Shall I say frequent misfire 4th cylinder

[Doug.Spencer]

2000 XLS 4.0 OHV

So this is really starting to annoy me. My explorer seems to throw the 0304 code or whatever the misfire in cylinder 4 code is. And so I replace my plugs and wires. But within months, it will all of a sudden start running rough and boom check engine light comes on (not blinking) and the truck starts running like crap. I honestly have had the plugs and wires replaced and EGR cleaned three times in the last year and a half. But it always seems to eventually misfire again. And when it does, it is horrible to drive, rpm's fluctuating like crazy and what not.

I've been searching through a bunch of threads and I've noticed some talking about the upper gasket, I believe, beginning to leak and coolant gets in there and fries that plug.

That made me start to wonder, I've noticed that MY X doesn't seem to hold onto anti-freeze, and I seem to always be a little low in the reservoir or out. So the other day and I filled it back up with anti-freeze. It drove fine to work, but on the way home it immediately ran rough and the check engine light came on.

It also seems to happen if it is cold and I don't let the car heat up enough before driving that that starts the downward spiral towards the misfire.

Do you guys think that it would be my upper gasket is leaking or something else? I don't think it is the plugs or wires, seeing that they have been replaced enough, and it only happens to the 4th cylinder.

 

[SoNic67]

Pull the plug out (and post a picture). Antifreeze on it might be visible as ash deposits or even wet (when it does not fire anymore).

 

[corkey]

i might say with the symptons described that i would pull that plug and look and see if that is where the coolant is going,,

if it keeps misfiring it has to be for some reason,,

maybe do a compression check too,

 

[herebyproxy]

my 2 cents

You may have a cracked head as I have. It leaks coolent into a cylinder very slowly and that spark plug may develope a tiny crack in the insulator where the electrode sticks out. I have to add about a cup of coolent every month.

 

[Dono]

my experience was exactlt as tou describeed. slow coolant loss, and having to replace a plug every so often.
Then the issue started on the second bank also.

short story, replaced both heads. No coolant loss now, not going thru spark plugs, and way better mileage and power.

 

[Doug.Spencer]

I'll pull the plug out tomorrow and see what it looks like.

If the head is cracked then I got a few questions.

1) How exactly do I confirm the head is cracked?
a. Compression check
b. Spark plug with ash or wet from coolant.
c. Other test?

2) Cost wise, what is a rough estimate for the new heads, I assume it would be the best idea to do both?

3) What causes a cracked head?
a. Does the coolant leak cause the cracked head, or the cracked head cause the coolant leak?
b. Or does the cracked head have nothing to do with a coolant leak. Ha

4) Last question where is a good place to look for new heads, I would assume that is not something I would want used? And what would be a reasonable price?

 

[Dono]

You need to do a leak down test on the cylinder that keeps loosing the spark plug.

You will see bubbles coming out of the radiator cap with the cap off.

Cost? Might be a throw away unless you are willing to do the work yourself.
I did mine myself -twice. :-(

Heads are $500.00 Gaskets. $200.00. Labour? 10-11hrs for a novice. (Me).

 

[Dono]

Round 2 I took the heads to a machine shop before re-installing them as things didn't work out so well the first time. $350.00
Id say do this to be sure they are ok no matter where you get the heads from so they can be vacuum tested for leakage, and fixed accordinglt.

Your going to be an easy $1000.00 in to the repair.

Do a leakdown test first though to be sure.

And the factory heads are weak. You overheat the motor once, and the factory heads are cracked.

 

[Doug.Spencer]

Update to my issue.

In reply to Dono, My X has never overheated, so I don't know how the head would have cracked.

So today, I was heading over to my parents house to pick up the code scanner, and some tools. My truck ran like crap there, I didn't think I would even make it the 1 mile drive. I plugged the code scanner in and it read a misfire on 4 and 6. I erased the code. Turned the truck on and let in warm up to it's normal temp. It drove back like normal perfectly fine, no studdering, unusual revving, crazy vibrations.

This blows my mind. If I drove it home perfectly fine, could the head still be cracked or could it be just a leak? Cause the cylinder obviously fired normally. Is this a computer problem? Fuel injector?

I find it odd that so many people on the forum with the OHV engine have had trouble specifically with the 4th cylinder. What is going on with it? UGHHH

Should I still do a leak down test to be sure to rule that out? Or something else?

 

[Dono]

If you have a compressor, a leak down tester is pretty cheap and would tell the story for sure.

