2004 1500 5.7l recurring problem, low idle misfires, no MF under load.

Bills86e · Jan 3, 2024

rpm at idle goes 200. MPG OH counter 7.8 MPG. I had had similar problem so replaced engine. Now have 16k and still cannot figure same code p0300 misfire cylinder 7.
,,
New injectors, spark resister plugs, wires, & coils. All sensors new, checked all last week. last week, & new oil/filter. Pulled driver side valve cover and all in spec.

Can PCM be culprit?

jws123 · Jan 3, 2024

Did you check compression on all cylinders? Its almost never a PCM issue also did you check for vacuum leaks?

Bills86e · Jan 3, 2024

soon as the rain stops. Going to throw another CPS, gets here Friday. How do I check intake manifold? While running I did spray (lightly) but no change in engine rpm.

Bills86e · Jan 6, 2024

OK, I have the fix, I,ll explain. The new CPS resulted in No Change. P0300 is the result of mil light. Low oil pressure makes hemi tick more prominent.
Since the rpm is controlled by the PCM, it is BAD, and I have ordered a Plug & Play PCM from FlagshipOne $228 shipped.
When RPM goes low, there is no way to get it back to 750 RPM.
When the 5.7l goes lower than 650, oil pressures are low to almost non-existant, ticking begins.

This should also return my MPG to normal. I,ll report back.

Queation: Are 4wd shocks compatable with R2wd trucks?

Bills86e · Apr 23, 2024

Will not idle 750, at 200, lifters clattering, op goes to zero oil pressure.
good compression, new HV melling op, freshed oil & filter, air filter, new pcm,
new exhaust manifolds & cats pipes, new battery, throttle body, op sensor,
coils, injectors. This is whacking my brain, I need advice.

Ken226 · Apr 23, 2024

Have you checked the cam/lifters/valve springs.

For us 4th Gen guys, the p03xx cylinder misfire codes usually result in a cam swap or valve spring replacement. Especially on engines that have spent a lot of time idling.

It may not be a cam/valve spring issue at all, but since your scratching your head and out of ideas, it's something else you can check.

I think there was just a thread about this a few days ago in the 4th Gen forum. Similar code, broken valve spring.

Dodge 1500 4X4 · Apr 24, 2024

Ken226 said:
I think there was just a thread about this a few days ago in the 4th Gen forum. Similar code, broken valve spring.

Yes he had a misfire, pulled valve cover and broken valve spring.

Bills86e · Monday at 8:35 AM

After removing the oil pressure switch, discovered oil inside the connector, indicating the switch was blown threw and pressure escaping.
problem solved! Bought a new switch, a TEE with extra port, and a manual gauge to mount on passenger side railing. 65lbs now. Replaced the EGR & PCV,
engine now running smoothly, re-learning the throttle idle now.

Bills86e · Tuesday at 12:38 PM

PLEASE READ: https://charm.li/Dodge or Ram Truck...g System/Alternator/Diagrams/Connector Views/

I am Upgradeing all the goodies, touch screen, oil filtration, lighting, exhausts, to 300 amp Alternator & grounds. My new Alt plug harness needed new orientation.
If you buy a bigger Alternator make sure the field wires are correct, or you will short out the PCM. Got my help from charm.li then click enter.

Yours Truly, Bills86e

2004 1500 5.7l recurring problem, low idle misfires, no MF under load.

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