RX8SaxMan

So earlier this year my RX-8 starting running rough with a raspy sound after it was nice and warm. On couple of occasions I got the misfire CEL. I figured I'll replace the coils, so I bought 4 new ones and stuck them in.

The car definitely felt better afterwards, but after long (1.5 hr+) drives, the raspy sound still comes back, and I've had the misfire light once more. Just for fun I took it to the dealer to get their opinion, and they're telling me my trailing coils are bad. They're only 5 months old, and the problem only happens after long drives. Could the dealer be right, or does anyone have a suggestion of what else it could be?

My car has about 80,000 miles. I just bought a new fuel pump, but haven't had a chance to install it yet. Any chance it will fix the problem? Thanks!

invasion08

iTrader: (7)

It could be the trailing spark plugs because if the coils were not working up to par your plugs could go bad fast. Take the trailing plugs out and see what they look like. If you need new plugs go to www.autopartswarehouse.com you can get all 4 shipped for 85 dollars.

swoope

iTrader: (5)

fuel pump. i have been through this before.. btw, have you been premixing?

beers

RX8SaxMan

Cool. Hopefully I'll be able to find time this weekend to swap the pump. I have never premixed.

elysium19

iTrader: (1)

I know there was at least chatter (substantiated or not) about premixing and the fuel filter. I don't really know where that's located......if you buy a new pump, is the filter new as well, part of that unit?

RX8SaxMan

Yes, the pump and filter are a combined unit.

swoope

iTrader: (5)

what flash are you on? it could also be drying apex seals depending on the flash..

beers

RX8SaxMan

I just had the MSP16 recall/flash done a couple months ago. That was the first thing I tried since it was free. It helped my low power problem when the outside temps were 100+, but the raspy sound was still there on long drives.

swoope

iTrader: (5)

ok,,

at least this is interesting.. i am going to make some guesses..

04 auto? you got it used? and this is the first flash it has?

beers

RX8SaxMan

'05 6MT, bought it brand new, and always kept up with the flashes :-P

swoope

iTrader: (5)

ok,

this is fun..

raspy and in starts to sound more deep? the 1.5 hour mark is my clue.. that is when my fuel pump would get warm and shut down.. but after 5 min it would start right up and drive fine..

how old are the plugs and wires? do you have some friends you can swap stuff out with?

beers

RX8SaxMan

Yeah that sounds exactly like what is happening. After the engine has cooled off it drives great. I changed the wires with the coils (5 months ago), and the plugs are about a year old. Unfortunately my only friend with an RX-8 lives 2 states away, so swapping parts isn't gonna happen. I'm hoping replacing the fuel pump will take care of it...

swoope

iTrader: (5)

before you replace the fuel pump send me a pm.. i would like you to try something..

beers

Faxie

This sounds a bit familiar... i just ordered new coils.... same kind of sound (i think)

Could it be that the fuel filter needs replacement?

RX8SaxMan

From what I've gathered, the raspy sound is the result of poor ignition. This can be caused by bad spark plugs, wires, coils, fuel pump, or possibly low compression (i.e. new engine time).

So far I've done everything except replace the fuel pump and check my compression. It only happens to me when the engine components are hot, so either my fuel pump is overheating/wearing out, or my engine seals are losing compression due to thermal expansion.

I'll be posting here again when I figure out which one it is for my engine. For you, the coils are a good start, and you can use logical deduction from there.

swoope

iTrader: (5)

did you give my pm a shot?

beers

RX8SaxMan

Not yet. I just haven't had time (school + work is kicking my ***). I'll try to get my hands on a bottle of MMO before my next fillup in a day or two.

LionZoo

I'd be interested in this solution as well swoope.

swoope

iTrader: (5)

me

what i suggested through pm was..

8 oz of mmo into a 1ltr aquafina bottle, add gas shake..

fill tank half way, add mixture. fill rest of the tank..( this is the kinder gentler premix)

if that solves the problem it is drying apex seals, motor time.. if not the next idea is fuel pump..

my first motor had this problem.. it worked well..



beers

Potentiated

Wait, none of his posts specifically say he changed his spark plugs. I'm guessing he did but would like to hear it explicitly.

RX8SaxMan

Well the plugs I have aren't that old, so I did not replace them. I'm not saying they aren't the problem, but IMO it's unlikely. I'll probably pull them soon and inspect them, and maybe replace them again.

LionZoo

Might want to change the plugs. If your coils were bad, it could've taken the plugs with them.

RX8SaxMan

So I mixed in some Marvel Mystery Oil to my fuel per swoope's PM, and my engine is running as smooth as snot so far. I don't want to jump to conclusions, though, because my raspy sound was always most prominent in hot weather, and today it has only been about 60 degrees out. I'll keep you all posted.

Faxie

My problem isn't exactly the same though... I can't say the car is running rough, idles just fine (850 rpm, very slight vibration) but when i go WOT in 3rd and 4th gear, I get these horrible rattles (like a hard disk drive, or a coffee machine) past 7000 rpm, and a blinking CEL when i keep it up for too long.

Stupid thing is.... it doesn't always happen.

I had the problem before, and it turned out one of the plugs was f*cked, so replaced all 4 of them. Problem went away after that, but after 5000 miles or so, it started again. So my guess is one of the coils is bad....

Car has 31000 miles now btw, and it's a 2005 6mt shinka.

tunerwannab

iTrader: (1)

I want to see how this ends. Keep us posted and GL.