Or, if it were me, I'd just drive it and see how it goes. Keep an eye on the coolant reservoir and see if it keeps getting lower. If it is, you know the coolant is going somewhere.

I bet I drove my truck for close to a year with a cracked head. When my second head cracked (In the same spot as the first head) I decided it was time to do something.

I'm told the factory castings of the heads are weak in the one spot. Aftermarket castings don't have this issue.

 

[Doug.Spencer]

This may sound stupid and me trying to avoid replacing the heads, or likely a new engine.

But could it be my EGR.

The last time my engine really acted up like this my EGR needed cleaning as well as plugs and wires. Could it be since it is cold that the EGR acts up, but when the engine is warm the issue goes away? Hence replace the EGR?

 

[Dono]

The real clue that makes me think its a cracked head is that your motor is sucking coolant, and you have not reported a sweet smell while driving, or a coolant leak under your truck when parked.

That and all of our experiences here with this motor is that this spells cracked head.

My motor actually ran for years sucking coolant before it became so bad that it started tearing thru plugs(Then I ran it for another 8 months, replacing a plug as required). Sucking a little bit of coolant thru the motor isn't going to hurt a thing. You might just be ok.

 

[Doug.Spencer]

Good Point.

I should add that I've never seen coolant on the ground, but I have noticed that after driving if I lift the hood it's got that distinct odor of coolant, kinda gross. Also when I first start it for a bit it will puff white smoke out the back for awhile.

All in all it sounds like eventually I will have to either tackle the heads or replace the engine seeing how expensive replacing the heads could be.

Just curious on two more things.

1) Could this issue have been amplified by having just used Seafoam for the first time?

2) And if the problem gets unbearable, it would be in the better interest for me to swap the engine. I got a friend that does all the work I can't do on my truck. Is a swap for a 5.0 feasible? I'm sure that would entail much more money and time than a simple swap for a rebuilt OHV. But I've been looking at rebuilt engines online with warranties and 5.0's are much cheaper than an OHV. Could a rebuilt OHV still have the crap heads, and soon break on me?

 

[TheJackal]

I had a similar problem once with the #4. My engine does leak so I immediately thought it was gasket related, but inspection of the plug didn't show anything abnormal. Took it to the dealer and they just replaced the plugs and wires, and all seemed good, even though the plugs were not that old.

Well a month later the issue comes back and figuring it has to be coolant getting into the cylinder I bring it in and expect the worst. Come to find out it was bad wiring to the coil pack. They fixed it and I haven't had a problem since. (Well, the coolant still leaks, but so far no evidence it is leaking into the engine.)

Check for spark at those cylinders; if it is not firing, it is an electrical problem. :exp:

 

[corkey]

my plug problem ended with this,

that was what was in my oil pan, coolant mixed with fairly new coolant,, ugh,,

 

[Dono]

If your smelling coolant under the hood, it could just be upper intake gaskets also.
Maybe both.

Its impossible to know.

Some guys will say its easier to pull the motor to do the heads, but I did mine motor in without any issue.

No solid answers, sorry.

I say do a leak down test, and take it from there.

Listen to the other guys experiences, this is why you could have anything, or a combo going on. I never did ask, what does your oil look like, anyway. If its milk, dont drive it anymore, you will trash all your bearings and then you will be dropping in a rebuild.

 

[moogvo]

To answer your question about the Seafoam, No. Using seafoam will not cause a mechanical problem unless there was something wrong to begin with. At the most, it may uncover a problem, but you would have had the problem soon enough anyway.

Before you start buying parts, however, you DO need to KNOW what is wrong with it. You don't want to replace an engine over a clogged injector...

I had the same problem on my '01 Sport. I bought it from a dealer and 3 days later it started throwing a P0304. I took it to a shop where they thought that the intake gasket might need replaced. They replaced it and no good. It did not fix the problem. A leak down test confirmed a blown head gasket... you can also go to your local auto parts store and get a "Block Tester". This is a device tht you put some special fluid into and then use a vacuum ball to pull air out of your radiator and across the fluid. If the fluid turns yellow, you have exhaust making it's way into the coolant... very bad! If it stays blue, that is good, but not definitive. So. I would start there since most auto parts will let you use the tool for the cost of the fluid.

I found that there was low compression on cylinder 4 and 6 as well. The diagnosis was not good at all. I immediately started researching how I was going to get my 3 day old car back on the road without mortgaging my house to pay for it. The price of repair ranged from 1900.00 to 2400.00 from one shop to the other.

