Rough Idle. Completely confused.
 

Hey guys.

I would've posted this in a sub forum but I wanted this thread to get more visibility in the general area where people spend most of their time here.

I'm having an interesting rough idle issue.

I spent a good chunk of time and cash trying to repair the issue myself.

I in the past 3 weeks have installed brand new spark plugs (OEM), and wires (also OEM).

Idle was still rough.

So last week I ordered 4 new coils from OnlineMazdaParts.com which I installed tonight.

Everything went on nice and tight.

I reset the computer then fired the engine up.

I noticed barely any improvement in idle quality. The tach needle stays pretty still around 900, or 800 and doesn't fluctuate rapidly or inconsistently.

The old wires were arching. The old plugs were fouled up pretty badly and covered in a grimy / acidic orange fluid. The coils had severe discoloration on the bottom of them.

So I was pretty confident that all of these new parts would have resolved the issue.

I do notice a difference when going through the gears, but as soon as I let her down to idle I get the nasty sputtering.

I let the engine run in the driveway so I could listen to the exhaust. It's constantly popping. Little crackle backfires.

I will be checking my engine mounts tomorrow to see what kind of shape those are in, but if they are intact I'm at a complete loss.

You know, if the engine was just rough and there was vibration I could safely assume or hope that its the mounts, but the spitting of unburnt fuel constantly and the popping which coincidentally falls insynch with the engines somewhat violent stuttering tells me I may be looking in the wrong direction.

I know that was a big post, but I would truly appreciate some feedback from the more experienced owners on the board.

Thanks for reading.

well to tell you the truth my 8 seems to idle rough around 800 but if it's idling about 1000 or so it stops is that the problem? if you give it a little gas does it still do it or does it stop. If it stops its just your engine almost stalling out like when you almost stall on a hill because you let out the clutch too fast but my exhaust doesn't pop when idling I'd def. try the motor mounts then get back to us with your info! good luck though

Like I said, once I get on the gas and bring the car to about 1000 the engine gets completely smooth and runs and sounds great.

Idling (as in, no pressure applied to the gas pedal) = shitty idle. The shifter itself vibrates a little bit, but the popping of exhaust bothers me.

Also if I listen around the engine compartment when the engine is running it sounds like it's gasping for air. Like a quick sucking sound for every rotation of the rotary. It's coming from somewhere near the firewall though, towards the center of the bay. Not near the intake.

I'm so stumped but some weirdness in me kind of likes troubleshooting stuff like this.

Find a good rotary/Mazda mechanic.

You have a stock intake?
Filter okay?
Bad MAF?
Did you knock off a vacuum line?
Someone with more experience chime in............could it take the computer several cycles(starts and driving) before it re-learns after all the installs.....esp. the coils?

Stock intake. It's clean. I had to take this out today to get at the coils more easily so while it was out I checked it out. It looks good.

The MAF is visually intact. No grime, build up, craps or damage to the actual sensor itself.

It's been doing the sucking sound for a while now so if I knocked off a vacuum line it was a while ago. I do my own oil changes and have replaced the air filter numerous times. So I work pretty specifically around those areas, are their any vacuum hoses around those spots that I should check? And if so, how do I check?

My 8 tends to idle rough as well. Always has, which can be a little annoying. I have taken it into the service shop a bunch of times, and it seems to be normal (hasn't affected anything else).

Has your 8 always idled rough? Or did it just start?

It started getting really bad about 3 months ago.


Now here's the real question because I always hear around here, "rough idle is normal on this car."

Is it normal that the 8 idles rough right out of the factory.

OR

Is it normal that the 8 begins to start idling rough at or around 40k miles.

Compression check?
Motor mount? (I know that seems weird, but there is an interaction between the sagging of the right mount and the knock sensor.)

I don't know how to check compression, but I'm going to go do a search on it right now.

There is a slight knocking now that I think about it. It's faint, but it's there.

no lack of power in any areas correct?? if so i'd say your cat is starting to go.

I doubt it's any vacuum line. I was just throwing out some ideas. See MazdaManiacs concerning the motor mounts and knocj sensor. That seems like it might fit the bill. At 40k that's plausible. Also.............it could be the cat since you hear some other noises.

Yeah I seriously think you're fine like I said it just doing what it does when you don't give it enough gas and let out the clutch starts to vibrate and almost shut off it's like the idle needs turned up like on the old carb cars whent he screw would vibrate out and make the idle RPM go down I say you're just fine. I dont' think the popping is anything to be worried about but as someone said about the cat it prob wouldn't be a bad idea to have someone look at it just to make sure. If nothing is wrong with the cat I say you're 8 is just fine!

