#4 plug keep fouling, ideas?

compleckz · Jan 24, 2008

4.0 ohv 110k miles

a month ago i was havling a #4 cyl misfire, and random cyl misfire cel codes.. it ended up being the #4 plug was part of the problem, it still sparked, but it must have been weak or something. so i replaced the plug, and it ran good for awhile.

yesterday i had the same poor running misfire condition, and the CEL came on saying #4 cyl misfire.. while trying to figure out the problem last time, i swapped the #4 injector with #6, i also replaced the upper intake gasket, and the o ring in the egr tube. but the intake manifold was dirty scummy nasty, especially around the egr tube.

my only thought is that the egr is bad or something and contaminating the #4 cylinder since its the closest one to the tube. i really dont know what the deal is. idea?

thanks

MAKG · Jan 24, 2008

Are those crusty white deposits?

As in, burning coolant? Are you consuming coolant?

The EGR will not introduce slime into the intake. But the PCV valve might. Oil slime doesn't explain the crusty white deposits.

And that doesn't look anything like a month old spark plug.

And you might want to do something about that valve cover leak. You don't want your vehicle tracked by smell, do you?

compleckz · Jan 24, 2008

MAKG said:
Are those crusty white deposits?

As in, burning coolant? Are you consuming coolant?

The EGR will not introduce slime into the intake. But the PCV valve might. Oil slime doesn't explain the crusty white deposits.

And that doesn't look anything like a month old spark plug.

And you might want to do something about that valve cover leak. You don't want your vehicle tracked by smell, do you?

i am consuming a slight amount of coolant, but i had a small leak at the heater control valve, and i replaced it multiple times--but the new valves developed leaks within a few weeks. i posted about it, and people basically just said the valves suck. i ended up putting some pipe in so it constantly feeds the heater core, but i just noticed today i have a slight leak from one of those connections..

the spark plug was a spare old plug from a tune up last year, i threw in to test last time i had the problem, and it ran great-- so i didn't replace it.

so you're thinking i have a head gasket leak into cyl #4 causing the plug to foul out?

and you say replace the valve cover gasket because you saw all the junk on the spark plug threads?

MAKG · Jan 24, 2008

IF those white crusties weren't there when you put the plug in, you either have a head gasket (or head!) leak, or that new lower intake gasket is leaking. I believe there is a coolant passage next to #4. You can tell the difference with a leakdown test -- pressurize #4 to 100 PSI at TDC/compression with the rad cap off. Bubbles in the rad neck point to the head or head gasket. A blown lower intake gasket will pass a leakdown test because the intake valve is closed.

How does the oil cap look?

Yes, oil all over the spark plug threads is a strong indicator of a nasty and fresh valve cover leak.

compleckz · Jan 24, 2008

MAKG said:
IF those white crusties weren't there when you put the plug in, you either have a head gasket (or head!) leak, or that new lower intake gasket is leaking. I believe there is a coolant passage next to #4. You can tell the difference with a leakdown test -- pressurize #4 to 100 PSI at TDC/compression with the rad cap off. Bubbles in the rad neck point to the head or head gasket. A blown lower intake gasket will pass a leakdown test because the intake valve is closed.

How does the oil cap look?

Yes, oil all over the spark plug threads is a strong indicator of a nasty and fresh valve cover leak.

im pretty sure thats mostly wd40 overspray on the plug, i was thinking of removing the egr, so i sprayed the bolts and stuff.. i probably hit the plug wire and it traveled down.. i do have an oil leak on the front of the engine, so maybe its the vc and it leaked back.

btw i replaced the upper intake gasket, not the lower.. the lower was done 30k miles ago by the dealer before i bought it.

oil cap was a little gooey.. the dipstick looks good. coolant loss is very slow. i also only drive the truck a few times a week now.

the truck dosent seem as fast as it should be for having 4.56 gears.. the jump from 3.27s to 4.56 wasn't as great as i though it'd be.. so maybe a head gasket is going.. the truck seems to over cool sometimes too, if i'd just coasting down a big hill on the highway or something, the temp gets down to like 150-160.. but going up a big hill it can get up to about 210

cwgreen · Jan 24, 2008

I had the same problem. My heater control valve leaked, and after the third replacement, I finally got one that didn't leak. Unfortunately when the leak started, I had no idea the coolant had drained, and the engine overheated. Afterwards, I noticed the front left plug kept fouling, just like yours is. Both heads were cracked, which allowed coolant to leak in and foul the plugs. I've replace the heads and I'm just about finished getting everything back together. Good luck!

compleckz · Jan 24, 2008

well the truck has never overheated, and the coolant reservoir has never ever been empty.. but the situations sound pretty similar otherwise.

time for a leak down test.. i might just make something i can screw into the plug hole and pressurize it with the compressor.. schrader valve style.. leak down testers are kinda expensive, and no one local had even heard of them :temper:

i hate when i look like an idiot in the store because THEY don't know what it is, like im making it up.

MAKG · Jan 24, 2008

No need to make anything. Spark plug hole adapters for air compressors cost like $5. People sometimes use these to replace valve seals with the heads installed.

You only need a leakdown tester to test piston rings. ANY leakdown into the water jacket (or past valves) is bad.

compleckz · Jan 24, 2008

So what would you say about my oil cap?

Mutant Pony · Jan 24, 2008

I would say that you have a boat anchor under your hood. You have the normal 4.0 failure. I could tell you what is wrong but, the last time it started a huge discusion that got pretty ugly. It will run for quite a while that way but, you need to look for a replacement.

MAKG · Jan 25, 2008

I wouldn't quite jump at the boat anchor answer, but I don't like the looks of that oil cap.

There are other leak sites besides the head or head gasket that can get coolant in the oil. Particularly the lower intake gasket, as that can also get coolant in #4. The front cover can also leak coolant into the crankcase.

I'd try the leakdown test.

racinranger · Jan 25, 2008

My 4.0 has a cracked head over number 3cyl.......it will missfire for about 30 seconds at startup then clear up. i use about a pint of coolant a week. After i replace the plug it wont miss for like 2 weeks. then it will go right back to the missing at startup then running good. After about 2 months it will misfire bad all the time, i replace the plug and repeat the process. Its been this way for about a year and a half or 15k miles. so they will live like this just keep changing your oil.

Timbit · Jan 26, 2008

Mutant Pony said:
I would say that you have a boat anchor under your hood. You have the normal 4.0 failure. I could tell you what is wrong but, the last time it started a huge discusion that got pretty ugly. It will run for quite a while that way but, you need to look for a replacement.

I am curious about this quote.....mutantpony..PM me if you want, I am curious to hear what you have to say..mine is acting up and I have major issues I think....

#4 plug keep fouling, ideas?

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