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Random Misfire on 3 cylinders

slimfitz

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Joined
October 7, 2010
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City, State
NJ
Year, Model & Trim Level
06 Limited
Hello all I am pulling my hair out trying to solve a misfire on my wifes explorer. Its a 2006 Limited 4.6 V8. I am getting code p0303 for a cyl 3 misfire. So I swapped coil packs 2&3 cleared the codes. Well the cyl 3 misfire again. I figured it has 130000 miles the plugs are probably bad. So at 13 bucks a piece I bought a set of plugs for it. Still I am getting cyl 3 misfire. So now I swapped injectors 1&3 and cleared codes. I still end up with this cylinder 3 misfire. I am going to borrow a noid light and check the harness now. Has anyone else ran into this issue? Thanks for any help Mike

Edit: Also maybe Im numbering the engine cylinders wrong. Is it the same as all my 302 and 351s? 1234 on pass and 5678 on driver side?
 



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You are correct, # 3 is passenger side bank, third from the headlight. I had similar thing on #8, I found out I had water dripping theer from the windshield. Check for any corrosion inside the well, check the wires going to the coil. Can you test if you have the spark ?
 






Yes I will test for spark tonight when I get home. I have been reading up on it. Seems that a O2 sensor could cause this. But wouldnt that affect the whole bank? Also a plugged cat? wouldnt that affect all cylinders?
 






Got home today verified spark, checked injector harness, and coil harness. Cleared codes. Took it for a short drive and romped on it. Now i have cylinders 1,3,&4 all with random misfires. No other codes. Now this has me thinking that my passenger o2 is bad. But i have no code for an o2. Which o2 adjusts the fuel? Front or back?
 






Got home today verified spark, checked injector harness, and coil harness. Cleared codes. Took it for a short drive and romped on it. Now i have cylinders 1,3,&4 all with random misfires. No other codes. Now this has me thinking that my passenger o2 is bad. But i have no code for an o2. Which o2 adjusts the fuel? Front or back?

Very strange.. Do you happen to have access to a scan tool to see the output of the o2 sensor ? The fronts control the mixture - The rear is only there to gauge the efficiency of the catalytic converter.
 






Yes i have an old school snap on brick scanner. I gave up tonight when i couldnt feel my hands anymore because of the cold here. I will go out in the morning and mess with it some more
 






I went back out there tonight and plugged the scanner in. I could not figure out how to read the o2 readings on this scanner. I thought that it could but I guess not. I am thinking about swapping both of the front o2's and see if it moves to the other side. I see that they are going to be a pita to get to. So this will def wait till tomorrow. Steve hope you guys are warm Im right over in Browns Mills near Ft Dix
 






Well I went out today and pulled the passenger o2 sensor. Could not get the driver side out so I just went and bought a new o2 for the passenger side. Still have the same codes. Just to be sure I swapped injectors again, and now swapped coil packs from the other side of the motor. This is driving me crazy. I want to hook up my fuel pressure gauge but it looks as if Ford for some unknown reason did not put a schrader valve on the fuel rails. How the hell does someone check fuel pressure?
 






Well I went out today and pulled the passenger o2 sensor. Could not get the driver side out so I just went and bought a new o2 for the passenger side. Still have the same codes. Just to be sure I swapped injectors again, and now swapped coil packs from the other side of the motor. This is driving me crazy. I want to hook up my fuel pressure gauge but it looks as if Ford for some unknown reason did not put a schrader valve on the fuel rails. How the hell does someone check fuel pressure?

Definitely been pretty cold lately :) So sounds like o2 wasn't the culprit. I noticed the lack of a schrader valve as well - I think the only way to read the pressure now is with a scanner that can read the correct PID. Honestly the next thing I looked at would be compression on those cylinders since you've just about eliminated everything else. Does the truck seem to have a lack of power ?
 






Definitely been pretty cold lately :) So sounds like o2 wasn't the culprit. I noticed the lack of a schrader valve as well - I think the only way to read the pressure now is with a scanner that can read the correct PID. Honestly the next thing I looked at would be compression on those cylinders since you've just about eliminated everything else. Does the truck seem to have a lack of power ?

