Ford_Assassin

iTrader: (4)

Hey guys I was out driving my Datsun Z (see sig for specs) yesterday and my fan relay died without me knowing so the car started to overheat once I got into some traffic. Soon as I got moving again it leveled off but I noticed it started to miss while under load (even a light load) and there is a noticeable loss in power during accel.

If its in neutral it idles and revs just fine, but soon as I place it in drive and load the motor a little while applying the brakes it will start to miss.

I checked for codes with my hand held scanner and there are none pending or stored. I started to worry about a possible head gasket failure, but there is no water in the oil or oil in the water. There is no unusual valvetrain noise either, but I haven't pulled the valve covers yet to check for sure either.

Tonight I went ahead and yanked all the plugs and all of them looked great except for #5 which looks like its starting to fowl. While I had the plugs out I figured I might as well check the compression on #5 which gave me 180 psi. I tested #1, #3, and #7 too and all were within 1-3 psi from each other.

So at this point I am thinking maybe it overheating was just a fluke and its either #5 spark plug, #5 plug wire, or #5 coil pack (all original factory stuff from 2005).

I bought another set of spark plugs, but the store was out of plug wires until Monday. I will go ahead and put the plugs in the morning and try my luck.

Any other suggestions on what it might be?

Thanks guys!!

ae13291

iTrader: (8)

seems like a dead injector. or possible coil ready to go bad? i had the same issue but it ended up being a cracked spark plug

Ford_Assassin

iTrader: (4)

I considered an injector being the issue, but you'd think the plug wouldn't be fouling and smelling like gas if the injector was dead or dying.

Still, I have an extra set of injectors that I can try if all else fails.

Could you see the crack in your plug after removing it?

I would be happy if mine ended up just being a bad plug too, but my luck usually isn't that good.

Thanks!!

ae13291

iTrader: (8)

my crack was in the porcelain itself. it was causing it to ground itself but at the same time it was tranfering some spark to the tip. when ever i had a cylinder misfire due to no spark the spark plug would be cluttered with oily residue. you checked for spark right? sorry i dident read your complete thread

Ford_Assassin

iTrader: (4)

Did you get any codes when you were having spark plug issues?

ae13291

iTrader: (8)

after driving close to 100 miles i had a check engine light come on for 2 minutes and it turned off by itself. it came up for a #4 cylinder misfire. i was pretty thank full for that light coming on because i changed lots of things trying to find the problem, i even hallowed out my cats thinking it can be clogged.

Ford_Assassin

iTrader: (4)

I was hoping you were going to say you didn't get any codes because I am not getting codes for mine......

ae13291

iTrader: (8)

if the problem just happened its gonna take some time for the sensors to really pinpoint it man, but the #5 cylinder seems like the culprit. check for vacuum leaks too.

ae13291

iTrader: (8)

seems like you have a cam too, its gonna be even harder for the engine to pinpoint further, i had my problem before my cam was done.

Ford_Assassin

iTrader: (4)

Yeah my cam does make somewhat harder to notice, but you can feel the miss causing a shake under load.

99 2500

Had the same symptom, miss under load only with no codes. Ended up finding a small tear on one of the spark plug boots ( MSD wires ), seemed to leak voltage under load. Actually saw it arc under load.

Zero4488

iTrader: (10)

Didn't read all the posts...not sure if this was mentioned swap the coil pack around and see if the issue follows it....

Ford_Assassin

iTrader: (4)

Okay, I borrowed a plug wire from a buddy and it seems to have taken care of the problem. I didn't even swap out the coil pack.

I am going to give it a few days before I confirm it was the problem.