Hurley182BC

Ok here's the skinny of the entire situation:
I just bought my 8 last week. 04 GT everything but Navigation black leather, titanium gray. 28k miles on the odometer(I couldn't believe it either).

Problem #1 was really stupid. CEL was on. no power on accel. so i pulled it into our shop and raised it up to have a look. #1 rotor's leading spark plug wire wasn't even on the damn plug! wtf? So i pulled them, saw they were fouled bad, and put new ones in (NGK OEM) and figured new wires since they were original. checked the air filter: some sort of nest in there from it sitting a lot i guess. so cleaned it out and dropped a k&n in it. all is well again, until...

Problem #2 is still pissing me off. 24mpg my ***. 18 mpg my left nut. i'm averaging 15.6 on 16 gallons of the good stuff. 215miles of 80% freeway driving? ummm no. I put our generic scan tool to it and it says nothing that would indicate a problem.

CEL is on again as of my drive home tonight. seems to be running smoothly, no affects on power or anything. so since i'm the newbie to rotary tantrums, can someone throw me a rope? and educated guesses? theories? prayers or chants?

BTW...i still love the hell out of this car. its god in car form

alz0rz

iTrader: (41)

see sig, gas mileage sounds right and about the CEL, just get it read and go from there.

lateralus

iTrader: (1)

For the CEL... Since the car is driving fine, it would be really hard to guess what it might be. It could be just about anything... So like alz0rz said, just go get it checked then do whatever needs to be done or come back post the code and we can help from there...

As fore mileage... 15.6 really isn't that bad. There are people that get higher, but there are people that get lower too. Thats honestly probably about average (although may be a little low for 80% highway)... You could try cleaning your MAF and see if that helps you out any on mpgs.

adamci24

iTrader: (2)

Get new coils and plug waires to go along with those plugs. Clean your MAF to be safe after that nest in the air box...Put some fuel cleaner in the next tank. And then beat the crap out of it for a good half an hour drive. That should make the car run like new after letting it sit for awhile.

The CEL code will tell us what needs to be done next. It is probably something small considering it is not affecting performance.

Hurley182BC

thanks guys for the input. i used to keep a code reader here at the house but took it to work one day, never brought it back. i just added a bottle of lucas cleaner today right before i filled up. i did take the MAF out and looked for oil on it thinking it could be from the new filter. didnt clean it though. i put plug wires on it when i changed the plugs (NGK as well) and got another 25-30 miles on that tank. its getting there...slowly. i'll let you guys know what i learn tomorrow. gonna call mazda and see about open recalls too

adamci24

iTrader: (2)

Recalls are important considering its an 04. The K&N filter is known to gunk up the MAF after awhile with oils. I would buy a stock paper filter considering the K&N offers very minimal performance increase. If you stick with the K&N it will last longer, but you will want to clean your MAF every month or so according to some people on here. The RX8 MAF is very sensitive compared to other cars, and it can dramatically affect your car if i gets too dirty. Look into the BHR ignition kit if you want to upgrade your entire ignition system at one point. If you haven't yet, get the cars oil changed at a mazda dealer and continue to do that every 2,500-3,000 miles.

2004's have had problems with engines, but since your car has low mileage, if you keep up with the care for the car, you could easily keep the car running for a long time.

I wish my car at 28k when I got it because I probably could have made the first engine last a lot longer.

DocBeech

iTrader: (1)

Bad gas mileage could be from other sources too, but your not getting bad gas mileage. See our sigs. Click on mine then go look at everyone that is registered along side me. Your averaging what many others are getting. But you can increase your tire pressure, or use a tire that gets less traction. You might also need to change out the oils in your diff and transmission. As they get older they don't flow as smooth.

TeamRX8

iTrader: (25)

I've run multiple K&N filters since 2005 and never had a problem

Throwing money at your car based on intraweb advice without proper diagnosis is a recipe for wasting your bank account away ...

DeViLbOi

iTrader: (1)

Since you had a nest in the intake...by chance did you take a look at your exhaust/cat and make sure you didn't have anything in there? One of the winter advices has been to put something in the exhaust tips to keep animals out. Also you might want to check the vfad tube for nesting debris, you will have to remove the front bumper for that. A seafoam probably won't help much, but can't hurt and is fun as hell. Finally...as said above...beat the snot out of the car.

