rough idle and misfire after a track day
 

Hi,
Yesterday I was on a track day driving my RX8 really hard. I was going like crazy on the corners, so there was a lot of pressure on my car. Constantly revving between 6-8k.

Suddenly my car engine shut off. After I stopped I could not power it on. The temperature pointer arrow at that time was in the middle, so it was not overheated.
After 10-15 minutes I tried starting my car again and it was misfiring and running very rough.

My car had 50000km (31000 miles) service a week ago. Car is all stock. Today I went to a Mazda dealer and asked them to change spark plugs.

The dealer who I don't trust very much told me even after replacing spark plugs the misfiring is still there and they have to do a compression test,

With the new spark plugs idle is much better but there is still running rough, but there is no misfire. I can't explain why but I do not trust the dealer.

I got the car back in for a compression test and they did one and showed me a print out showing graphs of low compression in front rotor bank. I couldn't tell if the print out was from my car or another car from another time. There was not time or date on it so it could be anything.

I asked him have he checked what is the cause of the CEL on. He said the error code was saying there is low compression. This sounded complete BS to me.

He said I will have to have the engine rebuilt which will cost me about $5000. I want to point out that I don't trust their word and think it is something much easier to fix while they charge me for much more.

How could the misfire have gone away with the new plugs but there is still some rough idle. Any advice? Have they done something fishy?

If you have an s2 then your car is 2009+ and should still be under the 5 year 60k miles powertrain warranty which is free replacement of the engine. Not only that but you should even still be under the 3 year/ 36k mile bumper to bumper warranty. Why would they be trying to charge you 5k while you are still under warranty?

Bought my car in october 2008. Mazda warranty here in Australia is only 3 years. :(

If the car just shut off while you were on the track it very well could be a catastrophic failure of a seal on the front rotor. Something that's cheaper than replacing the engine though is replacing the ignition coils and plug wires but if the dealer did the compression test correctly your motor might be shot. I've only seen one naturally aspirated Series 1 RX-8 around here have a massive failure (apex seal shattered) so I don't think it's very common...

Does it smoke at all?

I would check all your plugs, wires ect first. Also check all your wires from the engine harness even things like your o2. also if it has no power and a misfire check the cat...

Stephen

plugs are new, dealer said wires and coils have been checked and look good.

Will try and check the rest of your recommendations.

Thanks.

Which state are you in. I suggest taking your car to a specialist rotary mechanic for a diagnosis

Damn that really sucks. If I were you I would stop taking it to the dealer. I know Australia is pretty well known for its love of rotary so there has got to be a good amount of independent shops as skc suggested.

Mazda will be trying to give you a remanufactured engine which even at 5k you could be looking at replacing it within 20k miles again or less. Some remans last quite a long time and others do not. If you go with a independent rotary shop they could build you a quality engine out of good parts and make sure it lasts much longer than the reman.

PM Sent to OP

This morning decided to start with checking the MAF sensor when I noticed that one of the pipes to the air duct is missing:

http://farm9.staticflickr.com/8452/7...83cfc2eb_z.jpg

Not sure how it happened but it could either have fallen while driving or it was removed by the dealer. I searched but could not locate the disconnected pipe.

BTW, the MAF sensor (two wires) looks clean, the bulb has very smal residue on one side and clean on the other. So I reckon fault is not with the MAF sensor.

That is normal. Take a flashlight and look in the hole, it should be plugged like mine is. Clean the MAF though, you might as well since it is not hard.

Hi and thanks for the info..

I am pretty sure this is hole in accordion is blank, not used, (I cant check my car right now).

Now you have one of the very early S2's, not that there is any changes of concern.

So, you are still having rough idling?

I would not necessarily discount what the dealer told you, although there is NO CEL Code for "low compressions"...does not exist...misfire..yes.

I see no reason for them to tell you something that is not correct...if you have low compressions on front rotor then sadly only a rebuild/new engine will rectify.

Are you the original owner?

