NGK OEM spark plugs bad - Bosch platinum plugs good???? - Fuelly Forums

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Old 10-12-2007, 04:57 PM   #1
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NGK OEM spark plugs bad - Bosch platinum plugs good????

Okay amateur gassavers mechanics, I've got a real brain twister for y'all.

I have been running Bosch platinum spark plugs in my 92 VX for a year and a half now with no problems whatsoever.

Due to the rave reviews in this amazing forum, I went out of my way to purchase the OEM spark plug for my car - NGK ZFR4F11.

After installation the following happened within one week of use:

1) Engine idle rpm dropped by 50 to 100. I adjusted the idle up to the 600 rpm nominal from whatever it was with the idle adjust screw.
2) Immediately started to experience a rough idle - seemed like on one cylinder. I refused to increase the idle more to smooth it out since I shouldn't
need to do that on a Honda!
3) Engine rpm at crusing speed in 5th gear at 70 mph went from 2200 to 2400.
4) Check engine light came on (code 48 - LAF sensor) when driving in 5th gear at 55 mph.

I took out the NGK's and put the Bosch platinums back in which have been in the VX for 30,000 miles. The following happened:

1) Engine idle rpm 700 so turned the idle screw back to original spot.
2) Smooth idle at 600 rpm
3) Cruising speed rpm back to 2200 at 70 mph
4) No check engine light since return to Bosch plugs.

Here's my take on why I started to have problems with the NGK's

1) The voltage requirement is higher on the NGK. For whatever reason I was getting a misfire on one of the cylinders because the distributor could not deliver sufficient voltage for some reason causing the rough idle and increase in rpm at the same velocity.
2) I got a bad spark plug - the weld on the c-shaped electrode was lousy on all four plugs. Did NGK outsource their spark plug manufacturing to China - EGAD!!!!! That would at least explain the rough idle - by that I mean I could see the engine shake like it was about to stall.
3 and most likely) Something is amiss that will give me trouble pretty soon. The platinum spark plugs are only buying me some time.

What do you think? The VX has 165,000 miles now.
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Old 10-12-2007, 04:59 PM   #2
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I always use NGKs because the consensus I have picked up over the years is that bosch is crap...iono what's going on with your car though. Sure you got the right kind of plugs?
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Old 10-12-2007, 05:04 PM   #3
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Yeah those are the exact OEM plugs. You are really quick, SVOboy *super shrug*

I didn't have time to add that the Bosch plug might be a little colder than the NGK. And I'm not bulls***ing in the least here - my VX did not like these four plugs for some reason.
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Old 10-12-2007, 05:05 PM   #4
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Indeed, that's very, odd. Especially since a stick shift shouldn't have engine speed change for the same gear and same speed...
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Old 10-12-2007, 07:03 PM   #5
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Quote:
Originally Posted by SVOboy View Post
Indeed, that's very, odd. Especially since a stick shift shouldn't have engine speed change for the same gear and same speed...
truth.

i have always ran ngk v-powers. we are talking years of owning hondas. did you check the gap?? how old is the dizzy?
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Old 10-12-2007, 07:27 PM   #6
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Yes, I gapped them. The dizzy is probably original.

But why do the "crappy" Bosch plugs work? That's the question here. If the NGK plugs were good there should have been no perceptible difference.

Seems to me that my old VX either can no longer handle a "hot" plug or one of the new plugs was just bad out of the box.

I should have taken a photo to show one and all that the weld quality on the outer electrode was really poor. I'm not saying with certainty that
this was the smoking gun but the weld should have been cleaner than it was. With a bad weld, the plug has too much resistance hence the spark might not occur under some circumstances causing a misfire.

I have no doubt that the NGK plugs when in good condition work great. Just not for me this time.
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Old 10-13-2007, 06:34 AM   #7
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i believe you i am just trying to find out why they are so bad. maybe the ngks are just a bad set or something? i dont know

how is the gap on the Bosch plugs? if it is tighter then i suspect that the dizzy is going bad, but it didnt have an effect on the bosch plugs.

are there any other electrical issues?? how are the plug wires? how are the grounds? ive got a couple other theories as to why the ngks would not work...

how are the boschs looking now? white, black etc?

OT: probably the best ground i ever did with my d16z6 was grounding the dizzy directly to the battery.
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Old 10-13-2007, 10:06 AM   #8
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bosch is crap... +1 i've had noting but problems with bosch in many different vehicles, ngk all the way!!!! don't give up on the ngk plugs your problem is probably elsewhere cause most vx's out there are running them (the oem ones) and they are running fine like mine
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Old 10-13-2007, 10:27 AM   #9
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I agree with you guys - in principal. But the problem I had with the NGK's still awaits an answer. I put new plug wires in the same time as the distributor cap and the Bosch plugs in March 2006. I

More details - the bosch plug color is light brown as it should be. The NGK plugs weren't in long enough for deposits. The Bosch plug gap is the same as NGK - 0.044 inches.

My VX doesn't have any running trouble at all - when I punch it this little 2000 lb car moves and quick! Too bad I can't do it that very often since my mpg will drop to 40 or lower. But when you rev this D15Z1 engine it will go - no hesitation. I had to outrun a jerk with a 90 something Buick Century because he wouldn't let me merge in. No problemo.

The VX is in as good a mechanical shape as any 16 year old car with 165,000 miles can be expected to. My 99 Buick Lesabre and my 2000 Chrysler Voyager are junk compared to the Civic and each has lower miles than the Civic.

I'm not bashing the NGK plugs - I just want to know why they didn't work right.
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Old 10-13-2007, 10:31 AM   #10
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Quote:
3) Engine rpm at crusing speed in 5th gear at 70 mph went from 2200 to 2400.
I think your clutch is slipping o.0
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