air if bad and set codes. Leak down test on cylinder could be useful. Boroscope cam to look at intake valve through spark plug hole. How is upper valve train noise, clacking when it’s running?