I have a 1990 Convertible with 92000 miles I recently installed a RB Header along with a Mazadatrix high flow cat. I replaced my O2 sensor and plugs and fuel filter. I am only getting 10 to 12 MPG in town HELP!
My clutch needs replacing as it is not as grabby as it should be, could this have anything to do with the poor fuel economy?
I know our cars were rated by the EPA at 17 city and 24 highway but 12 is a far cry in the city when I am shifting between 3500 and 4000 RPM

 

this is my thing, but try shifting below 3500 RPM. I think, correct me if I am wrong, that the secondary injectors kick in above 3500 RPM. Try that.

 

wow thats awful!

notice any smoking at all while driving?

try checking/cleaning your air filter.. maybe (im not sure on this one) you should upgrade to a cone filter to compliment the exhaust setup.

also make sure your sparkplugs/coils are all in excellent order.

 

an n/a 13b should be getting better MPG, even if he was shifting @ 6k every gear..

 

I have a K & N cone Filter and my coils all are with in spec.
Also no smoking!

 

oh, ok. good to know.

 

hmm.. how old are the spark plugs?

hows your fuel filter?

 

Less than a month on both parts!

 

faulty injectors maybe?

im almost at a loss here! i can only cover the basic stuff! we need a guru here!

 

I am about 30 miles into a tank with injector cleaner added hope that helps.

 

hmm.. depends on the stuff.. personally i have added FI cleaner a few times and never noticed any change.

some people around the board have noticed a signifigant MPG difference when using a 'canadian tire' (which is our big auto parts supplier.. its the equivalent of your biggest auto parts chain store) anyways a canadian tire product that is FI cleaner that comes in a tin canister..

im not sure the actual name of it.. i should see if i can find it for you..

 

I used a FI product recomended on the Atkins site so I hope it works. It was also in a tin canister thank you for the offer.

 

wow.. it looks like your on the right track!

someone will see this and post a reply.. otherwise for the time being i cant think of anything else to check.. yet..

 

what is the FI product recommended by Atkins?

 

Well looks like my leading coil was bad I hooked up a timing light to it and nothing happened I then hooked up the light to the trailing coil and the light worked.
My car was running great on only 2 of the 4 plugs but I think it explains the poor MPG. I cant wait to see how much better the MPG is when the coil is replaced.

 

I installed the new leading coil and bam do I have some power now. I have owned this 7 for about 2 months and was thinking the car had good power but used a lot of gas! Also I could smell a lot of un-burnt gas in the exhaust on idle that was due to only the 2 trailing plugs working. It is nice to have all 4 plugs firing again. I will post in a few weeks and tell you all how much the MPG has gone up!

 

good job. Guess wat i'm going to check now? I get around 16MPG, and it sucks *****.

 

No 16 MPG is good in the city our car's are rated to get 17 MPG city and 24 Highway by the EPA test standards.
So if you are getting 16 MPG city you are only 1 MPG off test standards of a brand new RX-7

 

16mpg city driving is not very good compared to almost any other production cars... I still average about 220 miles per tank (70% city/30% highway)

 

if your tach works, chances are your trailing coil does too.

Try changing the plug wires first, just swap them with the leadings.



My car has been getting AWFUL gas mileage.. I just changed my o2 sensor and replaced my trailing coil (it died entirely) .. and it seems to be... EVEN WORSE! wtf.
I really need to figure out the problem, I've spent like $500 on gas allready this summer... I don't think I spent $500 on gas ALL last summer.

 

my 87 T2(S5 J-spec engine) 12 miles/gallon on highway

I also want to know why??????????????

 

If you think that 16 MPG city is bad than you should have done your home work before you bought a RX-7.
No one said sports cars were economical to drive just fun!
Here is a link to find out what the government test standards for any car by year make and model.
http://www.fueleconomy.gov/feg/findacar.htm

 

Mechanically, if you have bad mileage, you should look (in order) oil weight and condition, spark plugs, spark plug cables, air filter, gas filter, leaking injectors. In addition if you have good highway mileage but crappy around town, the O2 sensor, and air pump (if you have cats still).

And you can not clean a leaking injector with something that you drop into the gas tank, or pump through a vacuum line. You need to remove them and professionally clean them ultra-sonically with the proper solvents.

And the coupes got typically 17 city 24 highway MPG new. 'verts and turbos un-officially dropped to about 16 city and 23 highway.

 

I noticed a slight increase in mpg when I installed my HI-6 ignition amp. on my n/a 90. And if you guys are in need of one, let me know. I have one wired up to a s5 coil. So all you have to do is remove your coil/spark plug wires, mount the HI-6, put some power to the box, ground it out, install the new coil and put the spark plug wires back on and your good to go. Let me know if anyones interested. (End sales pitch. ) CJ