UPDATE: Missing/bucking -- something causing plug wear

[tankhokie]

ok, quick summary.

'96 X 302 with a hesitation/miss/stumble at low rpm and slight load on engine like a small incline.

i pulled out all my autolite plat plugs (fairly new) before a long trip this past weekend and found this:

bank 1 (passenger side cylinders)
all 4 plugs looked great with slight wear, still gaped fine 0.052-0.054

bank 2 (driver side cylinders)
all 4 plugs showed MUCH more wear, gaps were opened to around 0.062, the inulators seemed to have a worn (maybe hot?) spot on each plug (looked like a single round worn spot on the insulator) also a small amount of chaulk like deposits on a few of these plugs' electrodes.

so i cleaned and re-gapped. during our trip we noticed the problem (miss) went away. i couldn't make the miss come back. BUT then after a couple hundred miles, the miss is coming back, less, but still coming back.

SO...what do you guys think could cause the one bank of cylinders to cause advanced wear, strange deposits, etc. but not he other bank???

i know the coil packs are not divided by bank sides, but the O2 sensors are...i am getting no codes set, but wonder what can cause this condition??

thanks again

 

[MrShorty]

Here's a thought.
On newer engines (and I think the 5.0 is in this category), one bank of spark plugs is positive fired, the other is negative. Unless you are using "double platinum" plugs (where both the center and outer electrodes are platinum), one bank will show excesive wear like that. I would check your spark plug part numbers and cross references to make sure you have double platinum plugs.

 

[tankhokie]

mrshorty,

i know i have the wasted spark system on the X, but not sure about the negative/positive bank firing. i looked at the '96 5.0 firing order,

fire - waste
1 - 6
3 - 5
7 - 4
2 - 8
6 - 1
5 - 3
4 - 7
8 - 2

and see that the pairs get fired together (same polarity), so that makes me doubt that i have the plugs being fired by polarity. maybe the newer X's have banks being fired by different polarities???

good suggestion mrshorty, but is my reasoning correct here??

keep the suggestions coming!

 

[Iggy flywheel]

It could be your plugwires. MFI could be causing interuptions. Magnacore wires are great and reduce the magnetic force inteferance caused by other electrical equipement. There website has good info on this subject.

 

[tankhokie]

thanks iggy,

but my wires are new and the re-gapping solved the problem.

BUT what now is occuring (and probably did in the first place) is that the drivers side bank of plugs are wearing MUCH MUCH faster than the passenger side.

the wear is not normal wear (like the passenger side) but seems to have a "hot spot" (almost like a blister) on each of the insulators. the plugs are worn down and a white/gray ash-like deposit was found on the SIDE of some of the electrodes (the one you bend to gap).

it seems that something is causing that side of cylinders to do something different.....but what and how?

 

[Evicerate]

Keep in mind I have no experience in this, but I was reading up on the 4.0 OHV engines, and they have problem with the #5 plug getting build op and oil on the threads. This is caused by a loose intake gasket, allowing a vacuum leak. That causes that particular plug to get more air, run lean, and also hot?
I think that's right, so maybe you have a similar problem on your 5.0?

 

[tankhokie]

well, i checked my intake and valve cover seals and didn't find any leaks.

good suggestion. this one has me stumped again. i am pulling the plugs again now to check the #'s and see if they are double plats.

hasn't anyone ever heard of this happening before??