cylinder 4 misfire

[LouisianaEx]

Hey everyone I have a problem with my 02 explorer 4.0 w out flex fuel. The sohc. I've replaced the spark plugs, Coil pack, and wires. What should my next step be? The problem just seems to be getting worse. I also put fuel injector cleaner in and premium fuel with no luck.

 

[Honestmase]

Check for a vacuum leak. I found a huge hole on a 3/8 ID hose on top and in front of the engine. It was a 90 degree bend, and the hole was under the hose so you have to feel for it. It will crumble in your hand. Only 20k miles on it!

 

[2000StreetRod]

check compression

A vacuum leak usually results in random misfires in multiple cylinders. If you have a repeatable #4 misfire I suggest checking the compression.

 

[LouisianaEx]

It was a problem in my head. Just took it apart and the valve spring was broken into 3 pieces. I had a warped exhaust valve as well. Getting that reworked this weekend. How do I go about putting the head back on? Does the cam sprocket have to be in any specific position, or just make sure the cam shaft "nub" is in the right position? When taking it off I didn't check to see if the pistons were in any specific position either. Will I have to hand turn the motor over to put the piston in a certain position?

 

[2000StreetRod]

retime camshaft

Did you release the jackshaft front sprocket retaining bolt? If so, then both camshafts will have to be retimed. If you only removed the left camshaft sprocket retaining bolt then only the left camshaft will have to be timed. Trying to use the camshaft position nub to time the camshaft will not be accurate. You will have to use the timing slot on the firewall end of the camshaft.

If you don't have the OTC 6488 timing tool kit you can get the timing within a few degrees of accurate by using the hydraulic tensioner to make the chain taught. With it installed and piston 1 at TDC on its compression stroke the timing slot should be below the axis of the camshaft and parallel to the head surface that mates with the valve cover. I think shown below is the right camshaft timing slot with the piston at TDC (using the damper timing mark) and on the compression stroke (no valves depressed).

Before installing the head you should rotate the crankshaft until piston 1 is in the correct position. There should be no interference because the right camshaft is still correctly timed and the left head is off. When you get the left head back will it be completely assembled with the camshaft installed? If so, then rotate the left camshaft until it is in the correct position before installing the head. That will avoid interference problems on the left side. The timing nub should be in the position shown below.

If you PM me your email address I'll send you the SOHC V6 assembly instructions.

 

[LouisianaEx]

Yea when I get it back it will be completely reassembled. Thanks for your help. We only removed the left head so only that sprocket and camshaft will be wrong. I've checked the piston and 1 is up and so is 5.

 

[2000StreetRod]

timing slot?

Make sure the timing slot on the right camshaft is in the correct position when piston 1 is at TDC. It could be on the compression or the exhaust stroke. If its on the exhaust stroke the camshafts will be 180 degrees out of phase if you install the left head with the camshaft position sensor nub above the camshaft axis. The OTC 6488 tool kit will only fit with the slot below the axis. If you don't use the kit then you can time the camshafts with both slots below the axis or both slots above the axis. The only function of the camshaft position sensor nub is to "tell" the PCM if cylinder 1 is on the exhaust stroke or the compression stroke. The engine will start (but run poorly) with the camshafts 180 degrees out of phase. The injectors will pulse at the wrong time so the fuel charge will be "stale" when the intake valve opens. There is also the possibility of piston to valve interference so get it right before starting the engine.

 

[LouisianaEx]

We didn't take the right head off..do we have to do that?

 

[2000StreetRod]

just the valve cover

You only have to remove the valve cover to check the camshaft timing.

 

[LouisianaEx]

What do I look for on my right head? It doesn't have the nub? Just took the valve cover off.

 

[2000StreetRod]

timing slot

See the second photo in post 5. The timing slot should be below the axis on the camshaft and parallel to the head surface that mates with the valve cover when piston 1 is at TDC on the compression stroke.

 

[LouisianaEx]

Ok thanks! That slot is parallel and we have the piston 1 up judging by the spark plug hole. Now we just have to work on the left head. It looks like the mechanic put the camshaft back on with the nub up in the correct position.

 

[LouisianaEx]

Well got it put back together and it makes the loudest rattle noise so looks like it may be time for a new car. I may just sell this one for parts.

 

[LouisianaEx]

Decided to give it one last look over and this time it is the primary chain tensioner broke and the balance shaft guide broken. Just removing the balance shaft chain and going to replace the primary chain and tensioners tomorrow. I'm ready to get this thing complete! This is the last thing I'm changing on it! Moving on after this!

 

[2000StreetRod]

balance shaft chain guide

The balance shaft chain guide can be replaced without removing the block cradle. It is only necessary to remove the front timing cover which you'll be doing for the primary tensioner replacement. The block cradle only has to be removed to replace the balance shaft chain tensioner.