Sorry but this is a really long initial posting. I have tried alot so I figured I would give as much info as I could.

Here's the problem. I have a misfire on cylinders 1,2,and 7 that I can not figure out.

The story is that I was leaving to go out of town just before Christmas and was going to be pulling a trailer to Kentucky. Before I got 15 miles down the road, my truck started to run really rough. I lost power, had a really bad shutter when the pedal was pressed lighty and was going through gas like it was going out of style. While moving I thought I had developed a really bad drive train problem but when I got to a point to turn around the truck was idleing really rough. I managed to limp back to the house and rented a van so my wife and I could make the trip.

When we got back, I started looking into the issue. I pulled the codes and I was showing misfires on cylinders 1,2,3,5,7, and 10. The first thing I did was use start checking the COP's since they are the most likely fault with misfires. I pulled the number 1 COP and tested it with an ignition tester. I was getting a good spark so I didn't think that was the problem. I decided to start checking the plugs which is when I discovered another issue that may have been contributing to the problem. The numbers 2 and 3 plug had previously rejected their plugs and I had it repaired at a local shop that has done alot of work for me previously. They repaired the plugs with helicoils which prior to this event, I had no idea could be a problem all its own. Anyway, when I pulled the #3 plug, the coil came out with it. Since then, the #2 coil pushed into the cylinder. Fortunately while the engine was off. I have since repaired both of these. For what it's worth, the CalVan insert kit is awesome. It was really easy to use. Fortunately, the hole that you bore for the CalVan repair was large enough that I was able to pull the helicoil back out of the #2 cylinder with a small magnet on an extendable rod.

Back to the plugs, the plugs I pulled out of the #'s 2 and 3 cylinder were completely shot. The electrodes looked like they blew up and the grounds were burnt almost halfway back to the threads. I replaced all of the plugs and none of the other 8 appeared to have any real issues. They were all clean and seemed to be burning fine. I then replaced one of the COP's and moved the others around so that I could figure out whether or not I still had some that are not working correclty. I reset the computer and tested the truck. It still idled/ran extremely rough. After pulling the codes again, I was still getting trouble codes on cylinders 1,2,3, and 7. I did some more research and decided to look at the COP boots. I replaced three of them, the #2 cylinder has a brand new COP. Now I am down to misfires on cylinders 1,2, and 7.

I have read that it could be a vacuum leak, a fuel pressure problem, or a clogged cat. I pulled the cat and got no change. I have checked and can not identify any vacuum issues and I rulled out a fuel pressure issue since it appears to be a cylinder specific issue. I have cleared and pulled the codes atleast six times and the issues always involve the same three cylinders. Interestingly, I can pull the misfire codes off the computer but apparently the problem is not bad enough to cause the computer to turn on the check engine light.

At this point I am totally lost. I can't afford to just throw money at random parts so I fall at the mercy of the experts on this forum. For what its worth, my truck is an '01 Excursion with 250K on it. It has a clean K&N filter and I recently cleanded the throttle body and the MAF. Any input would be greatly appreciated.

 

I have read before that sometimes when the coils go bad you do not necessarily get a CEL. I had a misfire problem a while back sounds simliar to yours (running rough, feels like the truck is shaking, no CEL). I had new plugs in mine as well. I replaced all the boots, NONE of the actual coils, and that fixed my problem.Some of the boots looked good others were rusty and/or cracked. It really sounds to me that you have bad boots or entire coils that are failing. I would try buying a few new coils and see if that helps.

 

Do a compression check.
What you described for the spark plugs does not sound "normal".
If all cylinders are within 10% of each other, you can probably rule out piston or valve problems.
Report back, this is interesting.
Danford1

 

I had a very similar problem, 99 F250 V10 123,000 miles. Very rough idle, shuttering at lower rpm and slight acceleration, and like you it almost felt like a drive train problem. I also experienced terrible gas mileage, 7-8 mpg (before I was getting 12 mpg). I too was not getting a CEL. I replaced all plugs with new Motorcraft gapped at .054. I also replaced all COP's and the fuel filter, now the truck runs great. I haven't went through a tank of gas yet to calculate mileage but I have to believe my problem is solved. To avoid the high cost of COP's I purchased 10 Accels from Speed Unlimited on Ebay $240.00. I have recently been told these don't last but so far so good.

 

Thanks Danford1. I will try to do a compression test. Ironically that is the direction that I was going in when while installing the compression tester in the #2 cylinder, it pushed the helicoil the repair shop installed the rest of the way into the cylinder. What a pain. Glad I was able to get the thing back out again. I know low compression could cause the rough idle but could it alos cause the computer to read a misfire situation?

For what its worth, the COP's on 1 and 2 are both fairly new. I just replaced one of them and the other is new within the last 12 months. The COP on #7 was relocated from #8 which was not showing a misfire. I swapped the two and #8 still doesn't show a code so I don't think it is a COP issue.

 

Low compression can cause ALL sorts of issues. With today's computers and sensor, God only knows what will throw a code and what won't.

Let us know what the compression test revealed.

I heard Time-serts are better than helicolis. They can't go through into the cylinder like the helicoil did.
Here is info and video on them ++ Ford Spark plug Repair ++, ford spark plug blow outs, blow out spark plug ejection blow out, blown out spark plugs, ford stripped spark plug, ford sparkplug blow outs, ford spark plug blowouts, ford defects, ford spark plug repair ford, ford spark

Danford1

 

Well I finally got my truck back. I ended up taking it to a local shop and having them check it out. Turns out cylinders 2 and 3 had 0 compression. I am not positive but I believe it is a head gasket problem. Pulled the valve covers and everything seems to be working correctly. Given the mileage ont the motor and most of the rest of the truck, I opted to have a reman engine installed inlieu of trying to having heads rebuilt. With 250K on it, I couldn't swallow spending the money to do the heads and wind up with another problem 3 months down the road. If half the engine was going to have to come out, it made better sense to just go ahead and do the whole thing.

I am just happy to finally have my truck back on the road.