Misfire diagnosis needed....99 Crown vic


rusty ol ranger

2.9 Mafia-Don

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1987
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2.9 V6
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Manual
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Thought i had it licked...im starting another thread because the other one derailed...and i got better info now.

Symptoms...

Cuts out around 30-35 under heavy throttle...sometimes will totally lose power....normally wouldnt stall but it did today. Shut it off, it fires right back up, and generally wont do it again untill it sits for a while. Im also getting the red battery light...totally randomly. Sometimes its on for a second...sometimes for a minute...volt gauge never moves and electrical power seems to stay. It is also now...sometimes...missing after you come to a stop. Sometimes after 10min of idleing, sometimes right away, lights also weirdly pulse during this...and its a crap shoot if the battery light lights up during....again...shutting it off and restarting makes it all go away. About 50% of the time it will act like it wants to stall going into gear...it dont...but it bogs out and then kinda chugs back to life. I also for the first time tonight felt what im pretty sure was torque converter shutter.

Codes im getting are for "primary control circuit open/short"...for cylinders 4/5/6/8. One cylinder (4) on pass side bank, 3 on the drivers. For some reason cylinder 7 seems immune...despite its bank mates going crazy.

Also...here are some missfire counters that i have no idea about...

20260322_220445.jpg

20260322_220404.jpg


According to the google one of those usually indicates a random/mutiple missfire the computer cannot pinpoint...

So why am i getting specfic codes?
Why does shutting off the key and then right away firing it back up clear everything up?

Why does it only happen early on in drive cycle and under hard acceleration or at idle?

This almost has to be the PCM at this point dont it? Along with the shudder i couldnt recreate and a trans that acts perfectly normal otherwise?

Can some of the heavy hitters chime in here? Im literally pulling my hair out.

Should add...All 8 plugs/coils are new (motorcraft), cam sensor/pigtail are new, intake manifold is new, MAF is new, alternator is new, starter is new, battery is basically new, cats are new, fuel pump is new..ive checked every ground on the thing and they look new (its only been in the salty north a couple years)
 
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sure as fawk sounds like it to me.
 
the converter clutch bumping could be the stall. there is a myriad of reasons that can happen and not report.


this should have a mechanical throttle body.

so the heavy load should be recordable. what is that you posted pictures of? can it record the drive cycle and see what it is doing like hp tuners?
 
the converter clutch bumping could be the stall. there is a myriad of reasons that can happen and not report.


this should have a mechanical throttle body.

so the heavy load should be recordable. what is that you posted pictures of? can it record the drive cycle and see what it is doing like hp tuners?

Mode 6 is a Forscan thing
 
there is a power issue clearly.

whether its corrosion in the pdb or just a bad main connection down fuse of the battery is hard to say.

i actually suspect several power issues.

didnt you already swap ecms? the damage you have found already i would look careful at the fuse boxes.

generally there would be other anomoly happening with radio and windows lights ect if its a flood rig. you dont seem to have too many issues that way. does it have a police package wiring setup in the pdb? maybe a main power connector is loose from equipment removal and arcing out...
 
flood car?
No not a flood car.

the converter clutch bumping could be the stall. there is a myriad of reasons that can happen and not report.


this should have a mechanical throttle body.

so the heavy load should be recordable. what is that you posted pictures of? can it record the drive cycle and see what it is doing like hp tuners?
I dont think so. Its a maddox md14 scanner from harbor freight. The reason i was wondering about the shudder is it would go away as soon as you hit the OD off button. Thats why i figured it was trans and not motor.
there is a power issue clearly.

whether its corrosion in the pdb or just a bad main connection down fuse of the battery is hard to say.

i actually suspect several power issues.

didnt you already swap ecms? the damage you have found already i would look careful at the fuse boxes.

generally there would be other anomoly happening with radio and windows lights ect if its a flood rig. you dont seem to have too many issues that way. does it have a police package wiring setup in the pdb? maybe a main power connector is loose from equipment removal and arcing out...
Not a police car. I have not changed PCM. I do have some weird lighting issues but other electrical seems fine, but like i said i cant find any rust or a waterline inside or anything along those lines. Carfax doesnt say anything about a flood. It was a salvage title...but it was in an accident when it was like one year old.

The fuse boxes also look clean and very normal. As do the two big main connections under the brake booster. Wiring harnesses also look unmolested.

One thing i forgot to add in original post...when i checked voltage with DVOM it it was showng 14-14.2, but once every 30secs to a minute...itll drop off to high single digits for a split second then come back. No idea on that one
 
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Ok....

Its gotta be a power issue. I just drove it to work. About 15mi. Totally normal until i got about a mile away. Started slowing down for a stop sign...i had blower on full blast and high beams. Volt light started blinking, this time the volt gauge dropped, blower slowed, lights dimmed...car was still running fine.

Took off from stop (normally), battery light still flashing but everything else returned to normal. Engine lost power, flatlined, and was missing when i pulled over. Shut it off, started right back up, and everything was fine.
 

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