92 mx3 gs IAC shot?

[haze]

I bought a 92 mx3 last year, ran fine for 10 months. 1 month ago i noticed my mileage was almost half of what i normally get. I usually get around 320km on 35Liters. not the greatest. But my last two fill ups have been 180km on 35L and then 180km on 40L. horrible. During the last couple weeks it has been idling horribly, RPMs rising and falling. It has stalled a couple times at a stop. One time after running for 10 minutes, then sitting for 10 minutes, it would not start again just crank and crank, and smelled flooded: it started the next morning.

I took it to the mechanic, he told me the Idle air control motor is shot. But, he said he 'bypassed it' and defaulted the idle to 1000rpm for now, so that i have a running vehicle. He said that i should still expect crappy mileage because the computer is still reporting an error. He said he did this because a new IAC motor costs $750, and a used one will still probably cost $300+ and even then it's gonna be a 18-20 year old part that will fail anyway. He knows i don't have much money to throw into this car right now.

I have a couple of questions. I am not real car guy, the most i've done is change my oil /air filter/ and tires.

Is getting a hold of a used IAC motor a viable option? what years will work with a 92 mx3 gs?

Is it possible/recommended to run efficiently without an IAC?

Is there even such a thing as 'bypassing' the IAC? He made it sound like he got the IAC still working to some degree, upping the rpms to 1000 to prevent stalling, but not lowering them back to 600rpm or whatever it is.

Thank you for any insight.

[mikeinaus]

the iac is a valve not a motor. as far as i know it just helps control the idle and i dont think it would affect your gas mileage that much. im not 100% sure but i think you can grab one from any obd1 1.8l v6 92-95, obd2 (95-97) may work aswell but i doubt it.

yes it is possible to bypass the valve, it has a plug on the top and all you need to do is unplug it, its extremely simple. bypassing the valve takes away the computers control of the idle.

yours may just be clogged and not broken. its located on the battery side of the throttle body with a white plug going into a black cylinder on a metal body. if you remove the valve you can try cleaning it with brake cleaner and see if it helps. if not this is a decent deal, and will also show you what the valve looks like. its a very simple procedure and i highly suggest you attempt it yourself. it shouldnt take more then 30min to an hour and should save you quite a bit on labor. thres 2 coolant hoses to remove and 2-3 bolts. http://cgi.ebay.com/ebaymotors/92-94-Ma ... ccessories

$300+ for a used valve is a complete ripoff. i got my entire motor for under $200 from a wrecker. if you have any local wreckers im sure you could get the valve for anywhere between $5 and $50 at the most.

[Ryan]

I'd get a new mechanic...

There is no way your IDLE affects your mileage that much, unless you idle your whole tank away, which would net you 0 MPG anyway. Plus, hot idle is 700, not 1k.


Do the free stuff: Check the intake for cracks/leaks(especially the accordion section), check the coolant level. Follow this link and see what codes your car is throwing, aside from IAC: http://www.mx-3.com/phpBB3/viewtopic.php?f=23&t=34787 This takes maximum 10 mins even if you've never done it before.


replace plugs/wires/cap/rotor. Right there you spent less than $300 and will probably fix the issue.

If you have access to the tools for free or cheap (or want to pay a mech again), reset the idle (after you fix whatever the mech did to the IAC, which was probably fine) and reset the ignition timing with a timing light.


Report back with your findings!

[mitmaks]

Ebay usually has decent deals on used ones
http://cgi.ebay.com/ebaymotors/92-94-Ma ... ccessories

[haze]

Guys, thanks alot for the help.

I checked the codes, and the only thing that came up is : 24 RHO2S inversion error .
SO my o2 sensor is spent? From what i read, if that is the case, it causes the fuel ratio to richen up, causing shitty mileage. Also, could that be why it was idling shitting and stalling out? too rich...

Does that mean he cleared the the IAC code out or is it possible it never came up.

Thanks for the eBay auction link too, if that ones $50 i'm sure that i can find a cheaper IAC at a wrecker if that is even the problem. What the hell is my mechanic talking about $300 for a used one...

I checked the intake for leaks, but i'm not exactly sure i did it right. I inspected the main black accordion section with a light, and then ran the motor and sprayed water on it and checked for any bubbling. I didn't find anything, it looked fine to me.

[haze]

I talked with my mech again, tried to get a break down of the labour he did, he was vague and kept changing the subject to how we should proceed instead.

He said his computer gave him the error codes for EGR and IAC, and he tested the wiring and the MAF. I asked him what specifically did he do to the IAC, he said the wiring to the IAC was higher resistance than normal but not horrible, but he didn't do anything to it. His stance is that the IAC was pulling the idle down so low that it was stalling (bullshi*?). He keeps saying he wants to look into it further, well isn't that why i left my car there all day in the first place?

