2004 Ranger Cylinder 4 misfire

[Willard]

So I recently bought a 2004 Ranger Edge with the 3.0L in it, and for the most part it runs beautifully.

However, I keep getting p0304 (cylinder 4 misfire) and a p0316 (misfire detected on startup) codes along with a slightly rough idle. I was only getting the codes on hot startups, and even then they didn't come around much. The plugs I just replaced with Autolite platinums, the wires test fine, they are fairly new Beldens. I cleaned the MAF with no change. While testing different things, I noticed that when sitting hot and idling for a few minutes, the misfire condition becomes noticeably worse, up to the point where it is a constant misfire and the CEL starts blinking. Rev the motor up for a minute, CEL goes out and it starts running smoother again.

It is definitely not a complete miss, but it also isn't firing a strong as the other cylinders. I took it out for a short drive and afterwards the idle was smooth and there was no misfire, until it idled for a bit. This only happens when the truck is warm, it doesn't do it when cold. I checked the upper intake gaskets by spraying carb cleaner around the area but the idle didn't jump. There doesn't seem to be any other vacuum leaks. This truck only has 84,000 on it, and given that for the most part it runs fine I seriously doubt there is anything internal going on, especially because this truck has definitely been taken care of in it's life. Pretty much everything is in perfect shape.

Anyways, this is bugging the crap out of me so any suggestions would be appreciated.

[Tbars4]

..Just my personal assessment on the 3.0's and this is if they do not even have the other problems that the 3.0 w/ flex fuel has..

..I have helped a number of people out here chasing that same problem on the 3.0 Rangers of different years..

...Head problems are common on the 3.0 and until they are swapped with new and not rebuilt you shall be chasing these symptoms as they keep changing..

...I've had Dealerships tell me this is a known issue and they have even swapped the heads under a resale warranty for the customer/ one of my friends truck...On the other hand, I have had guys from the dealership swear they never heard of head problems with the 3.0..

..The best way to chase this is by doing compression test...

..This of course is only if you have already ruled out bad wires/plugs, bad ground on coil pack, etc..

....I would also check on your header panel for the info to what plugs you are required to run..IIRC, most newer 3.0's run only the Iridiums and the single platinum will not work right and may cause misfires..

..If you could take a picture of that may help others to for what to look for..

[Willard]

Yea I know about the head issues, it would seem to me on such a low mileage motor it shouldn't be a problem. I do need to do a compression test, just haven't been able to do it yet.

It doesn't say anything anywhere about running Iridium plugs, so I will assume for now the platinums are fine. The coil pack hasn't been tested, I need to do that too, but I believe it is fine.

The truck runs great most of the time, its just the hot idling its having problems at. Even still it isn't that noticeable, I've driven vehicles that idled worse when they were running correctly.

[Tbars4]

..Curious but what does it say on your header panel sticker? It should have a plug number and gap on the bottom of the sticker.

..I was wrong on another 3.0's plug and am wondering if the iridium is a Cali only thing..

[Willard]

It doesn't say anything under the hood about the plugs other than the gap. However, I looked in the owners manual to see what plugs it had listed, and it just said to take it to the dealership. That kind of tips me off about the plugs being strange. I found a service manual so I will see if its in there

Edit: I should mention the sticker on the truck says it conforms to us and cali emissions. Perhaps it is a cali truck

[Willard]

So I looked around, the plug that is listed for my truck on the motorcraft website is a nickel plug. I looked and I can get Iridiums for my truck, but I can get all types of plugs. So who knows. It is strange the part number for the plugs is so hard to find.

[Tbars4]

..I do know for sure that the 2006 3.0 cali Ranger requires Iridium plugs and it is on the sticker..

..The one Ranger 3.0 I was wrong about before had no plug info like yours and I had them change from the platinum to the dbl platinum and they said that helped them a lot...

..I am not saying it is your fix but if I had the funds and even if I did the compression test, (until I swapped the heads), I would try the DP's..

[Willard]

I'm tempted just to throw some iridiums in there anyways since I believe they are supposed to be the best plugs.

I drove it again just now and on the warm start there was initially no light but after a minute it came on. Ran the codes and I had one for random multiple misfires in addition to the others this time. Seeing as how it seems to be getting worse as the plugs break in I feel like they may be causing the problem

[Tbars4]

What were the plugs you took out?