Should not have rough idle. Both rotors should run smoothly together - it sounds a little like once you get up to speed, heat and compression are taking over the firing and timing so it runs smoother - so the timing may be off -you may not have the fuel set right, there could be a clog in an injector, one rotor could have carbon build up, the air-fuel ratio is bad (the high carbon build up suggests this), too much oil is being released into one rotor .... But you should not have a mess on your plugs and you should not have rough idle!

Pester Far Side and Rotory God for their input - Swoop also pretty good...

Can you feel it / hear it inside the car?

I was concerned at first when I stood behind my car for the first time while it was idling and noticed it went like "mrmrmrmrmrmmrmrBopmrmrmrmrmrmrmrmrmrmrPop"... I thought "something must be wrong with the idle". But the car run just fine, consumes gas/oil as expected, pulls as expected... went thru a few complete check-up with the dealer and no problem, all is fine. Can't hear it from inside without actively trying to. I also have a bit of vibration in the shifter but every MT car I drove has some.

There might be something up with your car, but I, as a complete paranoiac about the condition of my car (somehow I'm always searching for hints of something meaning big trouble) I can tell you that sometimes it's better for your overall "enjoyment of the car" to just ignore it until there's a real and concrete sign of something wrong (eg: powerloss, CEL, etc).

Yes being cautious and proactive about it can save you money down the line, but if you worry about every little thing you might end up worrying for nothing.

Please show us the old spark plugs.

Several things.

Since your car was running with bad ignition for a while, try some injector cleaner and get it up on a nice long highway run to see if you can clean some possible carbon from the ports.

I had a back fire thing for a while that turned out to be a cracked vacuum hose port on the intake manifold right in front of the oil filter. Needed a new intake manifold to fix that, but it cleaned it right up. It took six months of bad idling before that set a check engine light.

Have you hooked up a scanalyzer? Sometimes there can be stored information without a check engine light being set.

All things clean and running well, the car should not idle rough. My car has gone in and out of rough idle in the 53K miles that I have had it, and rough idle is an indication that something is a little out of whack. Best of luck tracing it down.

My 2 cents......
 

I had an awful idle for quite a while, which turned out to be the vacuum hose for the v-fad.

It's right below the throttle body, and could be heard sucking when I got near.

The solution was that the dealer hooked it up to the reader which showed a "long-term-fuel-trim" of 30% - way out of spec, it was idling really lean because of the un-measured air leak.

The only other thing I could suggest is to clean the MAF (not just the temperature sensor - see the DIY Clean the ACTUAL m.a.f.

S

v-fad............that's what I couldn't think of before.......brain fart! This matches the location of the sucking sound that was reported to be near the front center of the engine bay but away from the intake! More to the left, ya know?

I just took mine out and put a plastic tab on the nipple.

No idle issues whatsoever. the VFAD vacuum is useless anyway.

Those nipples are cheap, 2 bucks can get u 4 at pepboys.

According to my dealer "Your engine is supposed to shake a bit there buddy.". This was after I had the motor mounts replaced and still felt a odd shudder every so often while at a stop light.

Check the motor mounts if you feel as if the engine is vibrating like a V-8. Mine was and now its alright, but not fine I still get the odd shudder which is annoying.

going with motor mounts, and reset your ac amp... it does make a difference..

you dont mention the year, or mileage.. but at 50k miles mine were done.. they have changed the mount also.



beers :beer:

I just (finally - literally 6 hours ago) put a new mount on my right side and OMFG.
I really had just accepted a lopey shifter in this car - especially since the new (and, apparently special) motor did it too.
However, Karl (the QMD dealer tech and club buddy that helped me with the install), pointed out that the mount was sitting too low (sagged) and said that 99.99% of the rough idle issues are solved with the motor mount.
I just kinda shrugged it off, but I figured I had to get fresh plugs so I'll grab the mount while I'm out.

Night and day. The shifter is absolutely still at idle.

The interaction is with the knock sensor. The mount sags, it makes contact, the knock sensor feels it, retards timing, the motor shakes, it rubs harder, the knock sensor pulls more timing. Et cetera.
I have actually seen the interaction with the timing on my logs, but didn't put two and two together until now. I should have, since on my original turbo system, the wastegate canister would occasionally touch the frame and the exact same interaction would occur.

yep,

aint it cool, and depending on how you pulled the motor you ppf might be off. might check it..

beers :beer:

Nah. I've had the PPF out enough times that aligning it (cross-member bolt method) is second nature to me.

