2002 Lincoln LS V6 Gen 1 Electrical? Issue

[shuffman37]

Long story:
2002 LS V6
175,000 miles

Car started stuttering (every mile or so a little jerk, like the engine killing the spark to all cylinders for 1/4 second) after a long trip, about 3 hrs and then died. Car cranked over, good fuel pressure at rail, no start. Waited 15 min, started up drove away. Died 1/2 hr later, waited, restarted, had car towed home 2 hrs.

Brought car home, ran fine, pulled crank sensor and it was cracked in half along the side, got new sensor and installed, checked all wiring to pcm and others around engine bay.

Car runs and drives fine 99.99% of the time, then randomly it will turn "off" for 1/4 of a second while driving causing a weird jerk, then be fine for a random amount of time. Temperature does not matter or time, interior or exterior.

Car has:
-new fuses
-grounds cleaned to pcm and battery
-new fuel pump
-new fuel filter
-new crank sensor
-new TPS
-new COPs
-new spark plugs

I have a scan tool and data readout, while driving when the car hiccups, I get a little blip/drop or drop in the rpm chart. MAF, TPS, IAT, etc are all steady and working normally. Same for voltage, O2 sensors, etc.

Fuel pressure is great, regulator works fine when I blip the throttle at idle with my guage hooked up. Car has good vac, runs great except for the random stutter/hickup.

I have tried my back up key thinking PATS was momentarily killing it, no change. Pulled out the PCM, took it apart and inspected the solder joints and wiring pins, all good! Unplugged the cam sensor and made it run only on crank sensor, same random stutter while driving. Crank sensor wiring is all good and intact, shielded like it should. Seems to be working 100% based off of my live data chart and the quick reaction when the engine switches off during the little stutter event.

I'm really stumped. Car won't throw a code, and I can't see anything wrong with the live data while driving around. Just a little rpm spike/drop when the car blips!

Any ideas?

 

[joegr]

What brand of COPs?
Where the spark plug gaps checked
What "regulator works fine?" (There is actually no fuel pressure "regulator", so it can't be that. Fuel pressure is controlled electronically by the REM commanded by the PCM.)
PATS won't stop a running engine.

 

[milehighmikey]

To me, it seems to indicate a possible random PCM drop-out, and you may be able to find one pretty readily to test with.

I agree that a COP could cause this, and could be very difficult in proving, outside of a completely new set being installed.

Sounds like you have done very good homework thus far, which is refreshing to see.

And as Joe says, PATS only seems to disable the starting circuit.

 

[shuffman37]

To me, it seems to indicate a possible random PCM drop-out, and you may be able to find one pretty readily to test with.

I agree that a COP could cause this, and could be very difficult in proving, outside of a completely new set being installed.

Sounds like you have done very good homework thus far, which is refreshing to see.

And as Joe says, PATS only seems to disable the starting circuit.

Thats what I'm thinking at this point. I've been driving around the past week while viewing live data and can't find anything wrong. When the car acts up, the fuel pressure will drop 5-10 psi during the seizure, had a fuel pressure gauge zip tied to the hood! But, that would correspond with the PCM/REM shutting down for a second and killing the pump. Tried different fuel pump, new relay, swapping relays, etc, no change. I check the data line junction block under the dash where all the modules link together, all the wiring was good and didn't act up when I wiggled them around. Checked wiring going to the REM, all good, no change when wiggling around either. I've got a service manual so I can verify every wiring item in the whole car.

At this point I'm stumped, and without a code it doesn't make sense to swap around any of the computers when I'd be shooting in the dark!

Time to build a diesel powered car with mechanical injection and no computers! 6BT here I come!

 

[tireman]

Just a thought, the AIC valve on the throttle body. It will shut down the V6 in a hurry when it starts to fail. Take it off and clean it well with some carb cleaner, or go to autozone and get their lifetime gauranteed unit. Then when it fails again, you just turn the damn thing back in for a new one. on my 4th in my 2001 V6

 

[shuffman37]

Finally figured it out. Around the same time as the crankshaft sensor quitting I did a partial transmission fluid change. This time I followed the factory instructions of having the car level and running it through the gears, then park and pulling the center plug with it running. In doing so, the transmission ended up slightly over filled. For the past 5-6 years I ran the car with the fluid checked cold non running without any issues. Then I found the thread about warm fluid checking procedure and decided to do it the "right" way.

I remembered the change in procedure. So I drained about a quart of fluid out and the car has been stutter free for the past 3 days, with about 600 miles of new driving. I'm assuming the fluid was getting some air introduced into it and causing the trans to intermittently let go of a gear or let the converter unlock momentarily. The fuel pressure/rpm spikes would match as the car referencing the MAP for fuel pressure calculations.

Still time for a purely mechanical car. The parents 2003 Grand Marquis fell victim to a COP failure! Gotta love salty/wet Michigan roads!