strange Idle issue???

[Spiced MSP]

that hose on the IAC is a coolant line. There is that line and there is another coolant line on the lower portion of the throttle body so coolant can flow around the throttle body to pretty much help the throttle body warm up when in very cold areas, especially during winter time so nothing can potentially freeze up like the throttle plate.
But it has already been proven that it doesn't really matter if coolant flows through it or not. A lot of people do a "throttle body coolant bypass" and some claim to have noticed a difference in temp when it comes to touching the manifold and throttle body. I have done the bypass and haven't had any issues with it. I see that feature as just something else for coolant to flow through..lol. No real benefit, I know it's there for a reason. But nobody has ever report any negative feedback from doing the bypass. A lot of domestic guys do it too

here is a pic of an extra throttle body I have laying around. You can see the other fitting for the lower coolant line

 

[kammokid]

Thanks agian guys, the more information the better! Sounds like i should be more focused on my coils then. The car does rev higher on a cold start up, then idles normal once warm. Its just that intermittant problem where either the brief loss of power on the highway or the sudden drop in rpm's at the stop sign, the engine light flashes then goes solid once the idle returns to normal. I have ordered the cheapie coils from rockauto and will report back after the install.
Seems I am always popping the hood on this thing which is fine, its just there are too many other projects on the go to be appreciating these continuous issues. Its too bad because mazda has a lot to offer in a vehicle. The only reason I did not go honda or toyota this time is I wanted a full load hatch back (power group, a/c sunroof) and mazda had it all in the 'under 3 grand' price range. And they are a dang fun rig to drive!

 

[Spiced MSP]

flashing is definitely a misfire so yeah coils should fix it. The high idle when you first start the car is part of the cold start warm up. It's just to help with cold start fuel enrichment. Since fuel doesn't atomize well when cold, more fuel is injected to compensate for it. and of course, with more fuel being injected, more air is needed for a proper mixture which is where the IAC comes in the picture...end result? high idle. Once the car starts to warm up, the IAC gradually closes and less fuel is injected lowering the idle until the car reaches operating temp

 

[Stiki]

I have the same problem as you..lean bank one and maf sensor code..its nt the maf sensor as I tested and replaced it anyway..check your charge pipes for hairline cracks..because it will throw that code

 

[Installshield 2]

oh ok, spiced...i didn't know that was for coolant...the only time i put a different engine in we had capped that off already, and just used a hose-to-hose fitting back there...I couldn't remember if those hoses connected to the IAC, or just the TB from underneath...its been a while haha...and agreed, i didn't have any TB related problems from a coolant by pass...although, i didn't try to drive around at sub-zero temps...

as far as the IAC and cold start...yeah, the IAC lets in more air without a need to physically move the pedal...which is why newer electronic 'drive by wire' systems don't need ANY kind of IAC...a motor just adjusts the physical position of the plate, rather than having a valve mounted that controls by pass...

Technically, FS engines with VTCS aren't actually receiving more fuel for a cold start...they're just 'chocked' by the VTCS system, which richens the mixture...but the fuel delivery will stay the same...the IAC is the only air control the engine has for idle speed...so it steps open the IAC to let in a little more air volume (which then hits the VTCS system and 'tumbles')...and ignition timing is adjusted all over the place during this phase to control a proper brief high idle...after 30 seconds or so, for oil temps to rise, the IAC will begin to close a little and idle speed will fall...but the VTCS will remain open until 149 degrees of water temp is reached...and after that, its pretty much operating temp...

so the whole systems purpose is to reduce the amount of fuel needed for a cold start...the fuel map for that brief open loop cold start is relatively lean, but the VTCS system causes turbulence and proper mixing with restricted air flow...which richens the mixture without needing more fuel to do it...thus the U-LEV compliance...the map is probably set at making a near stoichiometric mixture, which is very lean for a cold start...but when VTCS blocks off the air intake partially, its brought down to something in the 10-11's most likely...and ignition is advanced to time that slow burning ratio properly...

 

[kammokid]

Ok, finally got my coils in yesterday from rockauto and slapped them in last night. Very easy install! I reset the engine light, fired it up and seemed to
idle smoothly. It fired up again this morning, drove my 52 kilometers to work (32 miles) and still no engine light....yahoo!! I did notice a slight drop in idle at times (550 rpms) and a little rough acceleration but nothing severe enough to trigger the cel. I am however left with one hoor of an exhaust rattle, probably only a matter of time before the light comes on due to a pre-cat issue? I will monitor the situation and will certainly report back on the progress in hopes to assist any other readers out there who experience these similar annoyances!!!

 

[Sport23]

oh ok, spiced...i didn't know that was for coolant...the only time i put a different engine in we had capped that off already, and just used a hose-to-hose fitting back there...I couldn't remember if those hoses connected to the IAC, or just the TB from underneath...its been a while haha...and agreed, i didn't have any TB related problems from a coolant by pass...although, i didn't try to drive around at sub-zero temps...

as far as the IAC and cold start...yeah, the IAC lets in more air without a need to physically move the pedal...which is why newer electronic 'drive by wire' systems don't need ANY kind of IAC...a motor just adjusts the physical position of the plate, rather than having a valve mounted that controls by pass...

