VTPS, IAC, and Wiring questions - Miata Turbo Forum - Boost cars, acquire cats.

Welcome to Miataturbo.net   Members
 


ECUs and Tuning Discuss Engine Management, Tuning, & Programming

Reply
 
 
 
LinkBack Thread Tools Search this Thread
Old 08-05-2011, 09:58 AM   #1
Junior Member
Thread Starter
iTrader: (2)
 
Join Date: Nov 2010
Location: NoVa
Posts: 163
Total Cats: 0
Default VTPS, IAC, and Wiring questions

All,
I have a TEC-2 standalone controlling my 1.6L miata with a 1.6 Auto throttle body. Currently the IAC is controlled by the factory ECU, everything else (fuel/spark/O2, etc) is controlled by the TEC-2.

I had originally wired the TPS into the factory harness as such:
Manual < -> Auto

black/green < -> black/green
red < -> green/red
green/white < -> red
Tec-2 TPS < -> red/black wire

Where the left column is the factory harness and the right side was the sensor side of the wiring.

Admittedly this wasn't right and not providing me good resolution as the TEC-2 would show between 0-1.6v output from closed to WOT. So working through the factory manual and using a 5V output from the tec-2 we provided 5v, ground, and VTPS signal to the tec-2 and cut the OE ECU out of the loop.

Initially this worked great, and TPS was good. However now when starting the car, it will start and die at any attempt to idle. My question is this: If the factory ECU doesn't see a TPS signal on startup, will the IAC act erratically? This car was running fine, no map changes, it has just gotten progressively worse the more I've driven it since the change. I can put it back to the prior wiring but wanted to get it "right".

-Greer

tldr: Changed TPS wiring, factory ecu doesn't see TPS, will this cause IAC issues?
g_reichow is offline   Reply With Quote
Old 08-05-2011, 10:28 AM   #2
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,892
Total Cats: 1,792
Default

it really shouldn't cause issues, only that the stock switch doesn't tell the ECU that much. But in this case, the stock ECU is providing the power for the varible resistor on the TPS, since you connected the green/red and red wires together; so that's probably the issue.

the green/red is the signal back to the stock ECU that tells it if you're at 0% TPS or not. The input floats high (12v) until the the tps grounds, then the ECU knows you're TPS is closed.

The RED wire on the vtps is supposed to be the 5v source, so putting it at 1N on the wiring harness probably is messing up the signals.

I'd rewire it like this:
RED should match RED.
BK/GRN should match BK/GRN
GRN/RED should have it's own 5v source.
and RED/BK should go back to the TEC-2.
Nothing on GRN/WHT


This way the stock ECU will know when you're at idle and "part throttle", the tec-2 will get the corect 0-5v signal and all will be well in the world.
Braineack is offline   Reply With Quote
Old 08-05-2011, 01:56 PM   #3
Junior Member
Thread Starter
iTrader: (2)
 
Join Date: Nov 2010
Location: NoVa
Posts: 163
Total Cats: 0
Default

Thanks for the reply. I'll try moving those around tonight. We did rewire it already but I was concerned that the lack of a throttle closed signal was causing it to stall right after startup.

I'll try to get new wiring diagram mapped tonight. I just can't figure out why it wants to stall out of idle. I need to get this thing through emissions in next couple weeks.

Thanks!
g_reichow is offline   Reply With Quote
Old 08-05-2011, 02:03 PM   #4
Boost Czar
iTrader: (61)
 
Braineack's Avatar
 
Join Date: May 2005
Location: Chantilly, VA
Posts: 72,892
Total Cats: 1,792
Default

there's a 5v source on the AFM connector FWIW.
Braineack is offline   Reply With Quote
Old 08-05-2011, 03:14 PM   #5
Junior Member
Thread Starter
iTrader: (2)
 
Join Date: Nov 2010
Location: NoVa
Posts: 163
Total Cats: 0
Default

I've got 5v sources to spare via the TEC-2 (including one that drives the MAP right next to the throttle).

just seems weird that this rewire would work initially then cause the car to not run on after startup. I'll correct this then worry bout other things (3y.o. fuel for instance)

-Greer
g_reichow is offline   Reply With Quote
Old 08-07-2011, 04:33 PM   #6
Junior Member
Thread Starter
iTrader: (2)
 
Join Date: Nov 2010
Location: NoVa
Posts: 163
Total Cats: 0
Default

Verified the wiring that wasn't the issue. Got a good datalog with the TEC-2 and using the engine monitor I added a 40% Gamma offset and the thing stayed running. So I know I have old fuel in the tank (closer to 4 years old now that I do the math). So either I have a dirty fuel filter, incombustible fuel, or fouled injectors. I'll drain the fuel, put fresh in, and change the filter first.

-Greer
g_reichow is offline   Reply With Quote
 
 
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
Buzzing from driver side of engine bay? (MS3 install) nick470 MEGAsquirt 7 06-16-2017 02:53 PM
My solution for Oiltemp and Oilpressure input into Megasuirt (MS3) Zaphod MEGAsquirt 41 01-24-2016 01:25 PM
MSPNPPro-MM0105: Coolant Temperature Output slomiata MEGAsquirt 5 10-07-2015 02:11 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


Thread Tools Search this Thread
Search this Thread:

Advanced Search

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 11:21 AM.