Yes the explorer is a dog. Has absolutly no balls. Will only do about 40 MPH and it shutters as it misfires. I wanted to do a compression check but because the triton motors are the only motors to use a 16mm spark plug that adapter is not included in very many kits. My compression gauge had all of them except 16mm. No stores had an adapter local. I had to order it yesterday and it should be here some time this week. It is really driving me nuts trying to figure this out. I put my coolant pressure tester on it today. Lost about 4 PSI over an hr. I figured it may have pushed coolant into a cylinder so I pulled the plugs and turned it over. No coolant in cylinders.
 






Well its confirmed. Cylinder 3 has bad rings and the head gasket between 3&4 is popped. This sucks. I cant believe this motor at 130k is this bad. I change the oil every time the light comes on withen a few days. I just cant fathom it being this bad. Ive had cars where I never changed oil and never had any issues!
 






Well its confirmed. Cylinder 3 has bad rings and the head gasket between 3&4 is popped. This sucks. I cant believe this motor at 130k is this bad. I change the oil every time the light comes on withen a few days. I just cant fathom it being this bad. Ive had cars where I never changed oil and never had any issues!

Well that's horrible news ! At least we know what it is now but it sounds like the worst case scenario. This really makes me worry about mine - I'm only at 83k and also religiously change the oil but I wonder about the design now. My last two explorers with the 4.0 OHV I drove to 225k and 242k and they were still running strong when I sold them.
 






Slimfitz -

that's a bad news, sorry to hear that.

Normally those tritons run way past 200k miles without major issues. Mine is also 06 v8, and I got 150k miles, and it's still strong like new. Have you had it since new ? My guess it was overheated at some point. That weakens all the components, and then it's a matter of time till they fail.

Are you planning to fix it ?
 






Well i dont want to scare you with yours. Mine was probably put together on a Friday right before quittin time. Im still not sure if im going to rebuild this motor or if im just going to drop a junkyard motor in. I was so pissed last night i forgot to put some oil in the cylinders and see if it was the rings on cyl 3. Today im going to go home put a couple tablespoons in in and rerun the compression check. This weekend i will pull the motor and open it up. We bought it with 40000 miles on it.
 












I think you are the first one here that the 4.6 has a major failure. I know mine can go in 500 or 50,000 miles. I'll see what I would do since the overall condition of the truck is still very good.

I was looking at this the other day:

http://www.ebay.com/itm/NEW-REMAN-F...Parts_Accessories&hash=item43b26dea2b&vxp=mtr

I called my engine builder today. He can rebuild this on for that price but hes backed up 2 months. He gave the number of a junkyard that he says is very honest. I called them today and they said lately the 4.6 3 valve motors are dropping like flies. He said i was the second one this week looking for one. He has a 7000 mile 4.6 for 1600. I may go pick it up this weekend before i start.
 






4.6 with 7,000 miles for $ 1,600 is a steal. Just make sure it's compartible with your truck. They stopped making the explorers with 4.6 in 2010 as I am sure you know, and even then I see that 2006-2008 somehow differs from 2009-2010. Probably the one with 7k miles is from Mustang, which should be ok except for the accessories and air intake which you'll swap from yours. Good luck, and keep us posted. I may need your rebuilder one day :) I am probably not that far from you.
 






4.6 with 7,000 miles for $ 1,600 is a steal. Just make sure it's compartible with your truck. They stopped making the explorers with 4.6 in 2010 as I am sure you know, and even then I see that 2006-2008 somehow differs from 2009-2010. Probably the one with 7k miles is from Mustang, which should be ok except for the accessories and air intake which you'll swap from yours. Good luck, and keep us posted. I may need your rebuilder one day :) I am probably not that far from you.

The heads are not different between mustang and explorer? Or cams? I knew there was something about 08-09 being different but was not sure. As far as my engine builder his name is Jerry at Medford Speed. Pretty close to 70 & 206 He does great work. I just had him over the summer put my 408 for my Mustang together. I have never heard anything bad about Jerry. Jerry says he has done a couple of the 4.6 but alot more of the 5.4's
 






If he's so backed up with work, he's got to be good.

So he said about 2 grand to rebuild the motor ?

Thanks
 



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I just asked him for a ballpark figure. He said 2500 would prob do it
 






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