Ok so I have ordered a new mopar crank sensor and a new PCM. I will replace both and God willing one of the 2 will also solve the ABS problem that is intermittent.

This may sound stupid......but throwing parts at it....is my most economical solution at the moment. The vehicle has 111K on it........I'm pretty blown away as to how many sensors go bad on these things.

Hk

 

The map sensor degrades over time, same with the crank sensor. I swapped both on the Ram I have which I tune with HPT and with the NGKs that I put in, immediately got a CE light. Swapped in Cummins sensors and all has been good after that. The magnet on the NGKs was weak.

On you mis-fire since engine is good when in open loop, it indicates to me that there is a sensor problem. Or... the ECM cannot read the sensor inputs. The scanner would allow you to monitor the sensors and see that they are working to a point. There are some threads on here talking about swapping the map sensor for an mpg gain. in the conversations they talk about the diaphragm getting brittle and loosing sensitivity. When I swapped mine on the 4.7 Dak engine, mpg jumped up to upper 17's, but that mpg was lost when I put in the 2 new cam/crank sensors. that told me the timing was being artificially advanced with the degraded sensors

 

RE:--Another issue is when id does shift normally it's when I'm light on the gas. Hard acceleration causes the transmission issue. I also believe the truck has stuck in 3rd some of the time.

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How is it shifting with new sensor/ pcm?
-those wont do anything if theres a issue with tranny sensors/ accumulator spring.

 

OK folks here is the update.........I'm still desperate.
New PCM and new Mopar Crank sensor.

I am beginning to unpack the issue though. From a fresh battery connect all cylinders fire. After the vehicle warms up and I stop at a light for a minute the misfire returns and the vehicle goes into limp mode which is rectified by my turning the truck on and off.

Ii I stop at a light and put it in neutral and keep the vehicle slightly rev'ed then the condition does not happen.
So is this vacuum related? If so why the 3, 5 misfire only.

Still hunting but I need the expert advice here.

HK

 

As Hey You spoke on -what plugs are you running?
Are you using OEM TPS/ IAC sensors?

 

Time to look at the upstream oxygen sensor(s) then. Those are what are actually used to track misfires. The computer monitors the timing of the spark event versus the peaks/valleys picked up by the upstream oxygen sensor. If the timings exceed certain thresholds, it will set a misfire code. If the sensors get weak, the internal heaters and/or exhaust gas heat may become such that the sensor simply can't detect the changes/pulses.

 

It would be helpful if you answer the questions "WHAT PLUGS DID YOU PUT IN? " Heat range also. From what you are describing it sound like a injector issue but could also be with the ignition. Did you put in el cheapo parts (cap/rotor wires) in or good quality stuff? I seen way to many issues with cheap parts(and good ones also). You can swap the 3 and 5 injectors into other cylinders and if the codes fallow the injectors then you found your problem. Wouldn't hurt to put some injector cleaner in the tank and drive it like you stole it and see if it clears the misfires.

 

Plugs are NGK platinum.

So drove the vehicle on a 200 mile trip yesterday. The check engine light came on shortly after driving. I also put the older transmission speed sensor back in the truck that is came with. When Pep Boys scanned the car in the beginning they said it was bad so a purchased a new (non mopar) one and put it in which is where the transmission started shifting harder.

Yesterday the transmission shifted smoothly and kicked down properly.

Also a new condition popped up yesterday...... from one moment to the next the brakes pumped themselves up and the ABS and Brake Lights when out for a moment. So when I say pumped themselves up......it almost felt like the brake booster came back to life.

This now has me thinking........ I know that if I sit at a light with the truck in gear for a few minutes......I start to get a very rough idle and this is where the limp mode kicks in. Limp mode seems to somehow be vacuum related. When I drove the vehicle yesterday and stopped at a light, I would put the truck in neutral and rev it to 1000 rpm......no limp mode all day.

The ABS lights came on and off a few times yesterday.......so I was thinking......if the brake booster was bad causing a huge vacuum leak........this could be causing the limp mode condition.

I found a Chrysler dealer that will deep scan the vehicle for $165........ this will allow a much deeper look at the systems I have not replaced yet.

The new crank sensor seems to have helped some.

HK

 

These truck REALLY don't like the rare-earth spark plugs. Put some standard coppers in there.

 

Plenum gasket can cause BOTH issues.

Not copper!
And just to clarify, "limp mode" is where the PCM sets a default setting so the engine will run due to no reading at all or way out of spec. This doesn't work for vital sensors.