AFM removal, GM IAT install, runs like crap - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


MEGAsquirt A place to collectively sort out this megasquirt gizmo

Reply
 
 
 
LinkBack Thread Tools
Old 03-05-2009, 03:13 PM   #1
Junior Member
Thread Starter
iTrader: (6)
 
Join Date: Jan 2006
Location: St Johns, Fl
Posts: 378
Total Cats: 0
Default 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.

Specs:
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:

  1. Turned car on and made sure I was getting good readings on everything in MT (stock IAT showed 65 or right around ambient).
  2. Changed settings for GM IAT in Easytherm (using 1450 bias since I'm sharing with stock ECU) and reloaded my firmware and MSQ.
  3. 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.
  4. 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.
  5. Crank car and it runs like crap. Idles low and any throttle input makes it stutter like it's missing a cylinder.
  6. 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.
  7. 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.
  8. 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).
  9. 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!
clay is offline   Reply With Quote
Old 03-05-2009, 03:32 PM   #2
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,854
Total Cats: 1,788
Default

Braineack is offline   Reply With Quote
Old 03-05-2009, 03:56 PM   #3
Junior Member
Thread Starter
iTrader: (6)
 
Join Date: Jan 2006
Location: St Johns, Fl
Posts: 378
Total Cats: 0
Default

I'll try it tonight. Thanks.
clay is offline   Reply With Quote
Old 03-05-2009, 10:09 PM   #4
Junior Member
Thread Starter
iTrader: (6)
 
Join Date: Jan 2006
Location: St Johns, Fl
Posts: 378
Total Cats: 0
Default

New firmware didn't help anything. I got to thinking about it and checked my emissions sticker and sure enough it's a Ca 93 car. Pulled the ECU out and I have two thick wires coming from ECU pins 2Y and 2Z. I guess this whole time I thought I was running on MS, I was only controlling 1/2 the injectors. Unplugging the AFM must have caused the ECU to mess up on it's half of the injectors causing my stumble and miss. Well, now I just have to figure out how to wire the other two injectors in. I'll let you guys know how it goes.
clay is offline   Reply With Quote
Old 03-05-2009, 10:43 PM   #5
Boost Pope
iTrader: (8)
 
Joe Perez's Avatar
 
Join Date: Sep 2005
Location: Chicago (Over two miles from Wrigley Field. Fuck the Cubs. Fuck them in their smarmy goat-hole.)
Posts: 26,317
Total Cats: 1,914
Default

Connect the green/white wire at 2Y (Inj3) in parallel with the yellow wire at 2U (Inj1). Connect the green wire at 2Z (Inj4) in parallel with the yellow/black wire at 2V (Inj2). Done.
Joe Perez is offline   Reply With Quote
Old 03-06-2009, 12:02 AM   #6
Junior Member
Thread Starter
iTrader: (6)
 
Join Date: Jan 2006
Location: St Johns, Fl
Posts: 378
Total Cats: 0
Default

Thanks Joe. I just wired it up and it's running great with my GM IAT. It's just sitting by my airbox, but I'm going to redo the piping tomorrow.

I guess now I know why my Warm up enrichments didn't seem to make much of an impact. Also, VEAnalyzer kept outputting maps that caused some hesitation causing me to go back to my previous best map. Now I can see that was likely because MS was only controlling half the injectors. I actually can't believe I got it running as well as I did. The PNP base map must be pretty darn close to the factory map.

Now I can do some real tuning!
clay is offline   Reply With Quote
Old 11-19-2010, 11:41 AM   #7
Elite Member
iTrader: (12)
 
Join Date: May 2007
Location: Austin, TX
Posts: 1,923
Total Cats: 0
Default

Quote:
Originally Posted by Joe Perez View Post
Connect the green/white wire at 2Y (Inj3) in parallel with the yellow wire at 2U (Inj1). Connect the green wire at 2Z (Inj4) in parallel with the yellow/black wire at 2V (Inj2). Done.
I know this is an old post, but would doing this also work to allow me to run an oem ECU from a non California spec car in a 1993 California spec car without making any other changes?
JayL is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Another Cast Manifold Corky Bell Prefabbed Turbo Kits 18 11-22-2016 10:01 PM
Are my coils failing? viriiguy General Miata Chat 5 09-28-2015 08:39 PM
wiring wideband ground to battery terminal btabor ECUs and Tuning 10 09-28-2015 06:33 PM
Missing/knock at idle, can someone point me in the right direction? Mikel MEGAsquirt 4 09-28-2015 05:46 PM


Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -4. The time now is 01:14 PM.