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Scott W.
Scott W., Technician
Category: Lincoln
Satisfied Customers: 3288
Experience:  28 yrs. experience as Ford ASE Master Technician. Accolades include being a 2005 Ford PTS Regional Finalist and 2006 ASE Ford National Technician.
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I am working on a 1995 Crown Victoria with a P0302 Misfire

Customer Question

I am working on a 1995 Crown Victoria with a P0302 Misfire code in addition the A/C goes to warm when the code is thrown. I think the A/C is a Blend door because this model has the auto air. It seems odd though whenever it throws a code the A/C drops out,
I am sure this is coincidence, but I thought I would mention it. So far I have change the spark plug (See pic), plug wire, swapped ports on the coil pack and replaced the suspect coil pack. In addition I have done a compression test both dry and wet and it
is almost exact to the other cylinders, I tested the injector with a OHM meter and all is good compared to the others, and I have used a noid light tester it works like the others but once it misfires it goes off, I assume this is by design. I have not been
able to get the car running smooth or keep it from throwing the same cyl. 2 misfire code. Could you please help me discover what I might be overlooking. The spark plug in cylinder 2 was black at the bottom, carbon? No oil etc. The car has only 61,000 original
miles on it and it is a 1995.
Submitted: 1 year ago.
Category: Lincoln
Expert:  Scott W. replied 1 year ago.
Hello my name is Scott
Customer: replied 1 year ago.
Hi Scott! Does everything make sense?
Expert:  Scott W. replied 1 year ago.
I was looking at a wiring diagram, the injector wiring circuits are all separate, I don't believe in 1995 the computer would disable the injector for a misfire. I suspect you have a wiring concern from the PCM to the #2 injector, or a bad PCM. Have you checked the injector wiring form the PCM to the fuel injector, tested with a good load like a headlight bulb?
Customer: replied 1 year ago.
Scott,So just to be clear do the same test as I would with a Noid Light Tester but with a light bulb for a head light? Just to add some more info. If I turn the car off and then back on the Noid Light Comes back on even if the code has not been cleared. I just dont want to have to buy a $300 PCM if it is not truly bad. Do you think that I have properly diagnosed everything else, do you think it is cylinder related? It was properly maintained at a Ford Dealership before it was purchased. Do you have a suggestion of where to by a PCM at the best price/quality?Thanks so much!Keith
Customer: replied 1 year ago.
Could you describe how I should plug in a headlight to the wiring harness? Copper jumpers?
Customer: replied 1 year ago.
Sorry one more thing, would the A/C issue be possibly associated with this?
Expert:  Scott W. replied 1 year ago.
No, the PCM connector and injector connector are to be disconnected, then ground one end of the white wire, then use a headlight bulb and socket to test the wire, 12 volts to the battery one end of the headlight bulb wire, then the other headlight bulb wire to the white wire, since you have grounded one end of the white wire, the head light bulb should light up, if it does the wiring is good to the injector, the other wire should have 12 volts on it while key is on or running, I would check the other wire while running and the misfire occurring, if there is 12 volts or more, that wire is ok and I would suspect the PCM since you have replaced all the ignition components.
Expert:  Scott W. replied 1 year ago.
The ac compressor could be turning off because the idle speed may be just slow enough to shut it off. If the engine rpm drops too much the PCM will disable the ac compressor.
Customer: replied 1 year ago.
Fantastic Scott! So essentially you are wanting me to do a continuity test on the wire itself between the injector end and the PCM end? I will do this test tomorrow or Thursday and get back to you so we can wrap this one up! You have been most helpful.
Expert:  Scott W. replied 1 year ago.
Yes, that is correct. Thank you, ***** ***** with the repairs!
Customer: replied 1 year ago.
Just curious... do you recommend a place to get PCM's for a vehicle this old... I would like to start pricing one out just in case. Thanks again!
Expert:  Scott W. replied 1 year ago.
We use Napa or autozone, they have rebuilders of these and we have good luck since we can't get Ford ones because of discontinued parts.
Expert:  Scott W. replied 1 year ago.
Or you could try for a used one also at a salvage yard.
Customer: replied 1 year ago.
Scott,I was not able to do the test because I do not have the pin out at the PCM side. I understand it is important to put a load on the wire because the Noid light does not pull much. With the testing I did today, I have 20 years of electronic back ground, I am thinking it is not the wiring. Let me know if my logic is sound. Here are some tests I did today:This is a cylinder 2 misfire...Test 1
Plugged the light into cyl 2 injector cable with a cold engine and cleared codes. Running a/c at full.
Light blinked on and off like it should
After 5-7 minutes the light stops blinking.