I told him that i found the code 24 RHO2S inversion error, he said thats probably not causing the problem, that all it means is the sensor is too slow and its going back and forth. but later then admitted to wanting to check it out and test it.

I said i could get a cheap IAC , he asked "new or used" . I said used, and he said not to do that yet, because we need to look into it further. This leads me to believe that the IAC was never the problem , he just upped my throttle to get me on my merry way, ran out of time to really figure out the issue, and charged me $260 for labour.

[haze]

my replies are not being approved ???

pulled the codes and got a 24, RH02S. got my mech to test front and rear sensors and they were both fluctuating from about 0.1 up to 0.9. He said that is how they should function.

so he cleared the codes and is telling me to drive it and see if it comes back. if it does, its probably a problem with my wiring or ECU?

[Mr.mx-3]

or just go to the junkyard and get one from any K series motor had to barrow the one off my ZE to put on my K8 to get me by until I could afford to swap.

[davmac]

I agree that jy is best place for a replacement IAC. If you do not have a pull your own parts place then you'll likely have to buy a throttle body from a salvage yard and get the IAC with it. $30 - 40 for the throttle body. An option might be to post a want to buy at this site.

Unfortunately you have to be aware that IAC are fairly specific to how they mate with the throttle body. IAC from a KLDE or KLZE are interchangeable with a few minor tweaks but you can't use the IAC from a KLDE or KLZE on your K8 - it won't mate to your K8 throttle body.

For pics and more info on compatibility check here. There are several links to pictures so you can see what you're looking for. The IAC is attached below the throttle body and does, in fact, look like a little motor.

I don't know where you live or what you need exactly, but PM me as I might have a K8 throttle body and IAC that I would sell.

[Mr.mx-3]

I agree that jy is best place for a replacement IAC. If you do not have a pull your own parts place then you'll likely have to buy a throttle body from a salvage yard and get the IAC with it. $30 - 40 for the throttle body. An option might be to post a want to buy at this site.

Unfortunately you have to be aware that IAC are fairly specific to how they mate with the throttle body. IAC from a KLDE or KLZE are interchangeable with a few minor tweaks but you can't use the IAC from a KLDE or KLZE on your K8 - it won't mate to your K8 throttle body.

For pics and more info on compatibility check here. There are several links to pictures so you can see what you're looking for. The IAC is attached below the throttle body and does, in fact, look like a little motor.

I don't know where you live or what you need exactly, but PM me as I might have a K8 throttle body and IAC that I would sell.

I must've been lucky because i used the IAC from my ze on my k8 and it mated fine for me no leaks no problems just used the whole bottom plate the motor/valve was mounted to same bolt pattern same everything but I will mention mine is a curved kneck ze

[haze]

why cant i reply to my own topic? this is frustrating.

[davmac]

I must've been lucky because i used the IAC from my ze on my k8 and it mated fine for me no leaks no problems just used the whole bottom plate the motor/valve was mounted to same bolt pattern same everything but I will mention mine is a curved kneck ze

Edit: I take that back - nothing lines up (coolant passages or air passages) between the K8 throttle body and IAC from a DE or ZE but the bolts will match. But what the heck if it worked for you then I'm not going to argue. Sometimes preference for one IAC over another is interference with the coolant hoses or the electrical connector that run to the IAC. Each K motor has connectors set up a specific locations and angles to accommodate the engine compartment design.

[haze]

my replies finally showed up ^^ please read above.. guess there was a bug in the messageboard system.

mechanic cleared the codes and i've driven it for about a week...really short drives...and no codes are coming up now. but still the shitty mileage, stinky smell, and this is with idle at 1k rpm. p.s. coolant level is fine

guess i'm just gonna have to take it back to the mech and see where he goes with this.. obviously the IAC isn't the problem.

[haze]

since the problem , my mileage had been about 22L/100KM mid-winter
as the weather is warming up to about 12C nowadays , my mileage is increasing. my last tank from april went 13.4L/100KM . still this isn't as good as it should be. i was getting around 10L/100KM last summer.

and actually as i look back at my mileage through last year, the hotter the weather the better my mileage it seems.

does that narrow the problem down?

[davmac]

The bad mileage and the surging idle all point to the coolant temp sensor. It has a direct impact on idle speed and if it doesn't deliver the message that the coolant is warm will also cause the ecu to have the car running rich or at higher idle.

Gas mileage is typically better in warmer weather when the coolant more quickly reaches operating temp and the ecu will also drop idle and run the engine nearer to lean.

A coolant temp sensor is cheap and easy to replace so worth a shot. However your gas mileage is still being hurt some by idling at 1K when it should be 650 - 700.