draiel

Ok, so first off, hi guys! New forum member here, and new RX8 owner (as of about 3 months ago)

My RX8 experience was fantastic up until about a month or so ago, when my fuel consumption suddenly increased by about 30% (was getting about 450-500km a tank, now down to about 300-350km if I'm lucky). At the same time, I had a large power drop, and now my car struggles to redline, and it takes I think about twice as long to reach 100kph as it did. Revs ok up to about 5-6k rpm, and then struggles to get to 8k from there.

So far I have cleaned the MAF, had a compression test (apparently my compression is excellent - 120 average, with a variance of 3-4), and replaced my ignition coils. Replacing the coils seemed to help a little, but not much, not sure on if it has helped with the fuel efficiency yet as I've only driven with the new coils for about 30kms.

Revved engine while it wasn't in gear and revs quickly and easily up to 9k (don't know if that matters, just thought I'd mention it).

My mechanic told me that the wires and plugs are fine, so I haven't had them replaced yet - mostly due to my financial situation at the moment.

From the reading on forums I have done, it seems that this may be a clogged cat, but I guess I want an opinion from someone who has all the facts about my particular situation before I fork out over $1000 to replace the cat. Also didn't want to do that if it was something cheap/simple that I've missed.

Most important question - if it is the cat, how long can it wait? I will have the money to get it replaced in about a month, and I only need to drive about 100kms a week in that time. Will that be ok if I don't drive it too hard?

Australian RX8, 2003, manual, 100,000km on the clock, as far as I know completely stock.

04Green

iTrader: (1)

Hello and welcome..

the cat can mess things up pretty bad. But is usually not a "suddenly" thing unless something breaks loose. Is the shifter really warm, if you look under the car after a hard drive, is the cat glowing red? Cat can contribute to poor fuel mileage. It also causes a great deal of back pressure, and that is really bad for the motor. A lot of folks do not recommend driving that way.

Another option is that the SSV is not opening like it should. This will limit top end, as the intake routes are wrong. It can also trash your mileage because there is no air where system is spraying fuel. If you can reach in and move the actuator easily though, you are likely OK. There are some pictures and a DIY that will tell you where things are. The problem is, the computer does a pretty good job of checking on things and is not telling you there is an issue. SSV stuck is the one thing you can check easy, so I would start there. I would also hit the car with a bottle of fuel system cleaner. The number of things that solves around my house is amazing.

the other thing that occurs at 5,500 RPM is the VAFD opens. However, where it is located, it is unlikely the issue since you have a big drop in power, not a gradual starvation. to test, disconnect the vacuum line. After a few runs past 5,500, it will just stick open.

If it is the cat, you can pull it, run a pipe through it to clean everything out, and put it back in. If that solved the problem, you know what it was. Problem is you cannot put the material back in. Once gutted, it is gutted. There are some aftermarket mid-pipes with cats installed that may be of use and cheaper if you need one for emissions.

Anyone else?

MountainMike68

A failed cat can kill your engine and will not always trip the CEL. Go catless, its cheaper and safer.

draiel

Ok, seems to be a bit better now (though I didn't do actually anything, aside from unplug the MAF and then plug it back in).
Haven't redlined, but got to 8k much easier, though it seemed to stumble a bit around 6500rpm. The cat doesn't glow after a 25km drive with revving to 8k at least three or four times, though I don't know if thats what you would consider a hard drive (guessing not)

JCrane82

iTrader: (3)

Are you getting any check engine lights during the power loss at high RPM? Any way to get a A/F measurement to see if you are in a rich or lean condition?

If the power loss happens at an exact RPM every time, I would look into the intake system like 04Green noted. If the power loss happens at varying RPM, it could be a fuel delivery issue. Possibly fuel pump, fuel fiter, or injectors (although less likely to be the injectors at that low of miles).

draiel

Octane Boost and Clean- Nulon Australia

Is this the sort of stuff you mean?
Probably should have mentioned I'm a bit of a car newbie...

Nope, no CEL coming on at any stage.

Also I've found that it will rev all the way to redline just fine when it is in neutral, don't know if that makes a difference...

Legot

iTrader: (1)

Replacing your ignition is the best starting point.

Too check your cat just pull it off and if it looks clogged then it is clogged (and you'll still need a new ignition). Revving in neutral wiping get you anywhere since most issues are only apparent when the engine is under load.

BigCajun

iTrader: (1)

Yes, like the others said, check the cat ASAP!
If it's clogged, you can gut it until you decide what to do.
Be sure to take the sensor out to avoid damaging it.
If the back half is intact, just gutting it will work for now.
If the back half is broken up and some pieces are gone, you'll have to remove the exhaust and try to shake out any remaining pieces.

Ricocase

In Cali?

swoope

iTrader: (5)

NO

beers

Khurram

Agree with everyone on the CAT inspection/ gutting/ replacing etc

These are the steps that helped me in the similar scenario.

You stated above that you only replaced the coils. Rule of thumb we go by on this car is that we change coils, plugs and wires all at once. Yes they are a maintenance item!

Also, while you are at it, pull out your intake box and accordion tubes. Inspect them thoroughly, if you find any oil in there clean it out. Oil may be there due to over fill and its normal. If your Air filter is soaked in oil, replace it.

Also, clean your ESS, and reset your nvram after you change your plugs wires and coils.

Let the car idle for 10 minutes or so to let it re-learn the fuel trims.

Go for a test drive, try redlining the car if the cel flashes get off the throttle.
once cell goes away, start accelerating, and redline again.

Report your findings..


It could very well be your SSV or CAT. I cleaned my ssv along with everything above and I was cat-less..

Hope this helps
All the best

MountainMike68

All I will say is there are advantages to keeping the car registered in another state.

Trex87

Ever fixed the issue?

draiel

About a month later, the car went into limp mode and I took it to the mechanic - turns out, the cat was starting to clog, and ended up clogging completely (hence the limp mode). Mechanic cleared the clog, and I've been driving it with an empty cat with no problems since.

Trex87

Thanks for replying, I had to gut my cat too but I feel as there still is blockage in the pipe or muffler because it's slow to the redline and stumbles

Rich79

It started happening after a full engine rebuild I had up graded coils and new plugs fitted a high flow exhaust lighten flywheel and new clutch car goes like a bullet bet when it gets to redline it just backfires and goes no further plz help