To all Z5 owners, please post here!

[97proLX]

1997 LX auto...
166k miles or so.....
I have problem one and two. When I first start the car it runs VERY rough for maybe 30 seconds then smooths out. through out exceleration it seems to gain then lose power very slightly. When I come to a stop the headrests on driver and passenger seats shake a little bit.
Oh, and I forgot that recently I switched to premium fuel and the hard starts went away and it runs signifigantly better but still slightly shakes like explained in this post.

[baralheia]

1997 LX 1.5L Z5 Manual here, exhibiting problem #1. Has approximately 128k miles.

MIL is illuminated, but I can not recall the exact DTC set. The code set supposedly has something to do with the downstream O2 sensor, IIRC. I'll have to swing by AutoZone and have them read out the codes again. I have not checked the compression of the cylinders.

Generally, after the engine RPMs drop down to below idle, the engine will hunt within a range of about 100 RPM of the correct idle speed. Moderate to severe detonation often occurs on heavy acceleration.

[pigeon]

As the summer progresses, I will be doing more research on this problem.

Thanks!

[rusty]

97 pro z5
125,000
Have had both issues

I did a bunch of research on the misfire issue over a year ago. Had to replace cap and rotor every 2 months due to oxidation. I found out that the cam seal behind the distributor was leaking, replace and runs fine now.
Now in my research I found that the z5 has really weak valve springs. If I am not mistaken, I bet most of you are missing on cylinder 4. That cylinder is the most known to get a burnt exhaust vavle due to the weak valve springs.
My recommendation would be find after market set of valve springs and have a valve job done. I would do the work if I were you to keep the cost down. Just take the head to the machine job for the valve job.

As far as the unstable idle, I replaced the pcv valve which helped some. Replaced all the vaccum lines which were old and due for service anyways. Still had an unstable idle especially with the a/c on. Adjusted the idle adjust screw on the tb and helped out greatly. If you over adjust this screw you will get a mil for unstable idle or similar idle code. You may have to play with the adjustment alittle to get it just right.
Also form the research I found that the idle some times has to be reset electronically once the battery has been disconnected. If you are willing to pay for reset idle this can be done at the dealer. I just assume do my own with the idle screw adjustment over a couple day period to get it just right.

End result is the car runs much better now. I have not done anything with my valve springs yet. The z5 still has very good compression and no valve noise so I will hold off for now. Once I have some of my other car projects finished then I may start on a upgrade for the head on z5.

[latinohottie]

Okay im going to ask a stupid question.....How do i know if i have a z5?
or better yet..what is a z5?

[Torped0]

The Z5 is the 1.5l. If you have a 95-98 DX/LX you have the 1.5l. If you have the ES protege, you have the BP, 1.8l.

[latinohottie]

ohh okay then i do..thanks

[RicardoS]

I read that excess exhaust does not make it out of the manifold and causes the phantom cylinder #4 misfire code po304. installed an intake, cleaned the maf sensor, egr, throttle plate, and adjusted what I call the idle screw. I have also read that if you opperate your mazda at high rpm's before it has reached complete opperating temperature, which takes longer than when the needle says so it may cause this misfire code as well. I have not had the cel come back on but once in the last week It was after a cold start and fairly rough idle. My z5 only idles rough at start but after i let it warm up a little and get it up to opperating temp coming off an exit only the passanger seat shakes "slightly" I would still like to continue troubleshooting the idle if anyone has any comment thank you


Free Images

[speedyking000]

my car idles at 500 rpm....is that normal. i had a misfiring cylinder i think it was number 2. the guy just told me i needed a new spark plug and new wires...i did that and bam it fixed it...payin 1k for a shop to fix it sounds like a rip of man

[RicardoS]

750 in gear and 800rpms in neutral or park. yes the plugs, wires, distributor, cap, and or rotor cap are the usual culprets of the misfire code, the fact that it is only one cylinder means it was either that #2 spark plug wire (or plug itself) and connection inside the distributor cap (specifically the #2 connection). But I replaced all of those and still got the misfire code until I did everything else. Case to case I think, but the exhaust build up theroy is a good one as it gets "trapped" in the exhaust manifold it gets back into the cylinder and makes the ecu think their is misfire when their is not. If you do a compression test and the number 2 is way out of spec, you probably have some other serious issues. I also thought injector so replaced the number 4 cylinder injector and no difference. Not until I cleaned the egr valve and installed the shortram intake did I achieve from any po304 code to appear!!!!! It doesn't sound like you have as an extensive problem as I did but hope this may help you if you have any further issues

Free Images

Free Images

[RyanV]

I've had #1 issue with all of my Mazdas

I've had the years below

Protege
94'
98'
00'
02'

Mazda 6
05'

all of these car's have had the idle that sometime's dips down and get's a little rough. It's probably a Throttle postion sensor or Idle speed controller not getting correct voltage for a split second. Could be way off though.

[strutman]

if your car idles weird it could be the magnetic sensor that reads off your pully...i forget the name of it, i've replaced mine and i still run rough for the first 30 seconds when i start it... the name of it escapes me right now, but i believe it's an ecu problem I'm having since i replaced the sensor and it still throws the code, either that or wiring.

[stamar]

oh wow

I have problem #1

I have a 95 lx with 128k miles on it

I just bought it
I was going through basic tune up one step at a time to see if i could eliminate it

I changed the oil and filter with mobil 1 and i put in new spark plugs

Its still there but i think it greatly reduced. Im going to reread this thread completely later but what is the general problem?

I was going to go pcv valve cap and rotor next. this is actually something I think is vacuum related, at least in other cars but im not sure yet

hopefully if this is a very common problem someone has something for me to straight to fix so i dont have to waste any more money diagnosing it.

the only time i dont have this rough idle is after the vehicle has been running literally for hours

with the bright dome light on, it will flicker when it goes down

with ac on the idle is actually more steady, although when it misses with the ac on the shake is more violent.

any help is much appreciated.

[stamar]

a wandering idle ok

I mean the symptoms my car has, which is whats described in #1

where the idle dips down for a second then goes back up.


Well it doesnt follow any sort of logic that valve springs can cause this.

each rotation is the same lol going on way to fast.

My dips are happening... ill listen... 8 seconds about. running fine, dip for half second, 8 seconds.

what im practically sure this is going to be is like a vacuum tube, although owners who adjusted a air sensor of some sort Im reading what you wrote. if the next round of crap doesnt get rid of this im going to look up all the vacum hoses and replace them all.

any suggestions extremely helpful

[fastmatt1986]

yeah i've got the rough idle as well. just a weird trait in the mysterious Z5 i suppose