Hurley182BC

well played devilboi! after throwing the scanner to it, it came back with...P0420-Catalytic converter efficiency below threshold. yay to the ******* who never drove it! and for running it without all the plug wires hooked up. as you all know, all cars sold here have an 8yr/80,000mi warrenty on all emissions parts(if you didnt, now you do). so yeah basically the cat is plugged up and judging by the fuel trim data, its that and not O2 sensors. the local mazda dealer is fixing it next friday so we'll see how it goes from there. she even said "with the new PCM update that im sure you dont have, you should expect at least 20mpg average. less than 280mi on a tank is unacceptable to us." yeah i dont exactly believe that, but this should help alot with fuel economy issues for me, and anyone interested in getting theirs checked, in the future.

thanks to all feedback provided!

DeViLbOi

iTrader: (1)

Get that **** in writing and hold them to it.

alz0rz

iTrader: (41)

Yeah.. lmao.. that is NOT the way it works.

Detrich

after the so-called "flash" mazda did in 2006, my MPG went from 21/22 down to ****... used to actually get close to just under 300 miles per tank until then. but, what can we do? we knew this car had engine failure issues, and mazda was scrambling to improve reliability. i just wish mazda had been more transparent about what the flash was doing...

also, make sure you are using quality gas. if you continue to see CEL's try a different station/ brand.

04Green

iTrader: (1)

If you have not, I recommend an ECU reset, either battery disconnect or 20 brake pedal push approach. If it learned to live with bad plugs, broken wires, and bad coils, it may be having a hard time unlearning...

Also, check the links in my sig, they will help, the $100 is based on my education with my 04 Gt...

and, welcome...

Hurley182BC

Its been about a week, so I'll update everyone on what happened since the dealer warrenty cat was installed:

How does 318miles on a single tank sound? For those of you who have shitty mileage and thought a "test pipe" would be a great idea...fail. agency power makes a high flow cat for us(as im almost positive everyone on here knows) so thanks to everyone who threw in their 2 cents. it was all helpful info!

DeViLbOi

iTrader: (1)

ermm...no...Agency Power makes a test pipe/midpipe...there is no cat in their catalog for the RX8.

04Green

iTrader: (1)

318 on a tank is really good.

It took me a lot to get to actually see the 3. I can occasionally get there without the light on now, but means highway driving at about 68 to 70.

Hurley182BC

ok my bad it wasn't agency power...rx-7store. still, no reason to have a test pipe on a street car. that's all I'm saying

lordagrabah

iTrader: (1)

Yeah rx8's are not for the impatient. 318 is phenomenal. I've probably gotten 235 tops before the light came on and have no idea how much further it can go once the light hits.

xexok

On long highway drives I get about 21/22 mpg easy, so if your doing 80% highway I would expect somewhere around that area. This car is actually not that bad on gas for road trips I was pretty surprised when I drove to Colorado and got that mileage.

Slickaxer

So i am in a similar position with Hurley, got a new 04, 6 speed, 37k miles. And it gets 15 mpg. The thing with my car, is it was driven by a woman in a college town, so i really really doubt she did a redline a day... So i am scared that my Cat is not in the best condition. However, my check engine light is NOT on, and I am fastly approaching the 8 year mark for mazdas warranty on emmision parts. What do you guys think?

DeViLbOi

iTrader: (1)

@Slickaxer

1) Seafoam Seafoam Seafoam
2) Clean MAF
3) What is the age of your coils/plugs/wires?
4) What are your driving habbits? 15mpg might be normal for you.

Your car doesn't have the miles on it for me to be worried about a failing cat in all honesty. You can visually inspect it but I will assume that everything is going to look fine.

Another thing that you might try, and that I have been considering, is an oil additive called Marvel Mystery Oil. If you search for it here you will find a thread from way waay waaay back when, when someone used it and their engine failed. In the thread he said it was determined that the Marvel Mystery Oil that he was using as a fuel additive was actually removing so much carbon from his engine that the engine wasn't actually getting the protection it needed. I have been considering using a couple ounces in my car on a single tank of gas before I seafoam just as a way to help get as much carbon out as possible. There is a risk involved that I am still weighing through, but I think as a one time shot it wouldn't hurt too much.