i have an on 03 max 6 speed with 120k it has a very slight misfire at idle i think plugs. a check engine light came on then went away, i think its due to the plugs, havent been able to check the codes yet. but the problem is i drive 50% city/hwy and i only get about 220-240 per tank. is it probably because of plugs?

 

you don't gauge mileage by the tank. Reset the trip odometer, drive for a tankful, refill the tank. Divide the number of GALLONS used into the number of MILES driven. This will give you your MPG.

could be plugs, do you know when they were last changed? If not, be a good idea to change them. NGK double platinum are highly recommended unless you're supercharged or something...they'll last you 100k miles no problem.

 

yeah i was just gauging by the trip screen i reset it everytime i fill up. and i filled up sunday night and drove according to the trip reading 87 miles and im at half a tank. and i dont know when the plugs were changed i just bought the car, but i would assume never. and i just bought bosch iridium plugs, planning to get done within the next week or so.

 

As americaner said...to gauge your MPG accurately you have to calculate by miles driven, not tank level.

As far as your problem check the codes. You may still have a latent code even though check engine light is not currently showing.

But,,,if you are misfiring it is likely either your plugs, ignition coils, or both. Ignition coils are a pretty common issue. That's why it is important to read the engine code because it can tell you the specific cylinder(a) that is misfiring.

Another way to test for misfire is disconnect one ignition cool at a time and check for any changes. If no change then that's your bad cylinder.

 

1. Scan the codes and see if there are any.
2. Pull out one of the front plugs (they are very easy) and take a look at the condition of it. If the front ones look bad and/or the wrong type of plug, there is a good chance the rear ones are the same. In that case change the spark plugs.
3. After you make sure the plugs are good or change them, reset the codes and drive. If the check engine light comes up again, scan the codes and see which cylinder misfires.
4. Swap coils around and see if the code changes to another cylinder. This means the coil on that cylinder is bad. In that case you replace it with an OEM coil and you call it a day. Unless your wiring or ECU is bad, but that is very unlikely.

Hope that helps.

 

yeah i got my code pulled last night it came up as p0300.

 

General misfire code which is too bad because it doesn't lead to any specific cylinder or cylinders. If you have some cash consider replacing all of the spark plugs and see if that corrects it. If not, you'll have to do some further investigation by unplugging coils one by one while the engine is running to see how it affects the misfiring.

As I described in my earlier post, if you disconnect a coil and there is no change in the misfiring then that is your bad coil. You could also have multiple bad coils.

If you do have bad ignition coils DON'T buy aftermarket, go with OEM. Aftermarket ignition coils have been known to be problematic. I would suggest you check out http://www.nissanpartsasap.com/?siteid=216643 as they have great prices.

 

i actually already bought the plugs, bosch iridium. i plan to take it to pep boys to get it done they are charging me 240 for plug replacement only. is that fair? i dont have the time to do it myself due to my work schedule.

 

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