My '99 accord LX (4 cyl) has 95K miles. I changed out the spark plugs for the first time 3 wks ago with NGK brand, copper. The model I purchased was the exact same as the one recommended in the manual. I also changed the engine oil at the same time using Mobil 1, 10W-30.

I am now seeing a significant drop in the MPG. Over the past 5 years I was getting consistently 450 miles per tank (freeway miles), but over the previous two tanks since the plug change, I am seeing 325-350 miles on the tank. Huge difference!

Is this due to the spark plugs not being gapped correctly? I thought the NGKs are pre-gapped according to factory spec. Also, if I switch the plugs to the Iridiums, will that solve my problem? I read they are designed with a more forgiving gap distance.

btw, my air filter is only 2 months old, and the tire pressure is normal (34psi). my friends say the mpg drop could be caused by the oxygen sensor, fuel filter, spark plug wires and/or distributor cap. but i think the main culprit are the plugs.

Any advice will be just great...

 

did you set the gap right on the plugs or were the gaps preset?

 

I also have a 98 accord 4-cyl automatic with132k miles.
1) First, you should have replaced the plugs every 30k miles not at 95k miles. Those plugs probably looked terrible.
2) You did the right thing by using the exact NGK factory plug for your car. Yes, most NGK plugs are pre-gapped. So that is probably not the problem.
3) Lower your tire pressure to 30 psi (cold pressure) on all tires as recomended on the door panel.
4) any check engine lights? My o2 sensor went out at 80k and my catalytic converter went out at 95k. These are common problems with this vehicle that can cause poor mileage, but a check engine light should have gone off.
5) Fuel filter is inside the tank. (not the problem).
6) If i were you i would replace the distributer cap and roter butten, but reuse wires.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Elvis1977 &raquo;</TD></TR><TR><TD CLASS="quote">I also have a 98 accord 4-cyl automatic with132k miles.
1) First, you should have replaced the plugs every 30k miles not at 95k miles. Those plugs probably looked terrible.</TD></TR></TABLE>
I doubt if plugs would last 95k miles and he probably did not buy the car new.

 

answers:

1. I didn't check the gap size of the new plugs. I assumed they were already gapped correctly out of the box. Could they be off?

2. I did buy the car new... in hindsidght, should've replaced the plugs sooner.

3. Check engine light hasn't come on.

Q: should I try the iridiums? they're supposed to give me better gas mileage, so they say.

Thanks-

 

According to honda, spark plugs do not have to be changed until 160K.

Spark plugs, before installation, must be checked for correct gap... THey are not gapped at the factory.

It is possible, as i have seen on other cars, that some plug desings will actually cause your engine to suffer from performance. I have seen a car come in to my shop, where those iridium plugs were causing hesitation... WHy, i don't know.

My suggestion is to remove the plugs, regap according to spec and re-install. Drive around for about 2 weeks and check gas mileage. Then if it is still low compared to the previous plugs, then replace them with oem.

fs

 

[QUOTE=filthy_shovel]According to honda, spark plugs do not have to be changed until 160K

WTF you really believe that ? Even the pricey iridium plugs max at about 50-60k
It's the same type of argument with oil and trans fluid change schedules they are bluesky.
A basic NGK or Bosch plug life is 20-30k miles. Plugs are cheap considering milage /gas prices. Have a read:
http://hostingprod.com/@aa1car...6.htm
http://www.spark-plugs.co.uk/p...s.htm


Modified by alotawatts at 12:48 PM 2/10/2005


Modified by alotawatts at 12:50 PM 2/10/2005

 

Actually, for '99s, the V6's plugs will are supposed to last to 105k or so miles. (platinum plugs) And yes, I have seen plenty of platinum plugs last well past 105k miles.

The 4-cyls, however, used copper plugs, and Honda recommends changing them every 30k miles.