Now, bear in mind that low compression is no guarantee that it is a head GASKET... It COULD be a cracked head or a cracked block. You have to think about this before fixing. This COULD run into a crapload of money really quickly. here's what I did...

I was able to force the dealer where I bought the car to take care of this over a legal technicality, but for the purpose of this discussion, that doesn't matter.

We found a 4.0L SOHC engine out of an '07 Mustang with only 30,000 miles on it. The engine was bought complete for $700.00 and put in. The labor was another $700.00 for a total of $1400.00... LESS than even the LOWEST cost of repairing the engine that was in it. As an added bonus, my engine went from 130,000 miles to 30,000 miles. WELL worth the swap... ESPECIALLY if I were to pay for it.

the 4.0L SOHC long block found in 06-present Mustangs is identical to that of the Explorer. You DO, however, have to strip the 'stang engine down to the block and heads and replace everything with your Explorer externals... not a big deal. There is some talk about a balancing shaft on the engine on the 4x4 models. I blew it off and didn't go through the hassle of making them install one on the Mustang engine. I have noticed no difference whatsoever.

At the end of the day, you COULD spend $350.00 per head for 2 heads for a total of what you COULD buy the whole low mileage engine for. (not to mention the special timing chain tool kit at about another $500.00). Along with that is the peace of mind of the updated timing chain problem. not only that, but you really have NO idea what other damage you might find while you are inside the engine.

even if you have all of the tools and DIY the repair, you will STILL probably spend as much (if not more) than just sticking a 'stanger in it to begin with. I absolutely LOVE mine and am glad I have a low mileage engine in it instead of a repaired engine with 130k on it.

Just my .02.

 

[RomeovilleIL]

So today, I was heading over to my parents house to pick up the code scanner, and some tools. My truck ran like crap there, I didn't think I would even make it the 1 mile drive. I plugged the code scanner in and it read a misfire on 4 and 6. I erased the code. Turned the truck on and let in warm up to it's normal temp. It drove back like normal perfectly fine, no studdering, unusual revving, crazy vibrations.

This blows my mind. If I drove it home perfectly fine, could the head still be cracked or could it be just a leak? Cause the cylinder obviously fired normally. Is this a computer problem? Fuel injector?

Sounds like a typical head gasket leak or cracked head. When the engine is cold, the cylinder doesn't have enough spark to completely ignite the antifreeze seeping into the cylinder. Once the engine gets warm and the antifreeze is heated to 190-ish degrees, the spark plug is able to burn it off with the gas in the cylinder since it is already close to boiling temp.

A compression test will tell you if the cylinder has a leak in it, though not if the leak is from a crack or gasket. The only way to make that determination is to pull the head. Sometimes the cracks are tiny so have them inspected and trued. It happens often enough that people don't see an obvious flaw and just bolt them back on with new gaskets only to see the problem reappear shortly afterwards.

If you ultimately plan to replace the engine but need some time then leakstop products do work well as TEMPORARY fixes to this type of problem. It will make a mess inside the cooling system and leaves crud that will have to be cleaned out if you decide just do the heads. But in the interim, you'll be amazed how much better the truck runs by sealing it up with a bottle of barsleaks in the coolant. Once again -- keep in mind it is NOT a fix, only a bandaid to get you by until you are ready to repair it the right way.

 

[moogvo]

Not to step on any toes here, but here is what "Stop Leak" is good for... These are the head gaskets from my Bronco II after someone used Stop Leak to "fix" a water pump leak. It also resulted in replacing the radiator and sealed up the heater core quite nicely. Oh yeah... and caused the head to crack and the head gasket to blow. Stop leak products don't just seal up leaks. It is like flushing a bag of Quickrete down the toilet to seal a plumbing leak! If you DO choose to band-aid your vehicle with some, just know that it is a ROYAL PAIN to get it out and you WILL have to get every bit of it out of your cooling system once you are fixed. That stuff is T-R-O-U-B-L-E! Just sayin'.

 

[Dono]

Wow, stop leak works just like advertised. Fills any spot where coolant can move thru.
Thanks for the pictures.

Being that you have a OHV, you don't have to worry about any timing chains or anything.
I'd say if you are mechanically inclined at all, this isn't a big deal. If you are going to have to pay someone labour, you have some thinking to do. Its probably not worth it.