Raptor75

I have been noticing that my RX has been sluggish lately below 4K RPM. Once I hit around 4K power seems to pick back up. Any ideas what this might be?

RX8Soldier

iTrader: (24)

how many miles on your engine/ plugs/ coils?
Any mods?
Checked your cat?

Speed_8

I thought thats normal

hokie027

Yeah. It could be that your SSV is stuck open, but if that were the case you would have an irregular idle which you do not seem to be complaining about... Generally this will throw a CEL light, but in rare cases it may not... you need to provide more information for us to be able to help you.

How do you drive your car?... and what RX8Soldier said...

Answer those then someone will be able to assist.

Raptor75

Car is an 05 bought in early 06, about 35K. Driven mostly city with about 30% HW over the last year, before that about 95% city . I don't think it is the cat because power is normal at higher RPMs which is where a clogged CAT would show the most reduction. I would think the same would be true for Plugs and coils. Engine compression would be my guess but I'd like to see what other would think. Modes are few, larger rubber 245, CAT back exhaust and K&N filter.

From time to time I have noticed a lose of power at highway speed but it is sporadic and infrequent. I'm thinking seals may start to be sticking. Planning a sea-foam treatment in the spring and looking into a water injection system to clean the carbon out on a permanent bases.

Georgia8er

If you're at 35k, you are probably close to needing new plugs anyway. It would be worth at least pulling them and having a look.

Raptor75

They were replaced at 5K so they really only have about 30K on them. Of course there is no harm in looking them over, you never know.

xexok

Thats what I was thinking lol.

If your plugs have 30k on them then its time, I think most people replace them every 25k to 35k miles. I think once you take your plugs out and look at them you will see why. If you have the money you might also consider the coils and wires, and if you have more money than that get the BHR coils instead and never have to change those again.

Speed_8

you said you run a k&n filter, from what I hear those can oil up your intake... clean your maf, it could be that when at lower rpm, the sensor is just not reading the flow properly.

hokie027

Well if he had a dirty MAF it would be immediately obvious when slowing down out of gear, and also when sitting idle at stop lights... much the same symptoms as a stuck open SSV. The fuel/air ratio would be all off causing the engine to have an irregular rattle. When it happens at higher RPMs... I would find it extremely unlikely that it is a dirty MAF.

Also, is the K&N a drop in or is the short ram intake? I've had the short ram on my car for a short while and it DID cause the car to pull irregularly in higher RPMs when it was hotter--due to engine heat etc.

My money would be on plugs or coils... I know that seems to be the ketchup/mustard answer for this car, but 50% of the time it seems to be the solution to the problem. Do you know how to check each coil for good spark?

Raptor75

I cleaned the MAF last summer and idle is fine. Also I have driven the car for the last six years and can tell when something is different. Spark plugs are worth looking at, coils make no sense. If it was the coil it would be more evident at higher RPM.

Tiler02

I am having the same problem. I think it is a fouled plug. I took off the other day. I floored it and the car sputtered before going. It has been doing this ever since. I am guessing a week coil cause the plug to not fire and it fouled the plug. That is just a guess.

OverLOAD

My 2004 RX-8 seems to have a similar issue. I had several issues which I had looked at all together, and also had low compression which just got me a replacement short block at 56k miles under warranty still (kudos Mazda).

I would be willing to place bets on either a cracked/leaking intake manifold, or bad coils. The RX-8 has 2 sparks per rotor, and based on the RPM and throttle position, the timing changes wildly over about 40 degrees. Hence a single bad coil on one rotor could cause rough running and vibration within a narrow RPM range under load.

I agree with the general comments about the MAF not being a likely culprit, since a decent idle, and a decent top end seem to rule that out. I also got new spark plugs less then 100 miles ago, and I experienced this problem both before and after the plugs were swapped.

My coils were diagnosed OK by the tech when I got my plugs swapped, but I did have only two of them replaced a few years earlier. I've heard many stories about coil problems, so I would start there.

Cheers,

OverLOAD

Raptor75

The car is getting worse, below 4K power is getting weaker and I'm seeing lack of power at highway speed. I'm starting with the plugs which I just picked up. Next up will be coils but I don't think it is a coil issue, car is not breaking up in the higher RPM range. I did throw a CELL the other day that showed miss fire in the 2nd rotor, cleared it and it has not come back.

I think if the plugs don't clear this up it my be a clogged CAT or failing engine. I've checked the CAT and it is not glowing so I'm not sure if this is the real issue. It appears that failing engine could be the cause but we will see. One more thing the car is hard starting when cold and hot, about equally hard. Hope to have time to put the plugs in this weekend or next week.

xexok

I know hard starts when hot can be signs of needing a new engine but you dont really hear about hard starting when cold for that. Hopefully the plugs fix it for you.

kartweb

Very likely coils. Its not like a piston engine, keep in mind there are two plugs per rotor. I think that tends to mask or prevent the high RPM miss.

Look at the bottom side of each of the coils after you pull them. There is a black potting compound; when they short there is a white discoloration that forms.