The sputtering issues and shifter vibration make sense now if it is going to be the mounts, and the mounts correlation to the engine timing.

I'll check into this tonight.

I'm also going to clean the MAF with the above replied DIY.

Are the mounts something I can replace on my own with standard garage tools?



Guys thanks for the help. I think we may be isolating the issue here.


ps: replacement of the spark plugs, spark plug wires and coils has definitely done tremendous things for this cars performance. it ripped on the highway this morning like it used to when I first got it. I recommend that if you've gotten "meh" used to your engine being a little too tame or not as potent as it used to be lately that you replace most of the ignition components and then FEEL THE DIFFERENCE.

+1 on the maf cleaning -> i'm about to do mine

& I never would've thought to connect the mount issues to timing either! (woo -> learned something new!)

gonna keep this sagging right mount in mind as I rack up the miles.

Yes. It just takes a floor jack and 14mm box wrenches and sockets.
The trick is to get the car on jack stands, loosen all of the mount bolts and then raise the engine with the floor jack to unload the mount. It is best to put a piece of wood on the pad of the jack to keep from duffing the oil pan as you lift the motor.
The whole operation takes me about 20 minutes.
Figure about 2 hours for the uninitiated.

A DIY for this would be swell.

I'll check the mounts tonight.

Where can I get replacement mounts?

Rosenthal didn't have them as far as I could tell by browsing the site.

There are a pair for sale somewhere on this forum.
www.onlinemazdaparts.com has them, too.

Update:

Spark Plugs replaced
Spark Plug Wires replaced
Coils replaced
Air filter cleaned
Oil / filter changed
Mass Air Flow Sensor - Cleaned


I picked up some CRC brand MAF cleaner yesterday and cleaned the MAF.

Still no good. Rough idle.

I've only driven it to work, so maybe it will take a few more trips to reprogram itself?

My last resort / hope is that it's a motor mount.

Let us know........some are watching to see what becomes of all this.

if you are on the last flash it does take a while for the ecu to relearn, but motor mount are going to be it..

beers :beer:

Welp.

I have an update.

And a significant one at that.

After all my personal troubleshooting I could not get the issue resolved on my own.

So I brought my 8 to Liberty Mazda in Hartford Connecticut yesterday. I was there a week ago to get a tailight replaced for condensation, but I didn't tell them about the idling issue because I wanted to spend more time on it on my own.

I was so impressed with their friendliness and customer service with the tailight issue that I decided to bring it in yesterday for the idling issue.

They did a quick listen and told me the idling issue was definitely something major. So I went home without really knowing what it was because they were closing at the time I was there and that was all they could tell me.

So I got a call today from the Service Manager there who told me that they called Mazda and Mazda told them to replace the engine.

There was a compression issue with one of the rotaries, and it was apparently beyond repair.

So after all that troubleshooting it was something that couldn't be repaired with any of the following:

Replacing spark plugs
Replacing spark plug wires
Replacing coils
Cleaning the MAF with specific MAF cleaner

The engine is being shipped in from where ever.


So I don't really know what it is, or was but I'm kind of surprised it turned out to be this big of an issue.

I'm glad I'm getting a new engine in the long run.

Just wanted to get that bit of info out there.

If your still under warranty and you have the knocking rough idling issue and you've tried a few things to get it running right again, use my story to guide you in the right direction.

I'll let you know how the new engine goes once its in.

Thanks for all your help gents.

btw...


2004 MT
48k miles
Oil changes every 3k miles.
Air filters replaced on a regular basis.
Daily driver.

Don't know what I could have done, if anything, to prevent this.

Oh well. New engine :lol2:

This has me very concerned now. I just got my car and less than a month ago I test drove a few 8’s before I decided on my current one. They all had rough idle except 1. My car does have a rough idle and backfires “quiet popping”. It really didn’t bother me at all just figured it was semi normal and except it. Did you notice any power lose? I’m really hoping they replaced your engine because of the low compression and not because of the rough idle. Hoping mine can be fixed with a motor mount.

What type of driving did it get, hwy, city, agressive, gas reg-prem, ping(MIAC), TSB's all done. Anything you can think of.

The rough idle was a result of the compression issue.

You should be concerned. You need to bring your car to Mazda asap to have them check it out.

While there are most DEFINITELY different types of rough idle, mine was pretty violent. If you think yours is bad, and you shouldn't have to think too hard about it, bring it in. If you don't get a good answer from one Mazda location, go to another.

