Ford explorer misfire issue


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Old 06-02-15, 04:57 AM
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Ford explorer misfire issue

HI all,

Have an issue with my 2003 ford explorer 4.0 engine and 75,000 miles. The vehicle runs great 90% of the time. It seems to act up only when it rains out and is damp. The other day ( Sunday) it poured out for the entire day, late in the day I drove it to the store about 2 miles away, no issues. On the way home after about a mile it started to misfire. it wants to stall at idle ( but doesn't) and there is no power. You can step on the gas and you hardly accelerate, then all of a sudden it will kick in and surge ahead. The check engine light came on and flashed ( flashing means misfire in fords). Got it home ( smelled bad at the rear where the exhaust pipe is) and it sat for about an hour and then drove it again for about 4 miles with no issues ( engine felt fine) other than the check engine light stayed on steady. The next day drove it again and was fine and after about 3 miles, started to do the same thing but the CEL didn't flash this time just stayed on. Kept driving it and after about 2 miles, it went away and it drove fine the rest of the 8 mile trip. Drove it later in the day back home 8 miles with no issues. I stopped at Autozone and they pulled the codes for me. There were two in there, PO152 ( circuit condition Heated O2 sensor bank 2 sensor 1) and PO175 ( Fuel bank 2 trim condition, ECM has detected a rich or lean air/fuel mixture on engine bank 2). I am hoping with these two codes someone can give me an idea what this could be or two try and troubleshoot. It is frustrating that it happens so infrequently a few times a month when it rains. I took it to a repair shop but at the time the CEL was not on and they found no issues. They hosed the engine down with water ( I have done the same thing at home) but it didn't do it and with no codes they weren't sure. I replaced the spark plugs and wires a year ago and they supposedly checked some of that out when it was in there. Any help would be greatly appreciated. I Will try to do some additional troubleshooting on my own prior to taking it back to the shop. Today I started it up and the CEL was off and it drove fine the 8 miles to work. Hasn't rained since Sunday. Thx
 
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Old 06-02-15, 10:18 AM
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Perhaps you need to take a look under the vehicle. Maybe there is a loose electrical connector that is getting moisture inside it and shorting out when the roads are wet. Could be a bad ground that is just barely making electrical contact and the humidity/rain makes it worse to a point where it is noticeable. Check your battery connections, ground connections, and even the horns, because they are right in front of the grill and get wet.
 
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Old 06-02-15, 10:23 AM
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took a garden hose and completely soaked the underside for about 5 minutes spraying everywhere. Didn't cause the issue.
 
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Old 06-02-15, 10:29 AM
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First thing I would do is check your coil. An intermittant misfire in wet weather is usually a good indicator. Hopefully when you replaced the plugs and wires you used some dielectric grease as you reassembled them.

I find it odd that you didn't have a misfire code if you say the engine is misfiring.

Part 1 -How to Test the Coil Pack (Ford 3.0L, 3.8L, 4.0L, 4.2L)
 
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Old 06-02-15, 10:35 AM
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XSleeper got to it first, but for what it's worth--a few possibilities:

https://answers.yahoo.com/question/i...3104011AAZEZKj
 
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Old 06-02-15, 10:35 AM
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I can check into the coil. The Ford manual says if the CEL is flashing then it is misfiring. Not sure why it didn't set a code for misfire but the light was flashing numerous times until it finally stayed lit all the time. Also, I didn't use deelectric grease when i installed new plugs. I should probably put some on there.
 
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Old 06-02-15, 12:18 PM
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Go back to the basics for a minute. When it misfires, determine which cylinder it is buy using a test light. Short out each cylinder one at a time. Whichever cylinder doesn't make a change, that's the culprit. Change the spark plug wire in that cylinder & see what happens.
 
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Old 06-03-15, 10:20 PM
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You can try spraying down the coil and plug wires on a regular basis with WD-40; especially at times of the year when there's a lot of rain or it becomes very damp and foggy. It works.
 
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Old 06-04-15, 04:55 AM
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I don't understand the obsession with WD40. There are so many better products. PB Blaster is one although I wouldn't use any of them on spark plug wires. If the dampness is affecting them, I would install a new set.
 
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Old 06-06-15, 09:52 AM
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The reason I suggest WD-40 is because I've been a mechanic for 35 years and have found it to work.
PB Blaster is fine as a penetrant for rusted fasteners but I'd never consider it for use on ignition components.

WD-40 is a water displacement product that also repels moisture. Sometimes a no-start can be caused by moisture accumulation inside of a distributor cap on cars fitted with distributors when the environmental conditions are right. This means the dew point, etc.
Spraying the cap down with WD can prevent that.

If a spark is jumping from a plug wire or plug boot the first thing to consider is the age and miles on the spark plugs. Misfiring plugs due to miles, excessive gap, etc will cause the spark to jump to the cylinder head because that spark is going to go somewhere to ground no matter what.

A new set of wires can help but even those can misfire depending upon the moisture in the air or even accumulated water if the plugs are iffy.
 
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Old 06-06-15, 06:57 PM
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Before PB Blaster, I used CRC in place of WD40. I don't see that particular CDC product any more. That's why I didn't mention it. I worked steadily as a mechanic for some years starting in 1969 & even then WD40 was not my first choice. The funny thing about it is that if I need something in a pinch, there always seems to be a can of WD40 around. So I use it anyway. It must be my destiny.
 
 

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