very bad gas mileage

since I didnt get many replies last time, i'll go for it again

I got a 95 Miata w/ 30k miles.

Getting about 21 mpg... I use to get 25-26

All tires have 30 psi on all tires.. Just got my oil change Changed my air filter Put some fuel injector cleaners into my tank..

I dont know what to do... anyone have ideas?

-Sohel

Reply to
s0hel
Loading thread data ...

O2 sensor? EGR? Plug wires have more than 25k miles on them? If the wires are original yet I would bet that is your trouble. Replace with NGK plugs and wires. Any codes present? You can go to a place like Advance auto or Auto Zone and have them check for old code for free.

Reply to
Mike®

about the O2 sensor and EGR -- I dont know what that means.

I put in new spark plugs and wires 5000 miles ago

How do I check for codes? You said go to Autozone, but I dont know what the code is suppose to show..

-Sohel

Reply to
s0hel

Sometimes the right answer is the hardest to hear.

Sohel, you appear to have a legitimate complaint although it is not fully confirmed at this point. Mike Verive was on point in the last thread, "Too many possibilities, too little data to make too many comments at this point."

If you are saying that you were getting 25-26 MPG, then it dropped to 21MPG, then you did this type of maintenance/repairs that leads us down path 1. If the mileage drop happened after you did the maintenance then we go down path

  1. If you are on path 1 and you are trying to guess your way out of this, stop and take it to a competent independent repair shop that specializes in Japanese cars other than Honda's. (as a side note, Honda does things differently than all other companies and thus lessons learned with Honda's don't relate well on other cars). I also say to take it to an independent repair shop verses a dealer because most dealers (all dealers?) run 'flatrate' shops and diagnosing problems can be very unprofitable for the mechanic and he may try to sell the very profitable and expensive maintenance to you. I don't think you have the expertise to distinguish what maintenance is reasonable considering your complaint. Whom ever you take it to, do not hold back any information such as when the issue started (If you actually know) or what has already been done to try to cure this problem. Don't expect your mechanic to be a mind reader. Many people, when confronted with a 'poor gas mileage' complaint, bring their car in for a tune-up and are often confused and upset that the mileage is still poor. Sometimes the diagnosis is more expensive than 'throwing' things at it but at least you will know what it took to repair.

If you are on path 2 (this all happened after something was done you could take it back to them but only if you feel confident with the repair shop. Everyone can make a mistake and if they are competent they deserve to be given the opportunity to fix their problem. If they are a 'maintenance' shop that has no qualifications to diagnose this sort of repair please just take it to someone that can look over the work performed and rule out these issues.

Mike, don't take this wrong but taking this type of car to AutoZone and trying to solve a problem with a 'free' diagnosis maybe the costliest way to get your car repaired. What you may or may not know is what the codes tell you. They never tell you that a part is bad, they tell you that a reading is not within standards. It is up to the diagnostician to find out why. Many times, in fact most times, when a car actually shows symptoms of a problem, more than one problem exist. For example, the computer has built in redundancy, if a sensor says the car is running completely cold yet all the other reading act as though it is running at normal operating temperatures the computer will ignore the temp sensor reading and install a 'default' reading in it's place. Hence, a car that is running fine may actually have many problems. I have yet to hear of any single thing (expect a leaky fuel system) that will cause a 20% drop in actual fuel mileage. Remember, diagnosing out any type of problem takes longer than guessing, but sometimes guessing will fix the problem. I prefer to have most running problems diagnosed because of the repercussions down the road. Sohel, bad gas mileage is a problem, not just an inconvenience. It can cause expensive failure of the catalytic converter and other things and it can also be an expensive repair. Many times people suggest, in good faith, for you to get your maintenance taken care of first. Sometimes this will hide the problem. For example, bad spark plug wires will cause an engine skip (causing bad gas mileage) but bad coils can cause bad wires. By replacing the wires we only hide the problem until the coils ruin the wires again.

I hope some of this helps.

Sorry for the long post.

Fred

91 Miata B

"Mike®" wrote in message news:sI%Ua.55807$ snipped-for-privacy@twister.rdc-kc.rr.com...

Reply to
SC.RR

I felt all the rims and they all felt the same

I felt all the brakes (inner rims i guess) and they all felt hot (same temperature in all though)

-Sohel

Reply to
s0hel

I have done all the basic maintence routines to it , and the MPG gradually went down to an all-time low of 21. I have done oil changes every 3000 miles, flushed my fuel injectors every 6-7000 miles. I put a new air filter

200 miles ago, and 6000 miles ago before that. I got new spark plugs and wires and that made a steady 23-24 mpg, but still it kept lowering. My next guess is what you suggested below, the coils. My dad and I are going to try to replace that, we have the shop manual so I think we'll be ok.

If it is STILL giving me problems, i will take it to a mechanic for more inspection.

thanks for your help Fred, I'll let you know how it turns out tomorrow

-Sohel

Reply to
s0hel

I replaced the plug and wires 4000-5000 miles ago. and I did not notice any stickin caliper problems

Thanks for your suggestions though, I will take it to Autozone tomorrow and tell you the code

-Sohel

Reply to
s0hel

Why are you flushing the fuel injectors every 6-7000 mi. That seems extremely often with todays fuel formulations. Depending on the injector cleaner you are using, you may have prematurely deteriorated the injector seals. Leaking injectors will be a cause for poor gas mileage. If the leaking is only slight- moderate you will have rich mixture at idle and very low rpm which will disappear at high rpm. Timing and throttle air adjust can hide this pretty well, but gas mileage will show it. Only way I know to tell if they are leaking is out of car testing.

Reply to
Stephen Toth

The mechanic told me there was a lot of carbon build up, and he suggested for me to get my fuel injectors flushed, so I did. That was 6000 miles ago. I go to the mechanic again for my oil change, he said I have a slight carbon build up, so my dad suggested me to get Super High concentrated Fuel Injectors cleaners. To find a leak, can I just check under my car when I park to see if there are any fluids dropping?

-Sohel

Reply to
s0hel

Uh, how did this mechanic diagnose the carbon build-up? How did he see that carbon build-up? Did he look at your spark plugs?

Not for leaky injectors - when injectors leak, it means that extra fuel is squirting into your engine. It's internal. If it's bad, it might lead to carbon build up from running rich.

I can't help but wonder if you're being fleeced by the oil-change shop, or, worse, actually creating a problem.

Dana

Dana

Reply to
Dana Myers K6JQ

I dont know what he used to see the carbon build up, he just told me.

:\

-Sohel

Reply to
s0hel

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.