Last Saturday, I spent about 3 hours changing plugs on my truck. Bolted it all back together and took it for a test drive. WOT and hard acceleration were fine, but idle and 1/4 part throttle there was a distinctive miss.

Went back to the garage and unplugged and replugged all COPs, made sure all injector connectors were tight and checked for DTCs. No codes and the miss is less noticeable, but I'm still getting a sluggish feel off the line and sometimes the idle will drop to 350 or so RPMs before coming back up to 650.

I used Motorcraft double platinums gapped at .052.

Any suggestions on what else to check?

 

the dielectric grease?...try resetting your computer and take it for a nice drive,no WOT....you could have bent one of them putting it into the hole

 

I don't know about the Ford platinum plugs but I have noticed when using Bosch platinums they occasionally give a misfire for the first week or so and then run great after that.

Ian

 

Yeah, used the grease.
Don't think I could have bent a tip as I lowered the plugs into the holes with a grabber tool and even started in on threads before I put a socket on it.

I guess I'll try resetting my computer and driving again, but I was hoping to not lose the learning I gotten on my microtuner. If that doesn't work, I guess I'll have to take all apart again and see if there's an issue I can resolve.

If anyone has any other ideas, please let me know

 

I have seen the wire that supplies the electricity to the coil pack become freyed or pulled half way off and cause that problem. Its hard to detect because it's covered with plastic protector. This would probably be a close to last resort. Plug Gap OK? Just some thoughts.

 

Sounds like you cracked a plug. I hate to tell you to pull them to check, but that is what it will take.

 

you can try ohming the wires as you take them off one at a time

 

Not sure what you mean by "ohming the wire". Mine's a COP design.

Thanks for the suggestions. Sounds like I have another couple of hours work tomorrow

Is there anyway to "check" a plug other than visual inspection and resistance test from the firing tip to the connector?

 

I installed a set of Autolite Platinum Pro's which are the same pretty much as double platinums. They have a platinum centre electrode and a platinum disc imbedded in the outer electrode. Anyhow, I put in a set of MSD Superconductor wires at the same time, dielectric grease too. Had a misfire. Tried everything. Even sprayed some ammonia window cleaner on the wires (which usually will show you a bad wire in the dark). Checked the coil packs, etc. No problems.

Well, in the end I pulled those plugs out and put in a set of plain old Champion Truck plugs (copper core). Runs fine now.

I think every once in a while you get a defective brand new plug and only one of those bastards can ruin your day.

 

Y2kXLTSport -

I would go and purchase 1 new plug of the same type you installed.

Try and make a guess as to where the misfire is (left or right) and swap 1 plug with the new one. If it clears up, you're done. If not, move on to the next one.

Hopefully, you just have 1 bad plug and you'll get to it before you pull all 8... Although, if you're anything like me, Mr. Murphy will show up and really screw things up!!

Good luck and let us know what you find...

 

I haven't gone that far yet! lol

After rechecking all connections, etc. its not really a miss now.... more like a rough/low idle. Gas mileage seems fine (haven't finished the tank yet), but the idle will drop down to about 300 rpm when coming to a stop then go back up to 550-600.

Does this change anyone's ideas?

Thanks again

 

Also, is there any way to test a COP using a multimeter? What are the specs?

 

I dont' know about testing a COP but with spark plugs they can actually look ok, resistance test shows nothing unusual (from terminal to centre electrode) but when you fire 50k volts through them anything can happen. At that voltage it's simply a different animal.

If the idle is surging perhaps you knocked off a vacuum line somewhere? Is the intake on properly, did you hook the MAF and the other air inlet sensor back up properly?

 

I went and pushed all the connectors on tight(er), checked all the vacuum line, made sure that the injectors were just like when I started since i had to move the connectors to access some of the COP bolts, and put everything back on except the splash guard and the black box. I replaced the black box with hoses and it seems to be OK. I'm glad I'm not in the garage today or yesterday because its down around 30 degrees, raining/sleet/snow.

THanks for all the suggestions.... I guess mine was unique lol

If it comes back, I'll be trying to find a bad plug.

Any idea how long COPs are designed to last?

 

I have no idea. Probably not much longer than the factory spark plug wires on the 97-98's.

Personally, I don't think I want COP even though theoretically it's better. My tenant's 92' Mustang with the 4-banger has twin coil packs that look pretty much identical to the coil packs on the 97-98 V-8 motors. I guess it goes to show when you have a good thing don't mess with it. Perhaps Ford went to COP design to reduce plug wire failure within the new vehicle warrantee. After that they will gladly sell you COP units. LOL. They should have just used better quality OE wires.

Oh well. Happy truckin.