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Constant Misfire 2002 Ford Escape
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drjones5
Novice
Sep 6, 2013, 5:45 PM
Post #1 of 13
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Constant Misfire 2002 Ford Escape
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Hello All,
I have a 2002 3.0L V6 Ford Escape. The SUV began misfiring shortly after purchase and I have been fighting it ever since. After a bit of research when the misfire began I replaced the ignition coils and the spark plugs. I also replaced the upper manifold gaskets since I had to take the manifold off to get to the back three spark plugs.
So, now I'm at a loss. When I first replaced the plugs/coils the car stopped misfiring only to begin again shortly thereafter. Does anyone have any thoughts on what I can try next? I have a suspicion the problem may be in the wiring that sends the signal to the ignition coil to fire the plug. Does anyone know a good way to check this wiring? Would anyone know where I can fine a replacement for this harness? Thank you in advance for any advice.
Best Regards,
DJ
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Discretesignals
Ultimate Carjunky
/ Moderator
Sep 7, 2013, 7:56 AM
Post #2 of 13
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Re: Constant Misfire 2002 Ford Escape
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You need to figure out which cylinder(s) is misfiring.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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drjones5
Novice
Sep 7, 2013, 5:19 PM
Post #3 of 13
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Re: Constant Misfire 2002 Ford Escape
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My engine has the following setup, cylinders 1,2,3 face the front of the car.
456
123
The car fires in this order: 1,4; 2,5; 3,6.
Cylinders 1,2 & 5 have all misfired at some point; 2 & 5 are currently misfiring. I've tried switching the ignition coils/plugs around in the past to try to make sure none of them have failed with little success. That's the main reason I'm leaning toward a wiring issue.
Does anyone know a good way to check the wiring? Would anyone know where I can find a replacement for this harness? Any other thoughts on possible causes? Thanks.
Best Regards,
DJ
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Discretesignals
Ultimate Carjunky
/ Moderator
Sep 7, 2013, 5:32 PM
Post #4 of 13
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Re: Constant Misfire 2002 Ford Escape
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You can inspect the wiring, but to see if the PCM is triggering the coils you need a labscope to watch the primary coil ground circuit or you need to current ramp the coils.
If you find there is no triggering going on for those coils, you need to figure out if it is wiring, input problem, or PCM driver issue.
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
(This post was edited by Discretesignals on Sep 7, 2013, 5:33 PM)
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drjones5
Novice
Sep 7, 2013, 8:15 PM
Post #6 of 13
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Re: Constant Misfire 2002 Ford Escape
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A labscope is a little out of my price range. Is there anything else I can use to test the wiring?
I don't mind trying to replace the PCM. However, I've already replaced the ignition coils. The coils/plugs are about 8 weeks old now, should I still replace them? Thanks for all your advice.
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Hammer Time
Ultimate Carjunky
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Sep 7, 2013, 8:20 PM
Post #7 of 13
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Re: Constant Misfire 2002 Ford Escape
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No, you don't have to change them twice.
You could get a noid light and backprobe the pins at the PCM to determine if you have pulse coming out but you first have to figure out which cylinders are causing the problem.
You can't change the PCM yourself because it has to be programmed in the car immediately or it won't start. They can install the basic program out of the car but the keys have to be registered in the car before it will run.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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drjones5
Novice
Sep 7, 2013, 8:40 PM
Post #8 of 13
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Re: Constant Misfire 2002 Ford Escape
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Thank you for the info. I'll check for a pulse first. Is the pcm programming something my local mechanic can do, or should I take it to a Ford dealer? Thanks again.
DJ
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Hammer Time
Ultimate Carjunky
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Sep 7, 2013, 8:45 PM
Post #9 of 13
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Re: Constant Misfire 2002 Ford Escape
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There are very few independent shops capable of programming. They would have to be auto electric specialty shops. You would likely be using the dealer.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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drjones5
Novice
Sep 14, 2013, 1:40 PM
Post #10 of 13
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Re: Constant Misfire 2002 Ford Escape
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Update:
I picked up a HEI spark plug tester, pulled the fuel pump ISO and tested the ignition coils. Only coil four has been missing recently.
Sure enough, no spark out of # 4's coil pack. I swapped them around to be sure that it was the coil and not the harness.
So, I switched out the faulty coil pack for a new one and put new spark plugs in the front. I'm sure that this wont be the last of this misfire since I've had problems with the coils under the upper manifold plenum.
Guess, I'll wait and see. This seems to rule out a faulty PCM, unless it's only acting up occasionally. Doesn't seem like a burned-out driver. The harness also seems to be in good shape.
I guess time will tell, misfire is gone for now.
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drjones5
Novice
Sep 14, 2013, 3:18 PM
Post #12 of 13
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Re: Constant Misfire 2002 Ford Escape
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Well the plugs looked rich, and it cost me all of five dollars to put new plugs in while I was already under the hood.
I expect this won't be the end of the misfire, but for now the car is running fine.
I did notice that the engine valve cover is leaking oil around the seams today. Most of it looks old, however I may look at putting in a new gasket if it continues to leak. Also, fyi, the plugs didn't look fouled with oil and the coil boots were clean.
Thanks for your help,
DJ
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Hammer Time
Ultimate Carjunky
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Sep 14, 2013, 3:32 PM
Post #13 of 13
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Re: Constant Misfire 2002 Ford Escape
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The coil boots would have nothing to do with plug fouling. They are on the outside of the combustion chamber.
What was stupid is replacing only 3 plugs. You should always do 6 at a time. You don't leave 3 old ones in simply because it was too much work to change them.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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