More ?'s about BS3 and cold start


Well-Known Member
Aug 19, 2001
I have been chasing my cold start prob. for a while now. I have everything setup just as the directions say's. I have the timing at 10 deg. In the blocks where it idles the TPS is setup right and I think the IAC is right. The problem is I have no fast idle and it's hard to start and keep running ( it wants to idle around 500rpm's) till the temp is about 140deg then it starts and idles like a champ.

I have been told a few times that I should drill an 1/8th inch hole it the TB blade and run 30deg's timing in the blocks it idles in. And I haven't found anyone that has it like the instructions. What should I do?
If the AF is not right it won;t run, 10 degree idle cold it will barely run............try about 27 degrees and an aft of 11,8 to 1 cold. Have you checked if the IAC is working???? bring your target idle speed up and down and see if it actually moves.
It idles at about 13:8:1- 13:0:1. So maybe i am to lean? I have another post up about the IAC. I am not sure if it is working and I don't know how to check it. As in the other post I tried to log it and the DES IAC was reading but the ACT IAC was at 00. I have adjusted the idle speed up and down and it does idle where ever I set it after it is warmed up

The only reason I have the blocks at 10 at idle is because that is what the manual said. I will try to put it at 27 in the blocks and see what it does. I had it at 30 once but I don't remember what the result was.
try and set the target idle to 1500 hot and see if it goes up that high, I don't know how the iac works the manual does not even show the terms actual iac position in the help section, so I would ingore that term. You want the iac to be about 10-15 counts hot idle in neutral adjust the TB screw until you get the desired iac into that position I would assume. 13.8 on a cold start is way lean.
That's one of my problems. I don't know what my IAC is at it shows 00. That why had that post I was trying to see where it was. Also I'm sorry but that AFR was at warm idle. I don't have any idea what it is at cold because the car won't stay running till it warms to 140. I have to keep revving it up to keep it running. I have had the cold start idle graph all over the place to try to get it in cold start mode. I have had it set as far as 2500 with know luck
Ok I looked and I have it at

2500 2500 2000 1500 1300 870 850
-14.8 33.8. 55.4 77.9 125 169 230

That is what the desired rpm table looks like
Also my IAC position table is

127 127 127 100 90 90 80 55
-14.8 33.8 55.4 77.9 102 125 169 230

I realize this is probably way off but it has been all over the place trying to get it to work. This was from a tune sent to me from a guy that had it on his car so I left it
You need to find your min and max rpm range with the car warm, take the idle speed and put it to 2000 and then 700 see if you can get those targets. If you can;t then adjust the blade until you can..
I have similar issues b/c I have a BS3 and have been fighting with the cold start without much luck. Here are a few things I've learned along the way, but I still can't get it to fire like it should when cold. Apologies if I'm repeating things that you know already.
  • BS3 has a DES IAC and an ACT IAC, and I think the ACT IAC always reads zero so I ignore it. The directions are completely silent on this point, but someone on asked a similar question and the answer that came back is it doesn't do anything. My confidence level in the answer is about 65%, so I only pay attention to DES IAC.
  • I thought I had a problem with the IAC, so I took mine out while plugged in then turned the key (and maybe cranked the engine I can't remember). I also bought a new IAC b/c I thought it was the cranking problem. Anyway, when I turned the key the little pintle (or whatever it is) that moves in and out shot out into the garage floor somewhere I know not. So I put the new one in, no improvement but I'm pretty sure it's working.
  • The timing at crank is the lowest left box (the first cell basically) and this shouldn't be set to 10. The example in the BS3 manual (Feb 2011 edition) is 22 degrees; let me know if you'd like me to send you a pdf of this manual.
  • The 10 degrees for timing as referenced in the BS3 manual is for idle spark setting. This is actually a pretty cool feature (not unique to the BS3). The idea here is set spark timing to 10 degrees in cells that typically idle, then calibrate the idle spark table. The manual from February 2011 walks through how to do this on pages 76-77. If the rpms drop at idle the idle spark table will advance timing, if the rpms surge it will pull timing. 10 degrees is the base, then ECU adds or subtracts timing based on the table. This only works though if you're below max idle for TPS in the Operating Parameters.
  • I've been told to give the IAC three to five seconds to open up in the throttle body before cranking.
  • My last attempt at getting a good cold start was to turn the idle screw in to try to get the idle higher generally. In doing so, I ended up stripping one of the 8mm TPS bolts in my throttle body, so I need to fix that. I think I'm chasing the same problem as you as my goal here was to increase the idle with the idle screw in the hopes that the car won't die after I crank it in the cold.
  • I also have a long crank before it fires. This very well could be my tuning (pretty much a novice), but I read somewhere on the internet (yikes!) that the BS3 doesn't batch fire like the XFI so it needs a cam signal and crank signal before it fires. I'm still hoping there is a solution for this b/c I don't like my car cranking a lot after it sits overnight (even in the summer). Makes it sound like a piece of crap.
That's what I know. I've managed to do an okay job with tuning the idle spark table so I have a good idle and I've confirmed my IAC works. I've yet to get the cold start nailed down, and I continue to dick around with cranking fuel and the IAC. It's frustrating as hell, but that's the way it goes. I also get why someone said drill that hole for a better idle, but I don't think I'd ever do that.
Wow Dukegn thanks. Sounds like we are going through the same thing. I will change the bottom box to 10 and see what it does. I have had from 20-30 with no change.
I have the manual and have read it SO many times trying to get this thing right. Mine takes a long time to crank and fire. One thing I realized when reading the manual again was when I set it up I didn't zero out my idle timing table. So I will do that today. I have read everything I can on this like the thread on YB Several times. Thanks for the help. I will post what I find out
If it's stalling when cold, it's very typically too lean. Make sure you have enough enrichment in the Warmup - MAP vs Coolant table.
I will change the bottom box to 10 and see what it does. I have had from 20-30 with no change.

If the bottom box is not ten then you are good. You don't want it to be ten at crank, more like 20-30 -- thought I would clarify.
Ok I zeroed out the idle spark table. And put 22 in the bottom left corner like the manual said. I was able to get it to idle at 2000 and then 700 but adjusting the TB screw. I now have it set back at 900 and the idle spark is still all zeroed out and the TPS is at 2.0. And it is fine. I will let it cool down and see if the cold start is better.
Went to try the cold start and its the same if not a little worse it took up to 160deg to get it to idle instead of the 140deg I was doing before. I played with the map vs coolant table it only made it worse it acted like it was flooding it out in the one direction (up with #'s) and no real change going the other way with the #'s.

I'm at a lose. Don't know what else to try. I have adjusted afterstart correction, map vs coolant, fuel,spark tables, cranking table on and on. Don't know what else to do.
Please log the air fuel ratio when it is warming up, don;t throw numbers at it. You will need about 11.5-7 af for the 1st 30 sec run time, then about 12.0 then about 12.5 then about 12.8 then by 160 13.0 then by 1.70 about 13.8. DO one change at a time..
Some of the problem is it won't run on it's own till a certain temp. I noticed that when it would run for a few seconds it was around 12:1 and bouncing up and down. But was only idling around 400-500 rpm.

I will log tomarrow when I get home. Is ther anything special you want on the log?
The ususal stuff Af ratio, rpm coolant temp, after start correction, warm up corrections, map timing. You can send me the file Ihave th BS3 program.