Misfiring under load

[Dave96z34]

Iv been fighting with my car for a week now under load she will bog down and register a misfire and flash the SES light at me. only code present is 300... Problem gets worse as it reaches operating temp

So far iv changed
Fuel Filter
Plugs
All 3 coil packs
Ignition modal
Spark plug wires
Mass air
Fuel Pressure Regulator
Injectors
Injector Harness
PCM
Cam Position sensor

So im out of ideas the only sensors I haven't changed are the front and side crank sensors and the hole harness its self... Help!
Every time I drive it it seems in the logs the bad cylinder changes around.
Scan.zip

[SappySE107]

cylinder 1 compression test, and leak down test. Might be head gasket, valve seats, or valve stem seals.

[Schurkey]

Iv been fighting with my car for a week now under load she will bog down and register a misfire and flash the SES light at me. only code present is 300... Problem gets worse as it reaches operating temp

So far iv changed
Fuel Filter
Plugs
All 3 coil packs
Ignition modal
Spark plug wires
Mass air
Fuel Pressure Regulator
Injectors
Injector Harness
PCM
Cam Position sensor

So im out of ideas the only sensors I haven't changed are the front and side crank sensors and the hole harness its self... Help!
Every time I drive it it seems in the logs the bad cylinder changes around.

I don't see the coolant temp sensor listed. Is the computer getting appropriate info from the CTS? System voltage acceptable? No excess alternator ripple to confuse the computer?

Aftermarket electronics interfering with computer/sensor signals?

If this were in MY driveway, I'd start with compression and leakdown tests just as have been suggested already.

[Dave96z34]

Did a compression test 183 to 195 on all cylinders.
Don't have a leak down tester.
Coolant sensor on scans is normal.
As for alternator ripple unplugged it and went for a ride on just battery no luck.
No after market gear on the car to interfere.
Voltage at ignition is normal but could be a bad relay not pushing the amps?
I know my valve stem seals are shot she burns oil fast.

[SappySE107]

I was checking your voltage too, and I have a similar issue with mine. I get 13.4-13.7 volts according to HPTuners, but with a multimeter, I am at 14 volts to the AC controls. Mine is a swapped harness so I thought maybe it was wiring somewhere but yours reads low too. Maybe its the 97 computer itself.

I don't think that is your issue though.

[Dave96z34]

And fuel pressure seems normal

[vcrvi]

Just had an issue like this with my daughters 3800. Found one of the new plugs I had installed a few months earlier
had cracks in it .

[whiteyz24]

One spark plug wouldn't cause a random misfire, if you have a fuel pressure gauge strap it to the windshield and go for a drive your fuel pressure should go up with rpm. It sounds like a fuel pump problem to me, especially since you replaced half your car already

[SappySE107]

This isn't random, its cylinder 1 almost all the time. Spark plug did this to me too.

[z34phoenix]

I can't open the log on my phone so will need to check it tonight. Seems all the usual suspects have been tackled. Maybe something with the o2? Exhaust leak or intermittent sensor data? Any recent changes to the bin file? What do the intake temp sensor data look like? Could be causing spark retard or advance

[Dave96z34]

So I Made a longer fuel pressure gauge today went for a drive and for no reason after I got to the parts store it cleared and drove normal again. NO new changes! Maybe alternator ripple, bad fuel or bad grounds but im happy shes driving again. But no clue. Registered a few miss fires all review it later and all get a few better logs to post on hear all the misses I saw were low rpm like 750 looks like false stuff from the trans bearings and clutch.

[Dave96z34]

Bad Fuel... not buying HESS any more....