Civic VX & CX Spark Plug Gap
 

I have been doing some research into Platinum and Iridium spark plugs for my VX, unfortunately I am coming to realize there are none made

However in my search I have found that the Denso website (DENSO SPARK PLUGS)

Has the plug gap for the D15B8 (CX) and D15Z1 (VX) @ 0.032" instead of the regular 0.044" for pretty much every other Honda Civic D series engine, except for the GX which is a natural gas D Series engine that runs a compression ratio of 12.5:1 !

NGK has the gap @ 0.044" for the CX & VX.

I also checked plug gap on a 1988 Toyota Celica All Trac Turbo is 0.032 on both NGK and Denso (O.E. for Toyota)

A regular 1988 celica is a 0.044" gap


To sum it up I believe that Denso has spec'd a tighter gap on the VX, CX, and GX is because of high EGT in running Lean Burn mode and Natural Gas in the GX's case.

I only have 10k KM on a set of NGK's in my VX which I gapped @ 0.044 but I may check my gap and regap if necessary on the low side of 0.044"

Cheers!

I've always run NGK-V power plugs (OEM) in my VX and gapped them at the standard 1.0mm (±.1) with no problems.

I wouldn't recommend running platinum or iridium plugs in the VX as they have issues with the heat generated from lean burn. not to mention, those type of plugs don't even really run in the proper heat range for the VX ZFR4F-11

I have heard some horror stories about Bosch Platinum plugs breaking down and loosing a side or ground electrode. Although I did run Bosch +4 Platinum plugs in my Escort 1.9 EDIS engine and it seemed to run alot better.

When I first bought my VX some silly dilly had ZFR5F-11 plugs in her and a 1/2 clogged PCV valve, the cat also was completely plugged.

For some cars those fancy plugs do work better

you wouldn't believe how common that is for the VX. Mostly due to the parts store's computer not having accurate information. My VX ran like complete dookie when it had the 5 heat range plugs in there from the previous owner. The EGR system was clogged as well as the Cat Converter was falling apart. the Previous owner told me that he usually got 260 miles out of a tank when he owned it. :eek:

CROSSING FINGERS!!!

i just bought some NGK V-power ZFR5f-11 for my VX swap. It had the crappy Bosch Platinums in it that you said suck. Hoping this will up my power on highway driving in lean burn to stay in it longer.

Just drove 1.62 miles home from advanceauto, got 53mpg. :) (That is if these injectors have the same pulse as the previous motor. I thought both were 240cc. I hope honda didn't change the injectors, cuz i'm happy with 53mpg in town. Just gotta figure out this highway problem.

Good to hear you got rid of those Bosch plugs.....but the VX runs best wtih NGK V-Power ZFR4F-11 spark plugs. Would you be able to bring them back and exchange?
VX/CX injectors are supposed to be 190cc, this is another thing that can get confused a lot in the parts stores about the VX. Unfortunately there aren't any correlating part numbers I've seen to be able to tell what size an injector is on Hondas yet.

Sorry to be the bearer of bad news, but hopefully you can get the right plugs, that will help a lot with the hesitations.

Ha ha! I mis quoted the box. I bought the correct zfr4f-11 plugs. Had my gf check for me at home.

I'm bumbed about the injectors though cuz it probably means my Mpguino is off. And I'm probably getting worse mileage.

Ok good to hear, I had hoped that was the case. :thumbup:
There is some general settings for the MPGuino specific to the VX in the Wiki, I believe that you can double check. The mileage hit shouldn't be bad at all if there is any difference.

Gas mileage difference was calculated to be about 5% from what I had calibrated my DX motor to. NOT BAD considering after setting the mpguino to the VX wiki spec for injectors, i just got 49mpg on my 20 mile test tonight.

To whomever reads this thread with a d15z1, BUY NEW PLUGS before throwing money at any other parts when trying to diagnose poor gas mileage or lean burn to normal transition "hesitation"

Plugs cured my problem.

Here is the spark plug section from the service manual.