There was no 160k mile interval for 6th gen Accords. At all.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by philadd &raquo;</TD></TR><TR><TD CLASS="quote">Actually, for '99s, the V6's plugs will are supposed to last to 105k or so miles. (platinum plugs) And yes, I have seen plenty of platinum plugs last well past 105k miles.

The 4-cyls, however, used copper plugs, and Honda recommends changing them every 30k miles.

There was no 160k mile interval for 6th gen Accords. At all.</TD></TR></TABLE>

Could be, my mistake, i was using the 2002 civic maintenance program for reference. THey say to replace every 176,000 km as it is a fuel injected engine and since timing, fuel mixture and such is always optimal, plugs don't "wear outW as fast as the old carbed or FI engines....

fs

 

I've noticed over the years that the NGK's that come out of the box from the store are pretty close if not exact to the correct gap. I will bet money that NGK gaps their plugs at the factory. That's not to say that a spark plug could have been dropped or bumped before it got into your hands. If I were you I would not use the Iridiums. Instead, go and buy 4 more new OEM NGK plugs from Autozone, check the gap and install again. They are really not expensive. By the way, is your car an automatic like mine? If so the gas mileage on our car is 23/30 (city/highway). The tank holds 17.1 total gallons. So now you calculate. I think 350 is about right in the city, but not for the hightway. 17.1x23=393 (maximum number of miles); 17.1x30=513 (maximun number of miles). Hope this helps.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by filthy_shovel &raquo;</TD></TR><TR><TD CLASS="quote">

Could be, my mistake, i was using the 2002 civic maintenance program for reference. THey say to replace every 176,000 km as it is a fuel injected engine and since timing, fuel mixture and such is always optimal, plugs don't "wear outW as fast as the old carbed or FI engines....

fs</TD></TR></TABLE>

It's not your mistake. It's the f*ucking manufacturers feed the stealerships plan.
Maybe it's a Communist plot ?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by filthy_shovel &raquo;</TD></TR><TR><TD CLASS="quote">

Could be, my mistake, i was using the 2002 civic maintenance program for reference. THey say to replace every 176,000 km as it is a fuel injected engine and since timing, fuel mixture and such is always optimal, plugs don't "wear outW as fast as the old carbed or FI engines....

fs</TD></TR></TABLE>

To be honest, I've never really followed the recommended intervals from Honda. My original plugs were still in the car after 100k, and there was no noticeable loss of power, or gas mileage... no stumbling, hesitation, excessive idle vibrations... Nada. I just finally decided to change them out...

But yeah, to the original poster, the first thing I would do is recheck the gap, and like Elvis1977 said, I wouldn't use the iridiums. Just stick with the NGK coppers...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by alotawatts &raquo;</TD></TR><TR><TD CLASS="quote">

It's not your mistake. It's the f*ucking manufacturers feed the stealerships plan.
Maybe it's a Communist plot ? </TD></TR></TABLE>

"feed the stealerships plan"?
If Honda says you don't have to change them for a longer period of time, wouldn't that mean the dealerships would make less money, since people wouldn't be bringing their cars in for tune-ups as often? So yeah, your comment makes no sense to me.

 

Sounds like you have a bad plug. Seen this before but never with NGK. Put the old plugs back in and if the milage goes back to normal you have one or more plugs that are bad.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by philadd &raquo;</TD></TR><TR><TD CLASS="quote">

"feed the stealerships plan"?
If Honda says you don't have to change them for a longer period of time, wouldn't that mean the dealerships would make less money, since people wouldn't be bringing their cars in for tune-ups as often? So yeah, your comment makes no sense to me.</TD></TR></TABLE>
Then think a little longer...
It's a well known fact that dealerships make most of their money on trade-ins and service. Technology has come along ways in auto design and manufacturing as well as synth-oils etc but some things are still old school.
I'm convinced most of the time if people don't do basic simple maintenance like plugs, fluids and filters at realistic intervals they will end up bringing their car in for service....major service. I would really like to see a plug thats never been re-gapped or cleaned with 100k + miles on it. I am not saying it's impossible especially as well as Honda and some other makers engineer things and thank you for adding 'crook' with stealership.