Code for misfire on cyl 2 present.
Turned car off did not clear codes.
Turned car back on and the the light was back to normal.
I let the car idle for another 5-7 minutes, and once again the light was off and the behavior was repeated.Test 2
Plugged a Noid light into cyl 2 injector cable and cyl 3 injector and cleared codes. Running a/c at full.
Light blinked on and off like it should on both, perfectly synced.
After 5-7 minutes the light stops blinking on cyl 2 injector cable but 3 was still performing properly.
Code for misfire on cyl 2 present.
Turned car off did not clear codes.
Turned car back on and the the light was back to normal for both.
I let the car idle for another 5-7 minutes, and once again the light was off and the behavior was repeated for cyl 2 injector cable.With the idea that the light comes right back on after shutting off the car and then starting it back up, it makes me believe that continuity is ok because if the cable becomes loose, frayed, or even too warm it would not work immediately after turning it off and then back on again. I did find the PCM for this vehicle and it is right at $, programmed for this model, no flash needed.
Expert:  Scott W. replied 1 year ago.
I would call you but my phone died, would you like to talk to another expert, or continue this conversation here in chat?
Customer: replied 1 year ago.
No worries at all, chat is fine! Did you get my last question by chance?
Expert:  Scott W. replied 1 year ago.
I can get you the pinout if you want. Yes noid lights pull virtually no current. Yes I would say based on these test results you have a bad driver inside the PCM for cylinder 2 injector. I would replace the PCM and then retest.
Customer: replied 1 year ago.
Scott,Thanks for being so quick to respond and providing great support. I will keep you posted. Hopefully this can be put to rest!Thanks again!Keith
Customer: replied 1 year ago.
Oh yeah, a pin out would be helpful for reference, but no hurry.
Expert:  Scott W. replied 1 year ago.
Here is a pinout.
Expert:  Scott W. replied 1 year ago.
Here is the wiring for the pins.
Customer: replied 1 year ago.
Scott,Here is where I am now:1) Installed refurbished and pre-programmed PCM.
2) Misfire occurs much more rarely but does occur but along with it sometimes I get P0755 Shift Solenoid B error sometimes in tandem with the generic misfire. I have never had this error before. However the A/C never gives out so that seems to be working great! I can drive/run the car for an hour turn it off and right back on and I get a misfire on the 2nd cyl.
3) My thought is that the injector is dirty or clogged so I used the Lucas Fuel Treatment.
4) I changed the oil and added Lucas Stabilizer.
5) I ended up changing the second Coil and replaced all of the spark plug wires.
6) I used Seafoam.> The car does run a little rough when it is idling.Thanks!Keith
Expert:  Scott W. replied 1 year ago.
Try swapping injectors and see if the misfire follows the injector. It could also be a roller cam follower with a flat spot on it holding the valve slightly open.
Customer: replied 1 year ago.
Scott,Good news! I went ahead and purchased a new injector and replaced it today and the engine is purring and not throwing codes. Now all I have is the new error Shift Solenoid B (My guess is because the old PCM was bad it was not properly sending this code as it should), which I purchased along with a gasket kit, filter and Mercon V. I purchase the Permatex gasket sealer but the gasket is rubber... is it still advised to use it? I really appreciate your help through this!Thanks again!Keith
Expert:  Scott W. replied 1 year ago.
That is great news, you are halfway there. I wouldn't use any sealer, as sometimes the sealer will break loose inside and plug the filter.
Customer: replied 1 year ago.
Scott,Well I dropped the pan replaced the shift solenoid A and B (They come together in this model), inspected the wiring and re-seated the connectors for all solenoids, replaced the filter and cleaned the pan. There was minimal sludge and the fluid didn't look/smell bad. I did reuse the gasket because it is the Ford gasket that was is awesome shape and it fits better then the Wix gasket that came with the filter. I torqued the pan to 16 ft lbs and put Mercon V back in. I then cleared the PCM. I then added additional fluid after a test drive. The gears are still adjusting but I did get the same shift solenoid B P0755 error so far. Is this typical? This error didnt show up until I replaced the PCM. Do you think it could be bad also. I am sorry for all the questions, but this one is driving me nuts! :)Thanks again!Keith
Customer: replied 1 year ago.
Scott,I will let you know if it reappears... I was thinking it might have just appeared if the fluid was too low at that time, because I added some later after it had ran through the system.-Keith
Expert:  Scott W. replied 1 year ago.
Here is a pinpoint test for the code, since the concern happened after the PCM replacement, I tend to believe either there is a bent pin in the electrical connector for the PCM, or the PCM is bad itself. Try reintalling the old PCM and see if the 755 returns.

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