It seems to be worse at low-mid RPM. As they get worse it will throw a CEL at high RPM.

Engine turns over a few more times to start. Slight miss at idle. All signs of coils.

Georgia8er

I'm thinking something in the ignition system, for sure. Could be plugs, coils, or plug wires. Might be as simple as a plug wire not fully seated.

Raptor75

Thanks, if you don't mind me asking have you had real world experience with this issue or is this info you have read?

DeViLbOi

iTrader: (1)

It has been proven over and over again that the white discoloration is a myth and can occur even with brand new coils.

Raptor - By chance have you tested the intake system as described in a DIY that is around here somewhere? Because of things clearing up at higher RPMs to me it sounds air related...whether it is a failing component or a vaccuum leak. Also have you done anything to your car prior to these symptoms appearing? Catch can? Air Filter install? etc?

Raptor75

Nothing new on the car. Power does appear to be down across the board but is most noticeable off the line up to about 4K and just a general lack of power at highway speed.

I have not looked at the DIY but will do so, after I switch the plugs. For the record I have 36K miles on the car, 5 speed manual and has spent 90% of those miles in city driving.

Raptor75

...and we have a winner! Bad Coil!

I was plan to switch plugs this weekend and see if that corrected the problem. On the way home power dropped off radically and the car was running like ****. I knew one rotor was not firing and had a constant flashing engine light. I figured I'd try to limp the car home but after a couple of miles I start to smell smoke so I pulled it over and looked at the CAT, it was glowing. Since the ignition system was not lighting the fuel it was duping straight into the exhaust and burning in the CAT.

Towed it home replaced plugs first which were not so bad ...on to the coils. Took them off and only a small white coloring on two of them barely noticeable but, they were bad. After replacing them the car fired right up and has been running great ever since.

I'd like to thank Mazda for sourcing such crappy coils in the first place. I haven't had a coil fail on a car since my 72 Fiat spider.

So in summery,

- Car was getting hard to start hot or cold.
- Lose of power especially off the line at low RPMs and Highway speed.
- Chirping sound at start-up (Caught this in hind sight, I thought it was the engine at first)
- Rough ideal as it grew closer to failure.

Fix:
- Picked up coils at NAPA for $40 each, they looked identical to OEM.
- Replacement took about an hour, easy to do if not a little tight to work on, I did not remove the rubber intake pipe from the filter box to the intake manifold. This made it a little harder to reach but doable. One bolt and two plugs per rotor. The three wire plug needs to be pushed at its base (closest to the wires) to release.

One more thing, when I went to change the spark plug I noticed that the protective wheel well cover and its two securing screws were not there. The only people to every replace plugs was Mazda's dealer, so it looks like one of their shaved chimps didn't bother to put it back. Again thanks Mazda another job well done!

OverLOAD

I just finally got my replacement coils from the UPS wagon today. Upon inspection, the tech has installed two of my earlier replacement coils (100B series) in the middle positions of the four coils, while the front and rear coils were still factory original cica 2003 100 series coils.

I swapped all coils 20 minutes ago (took about 45 minutes total), and took it for a test drive. To my satisfaction, ALL of my rough running problems are totally gone. The car now finally runs like it should.

I think that my particular issue was just a single bad coil for one rotor with the advanced timing. The engine normally seems to operate with a significant amount of retart in the timing (according to my in-car Scan-guage-2 diagnostic).

Very happy now

PS: I spent $170 on 4 new coils, vs the (st)ealership quote of $700... ouch.

Raptor: Glad your problem is fixed too. My problem went on for more then 2 months, so became VERY frustrating.

jonspurs

Thanks for the update Raptor.

I've been getting chirping noises with slightly longer start up times.
Accelerating in-gear between 1500-2500rpm it's not smooth.
Exhaust note sounds a bit deeper - did this happen to you?

Pressing the gas in neutral the engine revs fine.
I've changed plugs and leads, and with this, the chirp only happens sometimes with quicker start up.

Soon will do coils.

Jon

jonspurs

UPDATE:
Coils replaced and now car is running perfect :-D
It was these damn things all along! Plugs and leads were changed first, didn't notice much of a difference, but with the new coils, the hesitation / jerkiness / jerky / kangaroo / struggle at low revs has gone, and throughout the rev range the car pulls hard again as it used to. Exhaust note sounds back to normal too.

I decided to go for the BluePrint coils from Camskill (£50 each) as they come with a 3 year guarantee and have heard the Mazda OEM coils are 12 months guarantee need replacing every 30k anyway:
http://www.camskill.co.uk/m46b1133s3900 ... ards/RS_GB

Which is the same as:
http://www.camskill.co.uk/m30b0s2916p62 ... _ADM51488_

Also I saw Dave's post mentioning BluePrint leads were in better condition than the Mazda ones, so would hope this carries through to other parts they make...time will tell.

Looking to get Caraclean to clear out - cheers for the tip.

I'll post macro photos of the white-marked old coils tomorrow.

Jon

jonspurs

Today the coils look ok (cooled down? moisture?) compared to yesterday - the black area was actually white. There's a bit of glare/relection from outdoor light.