..It is not unheard of to get a faulty new wire or plug when they are brand new..

..You can easily move the #4 wire and plug over to another cylinder to see if the misfire moves with them. I wouldn't rule out firing order either.

[Willard]

The plugs that came out were new Bosch Platinums that came in the truck, that's the main reason I replaced them in the first place.

The wires tested out fine, but I do need to swap them and see if that's the problem. I doubt firing order is the issue, as it runs smooth as silk at anything above idle.

Thanks for the suggestions so far Tbars

[Tbars4]

The plugs that came out were new Bosch Platinums that came in the truck, that's the main reason I replaced them in the first place.

....Did you swap the Bosch out due to the known problems in our vehicles when using them or were you already getting misfire codes?

[Willard]

Both, actually.

[Willard]

Okay, so compression checks out even through all cylinders, so that should help rule out a head issue. I swapped wires with no change, tested as well and they all have very low resistance.

I looked up the spark plugs on the motorcraft website by using the VIN number and it came up with platinums and nickle plugs. However, I'm still tempted to try some Iridiums just to see what happens. I'm also starting to run out of ideas on this one. Could a camshaft position sensor be part of this at all?

[Tbars4]

..Did you swap the plug and what were your compression readings?

..Usually a CPS just goes..Unless you know of it or other parts recently being swapped in just before purchase till now..

[Willard]

I don't remember the exact compression readings, they were all within 10 psi of each other though. I didn't swap the plugs, I should try that and see what happens. I do know it through the same codes with the bosch plugs, which leads me to believe they aren't the problem.

[Tbars4]

p0304

..This definitely tells you you have a problem with the wire, plug, or that cylinder.If it was a coil pack they usually fault on 2 cylinders at a time..

..I would also make sure your spout connector is in place, timing belt (chain?) and timing are good..

..I'm running out of ideas and would still bet on the heads but if I were you and while searching the forum, I would keep an eye on this new thread as some other ideas may come up on it..
http://www.explorerforum.com/forums/...d.php?t=351690

[Willard]

One more thing for right now until I go tinker some more... OE plugs for this truck are Motorcraft part# 432. They are not the normal platinums, they are special ones. Maybe that is the problem.

[Tbars4]

..Hopefully someone with information on that specific plug will join in here..

..But yes, there are several factors taken into account for spark plugs which most people do not even think about..

..Even though a parts house spits out a certain number for your vehicle only means it is what they are selling as a common plug for your vehicle..

..I believe this to be the true oem p/n for your truck..

P/N SP-432 / AGSF32FM

[Willard]

So I went ahead and got a set of the SP432s and put them in. For starters, somehow I had the gap about .10 too big on the other ones, so that wasn't helping for sure.

However, the problem is still there. I drove it for awhile and it definitely felt better though. I haven't gotten a CEL yet, and I let it idle for awhile in the driveway, where I observed something else. It only has the miss when in park with the A/C off. I cranked the A/C and idled in park, no miss. I put it in gear and let it idle, no miss. So under any load the problem really doesn't exist.

The plugs that came out all looked perfect, including the one out of cylinder #4. I'm thinking it wouldn't hurt to maybe run a seafoam treatment or at least put something in the gas to make sure I just don't have a dirty injector for some reason. I also wouldn't be against removing them and cleaning them outside of the truck.

Is there anything else I can do to check the head out without actually removing it? If that is the problem I will probably just run it as is until it gets bad, and I could also try a little stop leak to see if that fixes things up for now.

[Runnin'OnEmpty]

Originally Posted by Willard

......... It only has the miss when in park with the A/C off. I cranked the A/C and idled in park, no miss. I put it in gear and let it idle, no miss. So under any load the problem really doesn't exist........

This is very strange....

I've seen problems like this that turned out to be
something very simple, but will drive you crazy very
quickly.

Maybe clean the coil pack top. Spray or pour alcohol
on the coil top and wipe it down good. If a terminal has
started arcing it will make a carbon track and cause a
misfire. Clean the terminal boots. I'd also be tempted
to change the plug wire, since a break in the insulation
could cause the miss and the wire resistance could
still check good.

You can open the hood on a dark night and see if there's
any arcings....

The coil pack is still a suspect.