I went to 3 different places before I finally found one who actually cared about my car.

• I do a balance of both. My house is a good 15 miles from the highway, so my morning commute consists of about 20 minutes of city driving, or country road driving if you will, then 10 minutes on the highway.
  
• I drive to the beach often which is also about an hour on the highway.
  
• All around the balance between city and highway driving is about even.
  
• I do drive it aggresively quite often. Nothing completely asshole-like, or extreme, but I get on the gas and definitely put it through its paces about 2-3 times a week.
  
• For gas I've been using 87 since I got the car since after reading on the boards here that people who were using above 90 were getting some pinging and ticking.
  
• I've used different types of oil. Nothing above 5w-20 though.

The car was never right from the beginning. *edit* By saying the car was never right I don't mean that I bought it knowing it had a shitty idle. I bought it at the time not knowing that an idle like that was completely abnormal for an 8. After hearing from numerous rotary techs that an 8's engine should idle silky smooth I then knew that "all this time" the car was never right from the beginning. I just want to make sure no one thinks I bought the car with an engine issue, then neglected it, and continued to beat on the engine*edit* I bought it used with 33 thousand miles on it. The engine has gotten progressively worse from day one.

My fear is that we may never end up knowing why my car went down this route without being able to speak to the previous owner.

Mine is an 06 and has always had a bit of a rough idle. at 1k its fine at 800-900 it sounds like it's laboring a bit. I was thinking of just asking to have the idle bumped to 1k next time I'm at the dealer.

Mine was fine at 1k too.

Sometimes it was drop to 500 at a light and the car would shake like a bitch.

I wonder how long I drove the car with a huge lack of power.

More than that I wonder how long I thought my car was running at full power, but really wasn't. I wonder what the engine should REALLY feel like in terms of power.

I reckon you gonna find out!

I just hope the new engine fixes the issue.

I've heard of alot of guys having worse luck with the rebuilt engine.

[QUOTE=swoope;1883643]going with motor mounts, and reset your ac amp... it does make a difference..

you dont mention the year, or mileage.. but at 50k miles mine were done.. they have changed the mount also.


How do you reset the AC amp? This can help idle? Interesting.


Should a (decent) dealer be willing to do a compression check under warranty if you have rough idle or possible power loss? Sometimes after my 8 has been idling for a min. or two when completely warmed up, it will hesitate or need more throttle to get going in a 1st gear take off...Any ideas? I have done the TSB test for bad motor mount and it seems like I need to get a new mount b/c it fails the test.

https://www.rx8club.com/showpost.php...54&postcount=8

the link for the ac ?

the other two are yes.. if you found the tsb for the mm tsb the last recall notice should be simple..

good luck it is sooooo much nicer when smooth..

beers :beer:

^Hey according to my local service rep the car is supposed to vibrate like that.............. :uhh:

After I start my new job I'm going to Synaptic 3 in NH and having them do a compression test on my baby and then compare it to the papers I have stored somewhere (I hope I still have 'em). I have a A/T and well yeah sucks to be at a stop light and then have this quick violent shudder run through your entire body. I got the motor mounts replaced awhile back and it made it softer thats it. Hearing this story is getting me somewhat concerned but at the same time relieved since I may not be pariniod.

Mine nver drops below 800, so I'm sure it's normal, just seems to run so much smoother with another 100-200 RPM.

[QUOTE=Rhythmic;1905692]
I may be misunderstanding you but they did a compression test for you, found it was bad, and did nothing to try to remedy your issue?

Or did you mean you did the TSB check on your own?


I brought mine to 3 dealers in Connecticut before one was willing to help me. I called Liberty Mazda in Hartford CT, they had me bring my 8 in the next day. They did a test, told me compression was bad and told me the car needed a new motor. No hassle, no waiting, no bs.

A good Mazda Dealer should be willing to help you. If Mazda neglects there RX8 customers they know they could be losing future Mazda sales in general. This is my 3rd Mazda. MX6, M3, and the RX8.

If I continue to receive amazing service from Liberty Mazda, who I only recently discovered (unfortunately) I will definitely consider jumping into my 4th Mazda when the time comes. (or the next rendition of the Rotary comes out)



No updates on the new engine yet. I assume it is shipping in from overseas?

Its good to know that you have a good dealership around you.

I've already been to 3 dealerships(NYC) and they're just a bunch of dicks.

Im gonna try my 4th one soon .... I have some TSB for them to do. wish me luck ...