'87-'90 Renix 4.0; What plugs are you using?

[AJPulley]

For those of you who own a 1987-90 4.0L, what spark plug are you using? If I recall, the original specified by AMC (Chyrsler for you '88-90 folks) is a Champion RC9YC.

• If you're using something else, please explain why you chose it.
• Do you run a hotter or cooler plug?
• How many miles are you experiencing between inspecting/replacing the set?

 

[joe_peters]

NGK 7373; based on a lifetime of automotive service & repair they have been the most consistent in quality I have seen.

OEM heat range

Factory service interval is 30,000/15,000 (normal/severe); I seem to change mine about that interval.

 

[PacificEd]

I'm going to change my plugs for the first time and I went with the Champion RC9YC. They seemed to be recommended the most often.

 

[joe_peters]

I'm going to change my plugs for the first time and I went with the Champion RC9YC. They seemed to be recommended the most often.

They were the OEM plug, you may find the Champion 344 Copper Plus more commonly available.

 

[Ecomike]

I have an 87 and 89 Renix, about 100,000 miles total between them using Autolite single platinum, AP3924. Been using them for over 7 years. I have gotten well over 50,000 miles on them with little sign of wear.

289,000 miles on the ODO on the 87.

 

[xjtrailrider]

I run the NGK V-power plug in all of my XJ's and MJ. I don't remember the part numbers for the RENIX or the HO

 

[MaxxXJ]

I went V powers as well, they seem to do the job

 

[Johnnie Walker]

I typically use the champion coppers. Have used ACDelco equivalent.
For my current heep, when I did a tune up on it shortly after I got it, I used the plugs that came in the accel super-tune kit. Seemed to work good. Last time I changed the plugs I used the champion coppers.

 

[cruiser54]

NGK all the way. All my 4.0s have them.
Factory recommended replacement interval was 30,000 miles. We also replaced the cap, rotor, and wires at 30,000 at the dealership because it seemed the wires would fail before the 60,000 replacement interval if we didn't.

 

[Shorty]

have been running the AC Delco equivalent since 2007 in the '88. This is only due to them being discontinued in my store and a very good price because of it.

I've seen 3 years out of them twice and neither time were they even close to worn out or needing replacement-- just seemed to be the thing to do after pulling them to check. All cleaned up and ready for more service!!

 

[Johnnie Walker]

have been running the AC Delco equivalent since 2007 in the '88. This is only due to them being discontinued in my store and a very good price because of it.

I've seen 3 years out of them twice and neither time were they even close to worn out or needing replacement-- just seemed to be the thing to do after pulling them to check. All cleaned up and ready for more service!!

Last I saw the Delco's they were avaiable for about 1-1.50$/ea not bad for a good quality plug.

 

[Shorty]

yeah-- just stopped marketing that one at my store due to slow sales volume. I think mine were $.25 each when I picked up the remaining handfull and stashed them away.

 

[PacificEd]

They were the OEM plug, you may find the Champion 344 Copper Plus more commonly available.

Joe,

I went and looked at the plugs this morning and they are dual marked with both 344 and RC9YC on the end of the boxes. You are correct in that the 344 number seems to be the one they are using now.

 

[PacificEd]

What would you guys gap the plugs at (just to be sure I get it right)?

 

[GSequoia]

RCY9C, factory gap (don't recall offhand, should be printed on your emissions label.)

 

[Shorty]

RCY9C, factory gap (don't recall offhand, should be printed on your emissions label.)

.032-.035

 

[Ecomike]

LOL:

joe_peters :Listen to Shorty--he has spoken wisely
Ecomike :Listen to Shorty--he has spoken wisely
X2

I shoot for about .034, spec is .035 IIRC

 

[joe_peters]

LOL:



I shoot for about .034, spec is .035 IIRC

Did you notice I got "top billing"?

 

[sandsgg]

???

 

[2001JeepXJNS]

NGK all the way. All my 4.0s have them.
Factory recommended replacement interval was 30,000 miles. We also replaced the cap, rotor, and wires at 30,000 at the dealership because it seemed the wires would fail before the 60,000 replacement interval if we didn't.

Same here