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Help, Phantom Misfire


Explorermandan

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2002 explorer limited v8
Hi,
I have a misfire on my 02 limited explorer. It runs ok when cold, but once it warms up, it has a rough idle, and misfires under light load in lower rpms. At WOT, the engine surges and the HP curve is not smooth at all.

I've ran fuel injector cleaner twice, changed the plugs, and changed the COP's. As a result of my efforts, the trouble codes indicate that after each attempt to fix it, a different cylinder goes bad. Right now it says that cyl 1,2, and 8 are misfiring.

Any Ideas? It seems odd that the problem would move, and correct me if I'm wrong, but those cylinders are on different banks, so its probably not an O2 sensor? Is the car sensitive to the type of COP's? I replaced all with Granetelli's from summit racing.

The truck is all stock except for a CAI from my '00 mustang. It also has the Mustang Mass air sensor, but its run fine for over a year.

Help please!
 


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rocco123

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Have you looked at that 90deg rubber elbow that leads into the idle air controller? Also look for other vacuum leaks.
 




pet575

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Possible short in the wiring feeding the COPs? Might be a reach but sounds like you might be at that point anyway.
 




Adam Black

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Have you check the spark plug wires? If those have any excessive resistance/opens or abrasions, it can cause misfires.
 




rocco123

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He mentioned cyl 8. So its a v8. No plug wires just coil on plug COP
 




Explorermandan

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Thanks for the replies. I've glanced around for vacuum leaks, but I'll look closer tomorrow. I thought about the cop wires being loose, but if it's moving around, I kinda ruled that out.. it's worth a look though! crossing my fingers..
 




zpn_by

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What brand replacement COP part did you use? I've heard varying reports about the reliability of many off-brands. Honestly it sounds like you're working on my truck as I had the exact same misfire pattern you did. #1, cleared, drove OK. #2, cleared, drove OK. #8 Cleared, drove ok. Funny thing was it actually ran better with the CEL on solid than when it was off...

When you changed your coils, did you reuse the boots, or did you at least run some dielectric grease inside the opening (not so as to get on to the plug contact itself though... I finally got my code to repeat on a saturday when I had my sockets and scanner handy, and chased it down to a bad #1 (consistently). Went to the wreckers, and got myself three newer motorcraft coils (funny thing, all the engines had replacement COP's on them - wonder why...) I replaced the faulty one and now keep my scanner and the two spare COPs in the trunk....

+1 on checking the wiring. Also double-check the connections for your cam sensors - if you are in a moist/wintry area the connections may be corroded. Possible that although they aren't throwing codes they may think they are registering a misfire. Did your CEL blink or just come on solid?
 




rocco123

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I used accel. Amazon for 200. They come withboots and yes dilecteic grease. Tore an old boot tip due to being stuck.
 




Explorermandan

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sorry for the delay, I used granetteli cops. I checked for vacuum leaks and couldn't find anything. all the wiring looks and feels intact. This all started happening shortly after having the fuel filter changed along with the oil. maybe some debris went up the line and its messing with the injectors? the cel came on and didn't blink. I'll look into the cam sensor wiring. I've also read reports that if the wrong engine oil is used, it can also cause misfires. that makes no sense to me, but that's a cheap fix if that's the issue.
 




Explorermandan

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also, I used plenty of dielectric grease. I was under the impression that too much was ok, and it was supposed to be in contact with the boot wire as well as the plug post.
 




JCUZ

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I have a misfire on mine - #5 cylinder (closest one to thermostat housing). My CEL only ever blinks - what does that mean as opposed to a solid CEL light? I have 3 different sets of COPS (so 24 all up), and when I get the misfire, I simply change the hot COP from #5 for a cold one, and off we go again, until it does it again 5 miles down the road (literally). Very frustrating.

What brand replacement COP part did you use? I've heard varying reports about the reliability of many off-brands. Honestly it sounds like you're working on my truck as I had the exact same misfire pattern you did. #1, cleared, drove OK. #2, cleared, drove OK. #8 Cleared, drove ok. Funny thing was it actually ran better with the CEL on solid than when it was off...

When you changed your coils, did you reuse the boots, or did you at least run some dielectric grease inside the opening (not so as to get on to the plug contact itself though... I finally got my code to repeat on a saturday when I had my sockets and scanner handy, and chased it down to a bad #1 (consistently). Went to the wreckers, and got myself three newer motorcraft coils (funny thing, all the engines had replacement COP's on them - wonder why...) I replaced the faulty one and now keep my scanner and the two spare COPs in the trunk....

+1 on checking the wiring. Also double-check the connections for your cam sensors - if you are in a moist/wintry area the connections may be corroded. Possible that although they aren't throwing codes they may think they are registering a misfire. Did your CEL blink or just come on solid?
 




zpn_by

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I have a misfire on mine - #5 cylinder (closest one to thermostat housing). My CEL only ever blinks - what does that mean as opposed to a solid CEL light? I have 3 different sets of COPS (so 24 all up), and when I get the misfire, I simply change the hot COP from #5 for a cold one, and off we go again, until it does it again 5 miles down the road (literally). Very frustrating.
First things first, if it blinks, pull over & power off ASAP. It means there is a misfire which may be dumping raw gas (or LPG) into your exhaust and possibly damaging your catalytic converter.

Big question for you - does it only happen when running LPG or gasoline? If when on gasoline, you may have a bad injector, if when on LPG, that's beyond my experience. Is your LPG system running multiple injectors? It could also be wiring too, or even the boot or plug itself. Have you changed the spark plugs recently, and did you use anything other than Ford Motorcraft? These engines (so I'm told) are very finnicky with plugs... Are you actually getting the P0305 code? It could be a loose connection on that COP, or a brittle/broken wire too, if it is that code.

I know it's lots to check or confirm, but these were steps I went through with troubleshooting my truck. I ended up getting three Motorcraft COP's from the local wrecking yard. I changed the bad one, and keep the two extras as spares. At least there is lots of storage space in the truck, so I have my code scanner, basic hand tools, and a full socket set with me at all times. Too bad that I have to, but I can't swing the $$ for a whole new set of COP's...
 




rocco123

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Check the torque of the plug to be sure its not ready to spit one out.
 




zpn_by

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be careful checking the torque - the problem of stripped threads can come from over torquing the plugs. If it's spit one out, you'd know for sure, plus it would come with the boot when you remove the coil. That was a big problem on many trucks, but I'd wonder if the LPG is causing a problem for JCUZ (although in my city, the 4.6L Crown Vic cop cars are all LPG and don't seem any worse for it)

JCUZ - check your alternator's condition and output - if there isn't enough juice, then the COP at the end of the circuit might be suffering. In this case #1 or #5. I've heard from users on other forums that an underperforming alternator could cause spark problems too.
 




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