Missfire Help???
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Missfire Help???
Ok i've been getting a intermitent missfire on my truck for soem time now. It ran great all winter but now its getting hotter it intermitently misses
Last summer I replaced all the coils. And the coil inquestion now was replaced since last summer with Motor Craft Coil.
I have red the check Engine Codes a d here is the freeze Fram data
DTC :P0351
Fuel System I : Closed Loop
Calculated Load: 71.37%
Engine Coolent temp: 199.4 F
Short Term Fuel Trim Bank 1 : 3.91%
Long Term Fuel Trim Bank 1: 0.78%
Short term Fuel Trim Bank 2: 6.25%
Long Term Fuel Trim Bank 2: 0.78%
Engine RPM :1613.25
Vehicle Speed Sensor: 4.35 MPH
Any Idea what might be my problem? Since The Short Tem Fuel trim from bank 1 and Bank two are vastly different could that mean my fuel injector is not working correctly?
Can anyone give me some suggestions please.
Last summer I replaced all the coils. And the coil inquestion now was replaced since last summer with Motor Craft Coil.
I have red the check Engine Codes a d here is the freeze Fram data
DTC :P0351
Fuel System I : Closed Loop
Calculated Load: 71.37%
Engine Coolent temp: 199.4 F
Short Term Fuel Trim Bank 1 : 3.91%
Long Term Fuel Trim Bank 1: 0.78%
Short term Fuel Trim Bank 2: 6.25%
Long Term Fuel Trim Bank 2: 0.78%
Engine RPM :1613.25
Vehicle Speed Sensor: 4.35 MPH
Any Idea what might be my problem? Since The Short Tem Fuel trim from bank 1 and Bank two are vastly different could that mean my fuel injector is not working correctly?
Can anyone give me some suggestions please.
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Joined: Jan 2004
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From: St Louis
You have an electrical problem with the primary side of the #1 coil. It might be an intermittent connector (clip missing?), a wire harness problem, or a PCM problem.
Inspect the connector carefully first.
Inspect the connector carefully first.
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Well the connector was replaced last summer when all this started. The one noticible thing is it happens when the outside temp is 85 degrees or above. I was going to replace the wireing harness but Ford no longer makes the Harness for this year model of truck and I can't seem to find one anywhere.
I've been told by Ford Tech he doesn't think it is the PCM. Cause if it was it wouldn't be intermittent.
I've been told by Ford Tech he doesn't think it is the PCM. Cause if it was it wouldn't be intermittent.
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If when the COP connector was replaced if it was spliced in backwards could that cause a intermitent missfire?
Only thing that has been consistant with the missfire is it only happens when its above 85 degrees outside temp.
Only thing that has been consistant with the missfire is it only happens when its above 85 degrees outside temp.
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That is true. But I have put 3 or 4 new coils on this one cylender last summer with in about 3 months. I first used aftermarket coils and kept replacing cause I was told that was what was wrong. I finally spent the money on a Motor Craft coil last summer. And it still missfired. Guess my next step is to buy one directly from ford and see if it corrects it.
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Today I used a test light to test the COP Connector before it began to missfire. When I did the light would strobe off and on. After it started to missfire today I checked the connector with test light and now the light would just be solid. It wasn't strobing like before.
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Hotshot
Joined: Jan 2004
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From: St Louis
That means it isn't receiving its "grounding" pulses from the PCM which means there is either an intermittent open circuit in the wiring harness or the PCM is bad.
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Since you saw a solid ground on that coil lead from the PCM, you need to chase back the harness to the PCM connector to be sure there is not a rub-through to ground.
At the PCM Pin input for that cylinder, there is a solidstate switch in the PCM that supplies ground to the coil when it's time in the fire order to do so.
Only thing left to do when the trouble is in is to meter that pin for a ground to know it's the PCM Switch.
Normally it should measure about 10,000 ohms referenced to ground not much more or not much less. This resistance is built into the design so testing can confirm it.
Unless you go this far to prove out the trouble you will only be guessing when replacing the PCM for it's total cost and possibly not solve the missfire.
At a dealer shop, they should have what's known as a breakout box to connect between the harness and the PCM to make this test and know for sure if the PCM switch is faulty.
Good luck..
At the PCM Pin input for that cylinder, there is a solidstate switch in the PCM that supplies ground to the coil when it's time in the fire order to do so.
Only thing left to do when the trouble is in is to meter that pin for a ground to know it's the PCM Switch.
Normally it should measure about 10,000 ohms referenced to ground not much more or not much less. This resistance is built into the design so testing can confirm it.
Unless you go this far to prove out the trouble you will only be guessing when replacing the PCM for it's total cost and possibly not solve the missfire.
At a dealer shop, they should have what's known as a breakout box to connect between the harness and the PCM to make this test and know for sure if the PCM switch is faulty.
Good luck..
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