High Idle and misfire
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Author:  Stefenwolfe [ December 10 2015, 10:30 AM ]
Post subject:  High Idle and misfire

So lets start from the beginning here:

-On December 3, 2015 the larger hose that goes from the IAC to the intake broke, and during this time, I also had some tps issues, so I made a trip to advance auto.
-I took my whole aftermarket intake off for more room and all so everything would be easier
-I figured since im already here, why don't I turn that tps a little (before i knew how to properly adjust)
-I did all that, put my intake back in, hoses replaced and everything so we were ready to go
-started the car, it dies, but that's what it did before I adjust the tps in the cold weather, so I thought of it as normal
-start to go down the road, and the car is lacking much much power, check engine light is on, i just thought it was the tps
-after a bit of driving it started to misfire, sputter, just not run great at all
-I got 5 miles down the road before I said to my self wtf is wrong
-I start looking around and I saw my MAF was unplugged, so I plugged that in and started the car up, still misfiring, even at idle
-I drove down the road about another 5 miles, misfiring like hell
-so I unplugged tps, thought it fixed everything but it still misfired, just not as much, so i went with it for a week

-December 9, 2015 I got down to business, I adjust the TPS using the fan method when the key is on the on position
-I Adjusted my idle to about 700rpms ins DIAG mode
-I drove all the way home (bout 20 miles from where I was) only misfired once or twice, so I figured that maybe the ECU needed a reset
-when I got home, I did the ECU reset, as far as I know, you just disconnect the negative terminal and hold the brake for a few minutes, then pug it back up and started her up. what I didn't know is that you had to let it idle for a bit, which i didn't do
-I drove another 20 ish miles and it did good, no misfire at all
-on the way back (another 20 miles) It misfired like hell again

Today is Decmber 10, 2015 and the car still misfires, sputters, and all. It Idles at 1000-1900rpms. This is strange but... at like 10-40% throttle is the only place where it misfires, if I floor it, it runs just fine

Any Ideas guys..?

Author:  4gotn [ February 12 2016, 4:22 PM ]
Post subject:  Re: High Idle and misfire

I know I'm a little late to the party here...but it looks like most everyone has evacuated the site. I notice in your sig that you have a b6... those are NOTORIOUS for having IAC issues... most of us just unplugged the damn thing when it started causing issues. You'll find that the "vics" system, EGR, and the IAC are probably the worst designs ever. I would make an attempt to clean the IAC by disassembling it from the throttle body and hosing it down with some brake parts cleaner or maybe some B12 Chem tool carb cleaner... the kind in the spray can. Ultimately, since the car is 22 years old you may want to consider doing a miata head swap and using a miata manifold. If memory serves right you'll have to reroute the intake and youll have a tight fit on the passenger side. Or you could just do a bp swap. :B

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