Rough Idle, and Ive tried it all
 

Ok Im still in search of a cure for my rough idle. The rough idle occurs after the car is warm, at idle the idle will drop below 500 and then catch up but it just hunts or surges never really evens out, also if I turn the car off and turn it back on in say 5 to 10 minutes idle is very erractic. No driveability issues car runs fine under power. I have a 99 ES with close to 60k miles on it. 1.8L, 5spd, no cat, AWR header, 2.25" custom SS header back exhaust, AEM SRI, magnecor wires and extended reach plugs. What have I done to fix the rough idle? Lets see, since January, replaced the plugs and gapped them at .44, fuel injector cleaner, replaced the EGR valve, removed the throttle body and cleaned that, removed IAC valve and cleaned that, cleaned maf and made sure the SRI was nice and tight, also installed a complete ground kit. Now from doing extensive searches I have come down to these ideas, vacum leak, I dont hear anything but I havent tried the carb cleaner to see if the engine bogs anywhere, the coil pack, I never got a recall notice nor is there one listed for my car on the mazdausa web site, the intake manifold gasket, need to check that one out, but when my header was installed last year I had a gasket replaced when the header was installed, but I dont know if that was the intake manifold gasket. Any ideas? Thanks Nik

Nik-
The exhaust change doesn't change the intake manifold - so it is still a possible suspect.

In order:
-Vacuum leak
-Intake gasket leak
-EGR valave

Let us know what fixes it!

Have you checked the O2 sensors and Mil fix? (I'm assuming you have one)

I own a 99 ES as well and I have had all sorts of trouble with rough idle. I've tried cleaning the MAF sensor, original plugs and wires, PCV valve.... no help. I got fed up and took to my local dealer and they found a vacuum leak at the Intake manifold. They replaced the Gasket to the Intake manifold and the throttle body. I have been fine ever since......

Yeah sorry I should have mentioned that earlier, both O2 sensors have been replaced within the past 3 months. I have had a CEL since about 500 or so miles on the header. I have tried 2 different Ponyexpress mil eliminators, I have tried various combinations of the manual CEL fix according to Acids instructions, and the latest thing I tried was the mechanical CEL fix, I have veilsters MIL eliminator on the way and will install it with the intake manifold gasket, last time I had the CEL read I believe it was throwing 2 codes, one was the typical O2 sensor not reading or no activity detected, and I believe the other code was the one about bank one lean or something which I believe has to do with the intake gasket. Im looking into the price of a gasket now and I will keep you informed. Thanks Nik

The gasket is cheap, it's the labour that kills.

I was quoted by my dealer $28 for the gasket and $260 for the install.

So I did it myself. (Now that is another story I'll tell if you want to do it yourself!)

Did you do the leak test yet with the carb cleaner/starter fluid spray along the top of the manifold at idle?

I just bought 99lx with 64K miles on, it was a repo I got it at $4900 I think it was a good deal.

I went thru whole bunch of maintnance work on it since last week;
Engine flush and oil change
Tranny ATX flush
K&N drop in filter
NGK iridiums
Flush power steering
new 15" alloys with 205 50 Khumo 712's

Small 1.6l is a very smooth engine but it does not will to rev really quick so to reach it's sweet spot at around 5K rpm in first second gear it takes quite long to get to it what really slows down cars acceleration do you think advance timing would work on this engine as it does on Miata's 1.6l???

Also I did notice that from time to time car idles rough?
When I bought it, it threw CEL and dealer repalced a MAF (as a recall work) CEL is gone for good but occasional rough idle is still there, it make the whole car shake and stumble so far it did not die during it but rpm jumps up and down when it happens.

Any ideas, or inexpencive ways to wake this little 1.6l up and any ideas about rough idle?

No Im going to do that this weekend, Ive been so damn busy plus its been so cold that I havent wanted to sit with my head under the hood for any length of time. BTW does any body have a pic that could show me where to spray? I think I know where but I just want to make sure. Thanks Nik

Sounds like the same thing i had with my car...

after driving around, i would turn off my car and then come back to it a few minutes later, start it, and then it would start normal, but like 2 seconds after the start when the needle base idles at 600, it would dip lower to 400 or so for only a brief second.

If this sounds exactly what you had let me know.

I pulled my hair out trying to figure out what the problem was ... till i figured it out.

Question for you do you have any aftermarket audio system in your car... or have anything that gives a high power draw. get a voltage meter and apply it to your battery and see what your charge level is. it may have something to do with your power draw, iwould notice that if i was playing my stereo loud, the voltage would settle below 13.50 volts or close to that, when you started the car the alternator does something funny Mazda says, when they did that charging system check... and this only happens when its warm? go figure

they said its nothing to worry about, if thats what is going on with your car...

let ,me know...

also check to see what your idle does when the Rad Fan Kicks in, see if it dips when that goes off and on? thats a sign of it

Just a couple of ideas...

I recently had rough idle in an Escort/Tracer. Different engine, but the fuel filter is very similar. Its between the engine and firewall, metal cylinder on the fuel's hard lines...hard to get to...at 60K I couldn't change it with plugs and wires so I had to get a shop to do it...It Helped!...later 10(-ish) oz of Berryman's Chemtool in a full tank and a 2-hour trip helped some more (the toxic paint stripper Roddimus recommended ... actually works unlike some fuel injector cleaners)

Did you change plug wires with the spark plugs? Are they still good? If its not this simple maybe it could be the Bypass Air Valve needs replacing, or the Throttle Position Sensor has a problem if you've been having sensor trouble (I think its on the IA Throttle Body) Don't ask me how to replace/fix those, I'm not an expert.

Or maybe its just your mods causing your engine to "lope" at idle speed :)

Not sure if this is it cause I dont have anything but the stock sound system. I do the Catz Zeta system on my headlights with PIAA 8000k spark blue bulbs but not sure if this would cause the same problems and I dont have them on all the time. Also I have an Optima redtop battery that is about 3 years old with a full ground kit with Monster wire connectors on the battery. Plug wires seem good they are Magnecor 8.5mm wires and they are about three years old as well. Im running out of ideas but Im stickin with the intake manifold check right now.

Rough idle gone (I hope)
 

Ok so I bought an intake manifold gasket from Mazda for 13 bucks, then I took my car to my mechanic told him to put on the new gasket and crossed my fingers. Well guess what, after all the other shit I tried this worked. Bam picked her up and no rough idle, smooth and quiet at idle rock steady and no CEL, for months now Ive lived with that horrid yellow light. Amazing what it comes down to. 13 bucks for a gasket 233.00 in labor. Damn! Anyway I probably spent too much chasing down the CEL and thinking it was my header. The first pony express performance MIL eliminator probably worked the first time I put it on but the leaking manifold was the major culprit. DAMN DAMN DAMN! Oh well live and learn. I have a question about engine vibration though. I now notice just a slight vibration being transferred back to the cabin. I have an AWR header and stock engine mounts. I noticed it more after the EGR was replaced but the ground kit seemed to smooth it out. Just wondering if a slight vibration is normal with a header. Any thoughts? Thanks Nik

I installed my OBX header on Sunday. YES, I noticed more vibration at idle. Don't think it's normal though.

Just did a search on the other forum. Lotta folks with this problem.