Technically, FS engines with VTCS aren't actually receiving more fuel for a cold start...they're just 'chocked' by the VTCS system, which richens the mixture...but the fuel delivery will stay the same...the IAC is the only air control the engine has for idle speed...so it steps open the IAC to let in a little more air volume (which then hits the VTCS system and 'tumbles')...and ignition timing is adjusted all over the place during this phase to control a proper brief high idle...after 30 seconds or so, for oil temps to rise, the IAC will begin to close a little and idle speed will fall...but the VTCS will remain open until 149 degrees of water temp is reached...and after that, its pretty much operating temp...

so the whole systems purpose is to reduce the amount of fuel needed for a cold start...the fuel map for that brief open loop cold start is relatively lean, but the VTCS system causes turbulence and proper mixing with restricted air flow...which richens the mixture without needing more fuel to do it...thus the U-LEV compliance...the map is probably set at making a near stoichiometric mixture, which is very lean for a cold start...but when VTCS blocks off the air intake partially, its brought down to something in the 10-11's most likely...and ignition is advanced to time that slow burning ratio properly...

The Protege does target stoic even on cold start. I've confirmed this with my wideband (and VTCSless intake manifold.)

Ok, finally got my coils in yesterday from rockauto and slapped them in last night. Very easy install! I reset the engine light, fired it up and seemed to
idle smoothly. It fired up again this morning, drove my 52 kilometers to work (32 miles) and still no engine light....yahoo!! I did notice a slight drop in idle at times (550 rpms) and a little rough acceleration but nothing severe enough to trigger the cel. I am however left with one hoor of an exhaust rattle, probably only a matter of time before the light comes on due to a pre-cat issue? I will monitor the situation and will certainly report back on the progress in hopes to assist any other readers out there who experience these similar annoyances!!!

Give it a little time to relearn spark advance, etc. for your new coils. It should smoothen back out and run great then.

 

[Installshield 2]

The Protege does target stoic even on cold start. I've confirmed this with my wideband (and VTCSless intake manifold.)

nice, that is exactly what i thought...but i never was able to test my factory P5 computer...

i have torque pro with an elm327 and an mp3 computer...the MP3 computer targets around 10:1 for 10 seconds and idles just under 2,000 rpm, and that slowly rises up to 12.5:1 until about 30 seconds after start, where the revs drop to around 1200rpm...then closed loop comes in and it idles at near stoichiometric...and engine speed settles to around 750...

and thats what i was getting at for VTCS...the non-mp3 computer nails stoichiometric fuel wise, BUT the VTCS blocks some of the air volume, and more importantly, swirls it and changes its speed right at the intake valves...flow through the MAF remains the same, as its last second turbulence that aids the mixing, as well as the drastic increase to air speed...so even though the computer is 'making' a 14.7:1'ish mixture at the injectors, map wise...whats in the chambers behaves as if its quite richer...

its one reason i'd say VTCS with a stock computer isn't all that great...especially when ambient temps are extremely low...because without VTCS, your engine will get a very lean mixture for half a minute...not great for uniformly heating everything, and definitely not great for operating the car right after the start...the Mp3's 30 second open loop protocol for a cold start is definitely different...and i'm 99% sure the difference is because that computer isn't mapped to start with VTCS...

 

[Spiced MSP]

the car has to inject more fuel to compensate for the amount of air coming in on cold start and the fact that cold fuel doesn't atomize well. In order to achieve a stoic mixture, this has to happen. If you started the car and added more air without increasing fuel, the car will run lean and more than likely stumble a little bit from the lean mixture or maybe even stall. Im running a custom 505 aluminum manifold which of course doesn't come with VTCS or VICS and is a completely different design overall. I never really pay attention to my wideband on cold starts so I can't really chime in on that part, But the same thing is done when tuning a standalone. You let the car warm up to operating temp. Tune your base fuel and timing maps to your target AFRs. Once those are dialed in and verified on several starts and idle sessions. You let the car cool down. Then, when you try to start the car again, it will more than likely not start. That's because you then need to go back and tune your correction maps like coolant temp correction, air temp correction and things like that. Adjust those maps, more than likely by increasing fuel to compensate. On those maps, you add fuel and gradually decrease with corresponding temp on table all the way to a 0 correction value. At the 0 correction value is where the base fuel map is being used 100% without correction factors, the car is at operating temp and the IAC is at minimal output. I have verified this with my standalone on a cold and warm motor. I could start the car with no problem on a warm engine and it will start every time because minimal input from the IAC is being used. Turn the car off and let it cool off all the way. Come back outside and attempt to start the car, it would not fire at all. It would turn over a couple of times and start, but die immediately as a result of the correction maps not being setup for cold start

 

[kammokid]

Well its been a week later and 700 kms (435 miles) on my new coils. The engine light came back on solid after 130 kms (81 miles), I am guessing due to the loud and annoying exhaust rattle, most likely the pre-cat as outlined in previous posts. But the good news is, I have not experienced that messed up sporadic idle issue nor the loss of power at high speeds. The engine light is solid with no flashing whatsoever. It sometimes takes a couple of turn overs to fire up after the engine is warm but always fires right up when cold. I am taking it on a long trip tomorrow so it will be a good test. But in the meantime, nice to have the old mazda performance back! Many thanks again to all the informative posts!!!!!!!

 

[Spiced MSP]

awesome