I would be contacting Mazda Australia and just try and see 'if' they are prepared to offer any assistance (re-new engine) IF, you are repaired to pay something to-wards it.

I would also be getting a second opinion from another Rotary Expert, or Dealer in the east.

Does not look good.

I wonder if the CEL is on wouldn't it point that there is also another issue apart from the potential loss of compression?

I want to note that after replacing the spark plugs car runs without misfiring, but there is still rough some rough idle remaining.

I mean if the issue was only broken apex seal why would I also get CEL on at the time of driving the car when it suddenly shut off by itself.

Would that be caused by loss of compression, or could there be something else causing the engine to shut down and cause the CEL to come on?

Just thinking out loud. Any suggestions are welcomed.

Found a INTAKE-AIR SYSTEM HOSE ROUTING DIAGRAM here (M A Z D A)

http://farm9.staticflickr.com/8302/7...a728b40b_o.png

The green arrows point to the missing pipe.

My car has not ever had that hose there, I went and double checked before I said it should be empty. Did you go out and check it with a flashlight yet? You should see a plug in it.

If I had to guess I would say that the 04-08 and 09-11 rx8's share that intake tube, and that hole was used on the 04-08 ones(what that shop manual would be for) and not used on the newer ones. I looked around for pictures of series 1 rx8 engine bays and there is a hose plugged into that part for them.

Check out these guys if you need a rotary mechanic. The owners in Melbourne seem to rate them highly RX8 Club Australia • View topic - RX-8 Specialties workshop relocation

No Series 1 and 2 do not share the same accordion Intake Tube, the S2's have the one less pipe and one less physical (actual) working hole.

3 (S1) to 2 (S2), although the hole and nipple platform are there the hole does not go into/through to the air pipe like S1.:)

I know it does not go through, it is just plugged. Why would they even have that part there if it wasnt the s1 part with a plugged hole? If they were going to make a whole different part wouldn't it be cleaner to just not have that piece on there?

Voe, that line pic is for the Series 1 RX-8, you have the Series II RX-8 which does not have this 'vac tube' set up, see my other post.
Much of the external stuff is not the same for your S2 as shown in that Mazda Manual you are looking at...which is ALL for Series 1.

Lets not confuse the issue about vac lines..:)

Nothing unusual for a car market to use the same "moulding" for a car part, they just don't pierce the hole as it is not required in ALL S2's in this case as it has one less vac line.

VOE...

Are you still getting a yellow CEL light on dash?

As I said before there is no CEL or DTC (symptom code) for 'Loss of compression' as there is not a fixed sensor to measure "loss of compression"...

From factory there is only one real way to measure and that is with a proper Comp Tester ( if you are coming to Adelaide I can do it for you as I have a Mazda RE factory Comp Tester.

As said before you possibly have a fractured Apex Seal or damaged Corner Seal, this is how you 'generally' get weak compressions..

Did you get a copy of the readings?, if so post them here...it could tell us a lot.

As I see it in your case we can talk until the cows come home, you need to get a second opinion from someone who can physically re-check compressions and some other parts.

What model year is your car?
Just because you bought a car in 2008 doesn't really tell us if your car is a 2008 or a 2009. There is a bit of a difference between the two cars.

BC.

BC looking at the pictures he posted it is definitely a series 2 if he took that picture. He also has another post asking if there are any plans for the cobb accessport for series 2 so he pretty definitively has a series 2.

I think this is the first series 2 I have seen with a blown engine if the dealer is right. Anyone else seen another one?

lol code for low compression complete BS.

Fwiw there was a poster around here about a year ago (Texas RX8 R3 I think was his name) who had similar problems after a track day. If I remember correctly his car kept going into limp mode but didn't actually die though. I believe it turned out to be a clogged/failed cat. I can't find his thread, it may have been deleted for some reason.

^^^ I believe his car eventually had an eccentric shaft failure from memory. I remember reading someone with an S2 with this problem, could of been Texas.....?