Engine Suspicious Spark Plug Scenario

joetrainer31

joetrainer31

15 Year Member
Mar 31, 2013
869
365
114
SC
#1
So I'm lighting up the message boards with some perplexing issues concerning a new to me 95 GT. One issue I have come across is a hesitation/stuttering/lethargy to the car. While checking out the ignition system components I observed that the cap/rotor seemed (not stock), but new. I replaced the plug wires, and was going to install basic autolite 25's when I noticed that they would not screw into the heads. Maybe it was my mishandling? Anyhow, the car currently has Champion RS14YC6 plugs. The Champion plugs have a much longer thread length than the Autolite 25's. I have 3 questions:

1. Could these be the wrong plugs?
2. Any clue why the Autolite 25's do not seem to screw into the heads?
3. What, if anything, am I missing?
 

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#2
It should have 25's. These are a list of plugs that your Champions interchange to however I would check to see what heads are on it.
Details about Champion RS14YC6:

  • Threaddiameter: 14mm
  • Threadreach: 17.5mm
  • Seattype: tapered
  • Hexsize: 16mm
  • Tipconfiguration: projected
  • Construction: Standard construction
  • Terminaltype: Solid
Possible spark plugs:

 
#4
gearheadboy said:
They actually fit a Cobra that year. Are your plugs angled or straight out?
Click to expand...
My plugs are angled now that you mention it. I'm quite perplexed over what the issue is. How do I check the heads w/o taking the thing apart? Would there be casting numbers visable? I have never owned a 5.0 that will not accept Autolite 25's or equivalent.
 
#6
RsStanG1987 said:
Maybe he has gt40 heads


Yellow Bear racing 2k13
Click to expand...
The thought crossed my mind because of the plug fit issue & because there is also an SVO intake manifold, and cobra tail wing. This mistery is killing me because the car runs like crap.

I did a basic KOEO run and the only code I got was for the fan, which demonstrated 2 speeds anyhow (clearing ECM now in case it was stored). I also did a KOER basic test and everything came back good. I then did a Cylinder head test and it scored perfect. I changed the fuel filter 1st thing & did a basic tune up.

I could sure use some wisdom/advice on the matter. And, what is "Yellow Bear racing 2k13"?
 
#7
joetrainer31 said:
My plugs are angled now that you mention it. I'm quite perplexed over what the issue is. How do I check the heads w/o taking the thing apart? Would there be casting numbers visable? I have never owned a 5.0 that will not accept Autolite 25's or equivalent.
Click to expand...
GT40P heads have a different angle than GT40/Cobra/Standard 5.0 heads.
View attachment 182727
gt40andPheadsplugs.jpg
 
#9
gearheadboy said:
GT40P heads have a different angle than GT40/Cobra/Standard 5.0 heads.
View attachment 182725
gt40andPheadsplugs.jpg
Click to expand...
Beautiful pictures! So helpful -thank you. The spark plug angle on the heads looks a lot more swept like the "GT" picture, but I will return once again to the car in order to check for a casting.

Side note: Even after clearing the ecm (battery unhooked 30min) I'm still popping a code 564 (fan control circuit failure) even though the fan demonstrates 2 speeds. I wonder if this somehow plays into the mix.

Question: should I look toward the front or rear of the head in order to observe the cast markings?
 
#13
gearheadboy said:
It sounds like you have GT 40 or Cobra heads. NOT GT40"P". That explains the spark plugs. The heads are the same L or R. The GT casting is in the rear on the other head. I have no idea on the code. Maybe google it.
Click to expand...
Gearheadboy,

I went with your prior instructions/information and bought plugs to fit GT40 iron heads (i.e. 764's). I have not tried to install them yet because I was busy addressing a 411 & 412 code by cleaning out the IAC, fixing its 2 exposed wires, and making sure it was properly secured to the TB -which it was not =vacuum leak.

Anyhow, you pictures and advice were invaluable! Thank you so much. Now I need to try and address the CCRM. I have a coolant fan circuit fail code. The fan displays 2 speeds w/a KOEO diagnostic, but for some reason it pops the 564 code. I'll take any thoughts you want to give, I have plenty of thoughts about the whole CCRM thing myself!
 
#14
joetrainer31 said:
Gearheadboy,

I went with your prior instructions/information and bought plugs to fit GT40 iron heads (i.e. 764's). I have not tried to install them yet because I was busy addressing a 411 & 412 code by cleaning out the IAC, fixing its 2 exposed wires, and making sure it was properly secured to the TB -which it was not =vacuum leak.

Anyhow, you pictures and advice were invaluable! Thank you so much. Now I need to try and address the CCRM. I have a coolant fan circuit fail code. The fan displays 2 speeds w/a KOEO diagnostic, but for some reason it pops the 564 code. I'll take any thoughts you want to give, I have plenty of thoughts about the whole CCRM thing myself!
Click to expand...
You are quite welcome. Please keep frequenting our forums. You can yourself be of help to someone. I'll do some research this evening and get back to you.
 
#15
gearheadboy said:
You are quite welcome. Please keep frequenting our forums. You can yourself be of help to someone. I'll do some research this evening and get back to you.
Click to expand...
Thanks again gearhead. I'd be glad to help anyone that has need.

I plan on pulling the CCRM today in order to get a part # and visual. I hear/read that when replacing the unit one needs to get the exact same one (e.g. part #, color of box, same large single letter code "R" or "S"). I'm anticipating your research results!
 
#16
joetrainer31 said:
Thanks again gearhead. I'd be glad to help anyone that has need.

I plan on pulling the CCRM today in order to get a part # and visual. I hear/read that when replacing the unit one needs to get the exact same one (e.g. part #, color of box, same large single letter code "R" or "S"). I'm anticipating your research results!
Click to expand...

Behold, the dreaded CCRM hath been pulled from mine car.

image.jpg
 
#18
RsStanG1987 said:
Idk if its the problem.. Mine went and caused all sorts of codes


Yellow Bear racing 2k13
Click to expand...
I'm assuming that its at least "a" problem due to the code that I pulled. It lead me straight to the CCRM. I purchased another one with exact part number and "R" code as my current (it all must match up to function properly). A friend of mine works on electronics for a living. When he gets some time he will completely overhaul my old one. Then I'll either have a spare or one to sell on ebay.
 
#20
RsStanG1987 said:
I diddnt know u had to match them I used a gt one on my cobra and had no issues


Yellow Bear racing 2k13
Click to expand...
Maybe you were fortunate? I did a bit of research that indicated that the part is used in several models, but that it must be matched exactly. Moreover, the rebuilder I bought it from only warranties it and commits to its proper function if you buy the exact part.

I could simply be wrong, but I didn't want to take the chance. Nonetheless, i'm glad that your replacement is working for you. I don't like electrical problems! lol
 
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