03-05-2009, 02:13 PM
Join Date: Jan 2006
Location: St Johns, Fl
Total Cats: 0
AFM removal, GM IAT install, runs like crap
Hey guys, I've run into a bit of a hiccup when removing my AFM on my MS1 equipped car and wanted to see if anyone had any suggestions. I already searched all the AFM posts I could find, but I'm still not sure what's going on.
93 Miata running MS1V3 with HiRes code. Parallel install, stock injectors, stock AFM, stock everything. Running great for the last two months or so on tuned MSPNP map. LC1 installed. I am fabbing up a new intake pipe to install my GM IAT and get rid of the stock AFM. To eliminate variables I decided to just unplug the AFM, wire up the GM AIT and make sure it runs OK before installing the piping. So I did the following:
- Turned car on and made sure I was getting good readings on everything in MT (stock IAT showed 65 or right around ambient).
- Changed settings for GM IAT in Easytherm (using 1450 bias since I'm sharing with stock ECU) and reloaded my firmware and MSQ.
- Unplugged AFM connector, jumpered FP to GND at diagnostics box, and plugged my GM IAT into pins 1 and 6 on AFM connector. I just let the GM IAT sit near my airbox not mounted into anything.
- Opened MT to make sure I was seeing about the same ambient temp reading with GM IAT as I had seen with the stock IAT and old firmware. 65, Check.
- Crank car and it runs like crap. Idles low and any throttle input makes it stutter like it's missing a cylinder.
- I unplug the GM IAT from the connector, remove FP jumper, and plug AFM back in and it runs great again. That's the only thing I changed. This is without touching the firmware or MSQ so the MT AIT gauge shows about 15-20 degrees higher than normal (80 or so), but it still runs great.
- Just to be sure, I unplug AFM, jumper FP, and plug GM IAT back in AFM connector. Runs like crap again. MT AIT gauge shows 65 again.
- Just to see what happens. I disconnect the GM IAT while it's running and with no IAT plugged in at all, it continues to run like crap only now the gauge in MT shows -40 or something (no signal).
- I even disconnected the intake pipe right after the AFM just to make sure nothing in AFM itself was blocking the airflow when the AFM was disconnected. No difference.
It sounds like my GM IAT isn't working properly, but I'm getting a (pretty accurate) AIT signal at the MS from the GM IAT. Still it's running like it's not getting any signal at all from the GM AIT. Any ideas?
Also, not that I think it would matter, but this is a 93 that I bought from the original owner in SoCal. I don't know if it's a CA car or even if that would make a difference. The only difference I know of for the CA 93 is different wiring to the injectors or something. I didn't notice that when I wired the MS into the harness and it's now hidden behind the floorboard again so I can't check. The fact that it ran great for months with the AFM makes me think that has nothing to do with it, but I figured I'd share in case it sparked anything. Let me know what you guys think!