misfire Detected 98 ford Exp

[Billy88]

I had code PO304, which is Cyl #4 misfire, since the plugs were not replace since I had it, I replace them & sure enought #4 cyl plug was all wet, so I figure that was my problem, The car ran great for about a mile or so, then the check engine light came on again & the car was running really ruff.. Got home & now I have codes PO304, PO305, PO306. can you tell me what might be going on?? The engine is a 4.6
Thanks Bill

[blueburbboober]

yes, i second this problem. im working on my pastors 98 and have a misfire on 4 and 8. i thought it might have been the coil, but after replacing it the check engine light came back on in a day. Im gonna try to pull the plug on the #8 cylinder and see what it looks like.

I should point out that i have done the key on engine off and key on engine on tests and NEITHER show ANYTHING wrong. His truck has some random problems with electrical (prolly the rain thing) so im wondering if its related to the computers under the dash. Has anyone had these same problems, and then replaced the computer and they went away????

(btw, its a 98 expy, 4.6 engine, about 125k miles)

[way2old]

Pull the coils on the affected cylinders and look closely at the plug boots. Look for any burn marks that may indicte the spark is arcing through the side of the boot to the head. Squeeze the borrom of the boots and look for cracks. If there are any cracks, replace the boots. While the boots are off, check the springs for corrosion. #4 cylinder is bad for misfiring because of the heater hose leaking antifreeze on the coil causing the plug to short out.

[blueburbboober]

way2old,

thanks for the reply, but the 98's dont use COP. There are 2 coils bolted to the FRONT of the block that serve up the 8 cylinders. It just happens that #4 and #8 are on the same coil, and i replaced the coil. still no go.

as an update: i have pulled the plugs, they look fine. Did tests on the plug wire and they check out as well. I inspected the boots and they also look just fine.

so what is left???? im gonna go chat with the ford dealer and see what they have to say about all this. none of my friends have any more suggestions of what to look at.

thanks for any help,
Rob

[way2old]

Sorry about confusion. We have 98 Expeditions and they have COP. Guess it is a manufacturer date thing. If the wires have never been changed, I would move wires around and see if miss moves. If miss moves, replace the wires.

[Peter99]

Originally Posted by way2old

Sorry about confusion. We have 98 Expeditions and they have COP. Guess it is a manufacturer date thing. If the wires have never been changed, I would move wires around and see if miss moves. If miss moves, replace the wires.

Also you can run the engine in a very dark room and look for spark arching

[Billy88]

Originally Posted by Billy88

I had code PO304, which is Cyl #4 misfire, since the plugs were not replace since I had it, I replace them & sure enought #4 cyl plug was all wet, so I figure that was my problem, The car ran great for about a mile or so, then the check engine light came on again & the car was running really ruff.. Got home & now I have codes PO304, PO305, PO306. can you tell me what might be going on?? The engine is a 4.6
Thanks Bill

OK I got my problem slove, I miss your advice, but I was glad to see I was at lease on the right track.. Thanks for helping.. My problem did turn out to be the plug wires. The engine is so hard to work on, I had a hard tme trying to get the plug wires off, I see they make a tool, but what good does it do when you still can't get to 3-4 of them?? Also it seem to be dry around cyl 4, but when rev. the engine I saw it drip from the heater hose..I hope this helps other people out.. Bill

[way2old]

Glad you got it going. Thanks for the fix post.

[blueburbboober]

Hey guys, thanks for all your help! I too found the problem.

When i posted earlier and siad i checked the plugS, i should have said plug (no S) I only checked the number 8 plug. I talked to MANY people at CALPOLY (the university i go to currently) and someone explained to me the theory behind the ignition system in that truck. According to him, he said that the spark actually travels from the coil, through plug #4, through the BLOCK, then UP through plug #8, then back to the coil. (this is for NON-COP setups) I never checked plug #4.

So guess what i found when i pulled plug number 4? Lots of antifreeze! The heater hose above that plug is leaking. I tried to get it to stop but no luck. I need to replace the hose. Anyone know how they come off? (obviously the one end is a simple hose clamp, but the other one is so far under the firewall that i cant see it)

As for now, i dried everything up and check engine light is off, no misfires. I did get the leak to slow, but its not fixed the right way yet. Thanks again for all your help!

[way2old]

There is no easy way. You need to crawl up in the middle of it until you can see the clamp by the firewall. Sorry.