99 Ex throwing 4.0 OHC p306 misfire cyl 3

[ProjectAviator]

My 99 Explorer XL is throwing a P306 misfire cylinder #3. It also does throw a p171 lean condition. It has new wires replaced the plug twice and also a new coil. Runs like crap sputters and bucks. Most of the time. She barely can get it over 45-50 mph. I did use some blue devil head gasket fix. It worked for about 4 days now back to the same.

This is my 4th OHC sec gen. Never had this problem with any others. This is the fist manual 2nd gen. I am wondering what is the next step. I need to check the cooling system and the compression.

thanks

Tim

 

[EB4X]

Others on here say K-Seal is best choice....of course no guarantees.....assuming dreaded cracked head....did you / P.O. overheat it ??

 

[koda2000]

Sorry there are no easy answers to your issue... The one weak point on the OHV 4.0L engine is a tendency for developing cracked heads. Sometimes the K-Seal is enough to plug the tiny crack(s) that can develop between the valve seats.

You've stated you have the OHC 4.0L and on the SOHC engine cracked heads are not usually an issue. As you also have a lean code on bank one, it might also be fuel related, or a vacuum leak. Have you replaced the fuel filter? If the fuel filter is severely clogged it can cause lean codes, but that will usually throw P0171 and P0174 codes (as it will effect both banks). If you have a vacuum leak effecting only one bank it could be time to replace the upper and lower intake manifold gaskets, which is very common on the SOHC. Finally, you might have a clogged fuel injector on cylinder #3.

If it were me, I'd start with the intake manifold gaskets/O-rings. While the engine is apart, you might want to test/replace FI #3 and replace the O-ring seals for all 6 FI's while you're in there. There are YouTube videos on how to clean & test FI's if you want to try that route.

 

[ProjectAviator]

I have gotten the p171. I will look into changing the gaskets and #3 injector.I haven't over heated it. Not sure if the po did as I got it from a lot.

Tim

 

[410Fortune]

you can TEST the injector while it is out
Do not buy cheapo parts store injectors they are junk. You need bosch 4 hole just like stock
MOST stock injectors that are not firing can be brought back with a simple bench cleaning.....

If the head gasket repair improved your situation for 4 days....well you need to do some simple tests to see if its a bad head gasket/head.....
was the plug wet? Is there coolant loss? Why did you add head gasket repair? (You must suspect an issue)

 

[EB4X]

With the XL model it has to be an OHV .....never heard of SOHC in that model....but yeah confusing way to list engine description....

 

[koda2000]

With the XL model it has to be an OHV .....never heard of SOHC in that model....but yeah confusing way to list engine description....

You my be correct. I've never even seem an XL, but I know they were ultra entry level/fleet type vehicles.

OP - What's the 8th character of you VIN? E or X?

 

[ProjectAviator]

It is an OHC vin code X. it is a basic model. 5 speed, no tinted windows, utility white color. When I ran the code through the help program at work. ( I work at a major autoparts retailer) it pointed to a possible head gasket. I checked and I can get OEM motorcraft injectors for it.

Tim

 

[ProjectAviator]

I just went out and did some checks. I am losing coolant. There is no white residue inside the oil cap.Oil level is dead on with no milkyness. I pulled the #3 plug. Driver side closest to the firewall. it was nice and ash gray no dampness at all. Being that I broke the insulator clean off I had to put in another plug I had.

now I am at a loss. on what it could be. With the plug being how it should be. ????? what is the cylinder location, coil order of the 99 OHV.


Tim

 

[EB4X]

Spray some ether / starting fluid around intake edges and see if idle picks up, if it does then you know the intake gasket(s) is one of your problems. Start it up and smell exhaust and see if it smells sweet - coolant smell / and or white steam coming out exhaust. And please don't state 'OHC' anymore....lol....

 

[rasouth]

I had a similar problem with mine... bucking, jerking, misfire, loosing coolant. Problem was a blown head gasket letting coolant into cylinder. The other part of the problem was my wires. I did not have them routed the proper way and one was shorting out, causing a misfire.

 

[ProjectAviator]

Did a coolant pressure test yesterday. it fail pressure dropped. I have discounted the head and gasket. I am now looking at intake gasket.

Tim

 

[410Fortune]

discounted head and gasket?!! what?
sounds like you found a problem

 

[koda2000]

A VIN of X is referred to as an OHV, not a OHC. An OHC (AKA SOHC) is very different than an OHV.

The OHV engine can leak water into the engine's intake through the intake manifold gaskets and due to a cracked head or leaking head gasket. I don't know what you mean by "discounted head and gasket" after finding a cooling system pressure loss. It sounds like you should be looking and intake gaskets, or maybe a cracked head or leaking head gasket.

 

[fast_dave]

@ProjectAviator

Just saying - $0.00 required;

Make a "reference mark" on your coolant overflow tank and carefully follow the coolant level - a horizontally orientated piece of painters tape works great.

Give it at least 3 - 5 days of heat & drive cycles, carefully watching the coolant level, and it should give you an idea what's up.

Sometimes the problem is just small enough, and requires the "right" conditions (high heat or high vacuum or high engine vibrations or all combined) to show it's head, that pressure testing (alone) won't show it...

Hope that helps & report back!

 

[rasouth]

Do as EB4X suggested. Spray some starting fluid around intake while engine is running. If there is a leak your engine will rev up.
Have you done a compression test on the cylinders ? That would tell you right away if it is a head gasket problem or not.

 

[ProjectAviator]

Dave, I had filled the coolant and when doing the pressure test 5 hours later. After driving it 10 miles to work and letting it cool. It was down.

Tim

 

[fast_dave]

Dave, I had filled the coolant and when doing the pressure test 5 hours later. After driving it 10 miles to work and letting it cool. It was down.Tim

@ProjectAviator

Hey Tim - looks like you're looking at the following:

Leaking Lower Intake Gasket OR Leaking Cylinder Head Gasket OR Cracked Cylinder Head OR a Combination of any of the three listed.

Suggest that you visually check the front lower intake gasket (which is easy and obvious) but more importantly the rear lower intake gasket (harder) before digging deeper down the rabbit hole in both Time & $$$$.

Note, even if you do not see any external leaking from the Lower Intake Gasket, there is a condition that the lower intake gasket can suffer which can't be seen without removing the Upper Intake Manifold. In short, the lower intake gasket cracks and literally gets sucked into the air/fuel passages.

BELOW is a link to an external thread that has some good pictures of that cracked/sucked gasket condition - specifically Post 37 of the linked thread

Link: Coolant Loss - 4.0L OHV Lower Intake Gasket - Ford Truck Enthusiasts Forums

Hope that helps - report back.