Modified by alotawatts at 2:41 PM 2/10/2005


Modified by alotawatts at 2:45 PM 2/10/2005

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by alotawatts &raquo;</TD></TR><TR><TD CLASS="quote">
Then think a little longer...
It's a well known fact that dealerships make most of their money on trade-ins and service. Technology has come along ways in auto design and manufacturing as well as synth-oils etc but some things are still old school.</TD></TR></TABLE>

I fail to see how these statements have any relevance as to how longer tune-up intervals lead to major problems.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by alotawatts &raquo;</TD></TR><TR><TD CLASS="quote">
I'm convinced most of the time if people don't do basic simple maintenance like plugs, fluids and filters at realistic intervals they will end up bringing their car in for service....major service. I would really like to see a plug thats never been re-gapped or cleaned with 100k + miles on it. I am not saying it's impossible especially as well as Honda and some other makers engineer things and thank you for adding 'crook' with stealership. </TD></TR></TABLE>

Okay, there were 2 of us in this thread who have already said we have gone about 100k on COPPER plugs. The 105k intervals are for PLATINUM plugs. And yes, platinum plugs do last that long.

You're going to need to come up with some better explanations, because honestly, all I see nothing but assumptions in regards to the spark plug issue becoming a "feed the stealerships plan".

 

Okay true probably no direct link with plugs and dealers. Jumping off the spark plug soap box now........I am not from the show me state
Whisper here (anybody have a pic of a 100k plug ?)



Modified by alotawatts at 7:15 PM 2/10/2005

 

Elvis1977,

Thanks for the reply. I'll follow your advice and pick up 4 more NGKs. It could very well be a bad plug. I drive 25 miles to work each way, all freeway miles. My driving habits have not changed, but I definitely used to get more than 400 miles per tank. Jus t doesn't add up. Just finished up the second tank today, and ended up with about 330. I will take a picture of my old plugs (95K mi) and post it...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by alotawatts &raquo;</TD></TR><TR><TD CLASS="quote">Okay true probably no direct link with plugs and dealers. Jumping off the spark plug soap box now........I am not from the show me state
Whisper here (anybody have a pic of a 100k plug ?)

Modified by alotawatts at 7:15 PM 2/10/2005</TD></TR></TABLE>

I will have some soon for ya. I am up to 96,000 km on my original set of plugs for my car, another 50,000 km and i will change them...

Hell, sparkplugs on my harley davidson shovelhead last longer than 30,000 km.

fs

 

Why the hell wouldn't you change the sparkplugs? For the price you might as well replace them once a year.

 

Schmitey,
They are talking about platinum plugs that truely do last along time. I thought most people in this forum liked to wrench a little bit and you would think with carbon build up etc they would swap 'em at least by 50k. I'm not faulting them but using the stealership stirred things up.

 

First thing I would do would be to put in all new plugs, OEM plugs, don't go for the fancy ones. I would also change your plug wires out with decent replacements.

Next, see what else you are overdue for on maintenance, if you changed your plugs 65,000 miles too late, how long as it been since your last brake fluid change, etc?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by alotawatts &raquo;</TD></TR><TR><TD CLASS="quote">Schmitey,
They are talking about platinum plugs that truely do last along time. I thought most people in this forum liked to wrench a little bit and you would think with carbon build up etc they would swap 'em at least by 50k. I'm not faulting them but using the stealership stirred things up.</TD></TR></TABLE>

I know many people who HATE the NGK platinums. The coppers do much better, are substantially cheaper, and last longer. Nothing against those people, but if you want to have 150k miles worth of carbon on your plugs go for it! Change your air and fuel filter at the same time, you wouldn't want to get good gas mileage or anything.