DIY PROM Do It Yourself PROM chip burning help. No PROM begging. No PROMs for sale. No commercial exchange. Not a referral service.

P to D idle transition: Cause and Effect?

Old 07-10-2019, 09:30 AM
  #1  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
P to D idle transition: Cause and Effect?

Okay, so I'm pretty much happy with my part throttle cruise, WOT tune. Idle in gear is good. Idle out of gear is good. What I can't seem to solve is the park to drive (or reverse) transition. I have searched this forum till I'm half-blind and cannot seem to solve this puzzle. I can make it worse but can't seem to get it where it should be. Out of gear, idle at 800 rpm (I increased the park addition to 200 in hopes of helping the transition) IAC counts of 5 to 8. Drop it into gear and rpm drops right past 600 rpm (commanded) to 475 rpm, then finally climbs back up to 600 and stabilizes. SA jumps to 20 degrees, where it hits the limiter (15 base plus 5 idle speed error), but rpm continues to fall until the IAC finally increases and "saves" it from stalling. Since I have the Bosch III injectors, the low pulse width offsets are all zero'd out. Also, I noticed that the IAC counts don't seem to be much different in gear or out. Seems like I should be getting more IAC counts in gear (than out) with increased load. BTW, new ACDelco IAC installed a few months ago, throttle body cleaned prior to TPI conversion.

I've tried increasing AE delta map mulitplier vs TPS and also increasing low rpm SA (which made it worse, if anything). Is this a fueling problem made worse by increasing SA, or is this a SA problem not getting enough fuel?

rt66er is offline  
Old 07-10-2019, 09:59 AM
  #2  
Moderator
iTrader: (1)
 
Join Date: Mar 2002
Location: Chasing Electrons
Posts: 17,373
Likes: 0
Received 2 Likes on 2 Posts
Car: check
Engine: check
Transmission: check
Re: P to D idle transition: Cause and Effect?

IAC step count is too low. Get it into the 20 - 25 step range by adjusting the idle stop screw. This is on a warm engine and no other loads.

Note that the $8D code on a stall saver sets the SA back to the base setting. It does this by opening the EST/BYPASS line to the ICM. Can disable this 'feature:'

https://www.thirdgen.org/forums/diy-...ver-sa-8d.html

RBob.
RBob is offline  
Old 07-10-2019, 11:52 AM
  #3  
Supreme Member
iTrader: (20)
 
Orr89RocZ's Avatar
 
Join Date: Sep 2003
Location: Pittsburgh PA
Posts: 24,182
Likes: 0
Received 6 Likes on 6 Posts
Car: 89 Iroc-z
Engine: Twin Turbo 401
Transmission: TH400
Axle/Gears: 4th gen 12 bolt 3.42
Re: P to D idle transition: Cause and Effect?

Curious what the afr does when you transition? Does it richen alot cuz that could make the rpm drop
Orr89RocZ is offline  
Old 07-10-2019, 12:06 PM
  #4  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
Re: P to D idle transition: Cause and Effect?

Originally Posted by RBob View Post
IAC step count is too low. Get it into the 20 - 25 step range by adjusting the idle stop screw. This is on a warm engine and no other loads.

Note that the $8D code on a stall saver sets the SA back to the base setting. It does this by opening the EST/BYPASS line to the ICM. Can disable this 'feature:'

https://www.thirdgen.org/forums/diy-...ver-sa-8d.html

RBob.
Thanks, I'll close the throttle a bit to get the counts up; hope it's that simple.

I don't think it's hitting the stall saver threshold (350 rpm) but I'll keep an eye on it.
rt66er is offline  
Old 07-10-2019, 12:08 PM
  #5  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
Re: P to D idle transition: Cause and Effect?

Originally Posted by Orr89RocZ View Post
Curious what the afr does when you transition? Does it richen alot cuz that could make the rpm drop
Target AFR remains unchanged. O2 sensor appears to (pretty much) continue normal swings.

rt66er is offline  
Old 07-10-2019, 12:30 PM
  #6  
Supreme Member
iTrader: (20)
 
Orr89RocZ's Avatar
 
Join Date: Sep 2003
Location: Pittsburgh PA
Posts: 24,182
Likes: 0
Received 6 Likes on 6 Posts
Car: 89 Iroc-z
Engine: Twin Turbo 401
Transmission: TH400
Axle/Gears: 4th gen 12 bolt 3.42
Re: P to D idle transition: Cause and Effect?

Injector pulse? No wideband
Orr89RocZ is offline  
Old 07-10-2019, 01:11 PM
  #7  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
Re: P to D idle transition: Cause and Effect?

Originally Posted by Orr89RocZ View Post
Injector pulse? No wideband
No wideband, injector pulse is at 2.46 when the idle speed bottoms out at 475 rpm. Injector pulse doesn't really start coming up until IAC counts increase. Injector is at 1.68 in park; eventually rises to 2.69 before leveling off at 2.32.

Last edited by rt66er; 07-10-2019 at 01:14 PM.
rt66er is offline  
Old 07-10-2019, 01:15 PM
  #8  
Supreme Member
iTrader: (20)
 
Orr89RocZ's Avatar
 
Join Date: Sep 2003
Location: Pittsburgh PA
Posts: 24,182
Likes: 0
Received 6 Likes on 6 Posts
Car: 89 Iroc-z
Engine: Twin Turbo 401
Transmission: TH400
Axle/Gears: 4th gen 12 bolt 3.42
Re: P to D idle transition: Cause and Effect?

If i look at that right it appears pulse stays roughly same at normal idle and when rpms drop its still the same meaning its too rich. This certainly would drop rpms abit imo. Pulse width should drop if rpm drops, it simply doesnt need the fuel. Whats your ve table look like at idle rpm then down to the 400 rpm range?
Orr89RocZ is offline  
Old 07-10-2019, 03:05 PM
  #9  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
Re: P to D idle transition: Cause and Effect?

Originally Posted by Orr89RocZ View Post
If i look at that right it appears pulse stays roughly same at normal idle and when rpms drop its still the same meaning its too rich. This certainly would drop rpms abit imo. Pulse width should drop if rpm drops, it simply doesnt need the fuel. Whats your ve table look like at idle rpm then down to the 400 rpm range?
I've been working off the assumption that it's too lean. When I add advance, it gets worse, not better. Here's the current VE table...
rt66er is offline  
Old 07-10-2019, 06:05 PM
  #10  
Supreme Member
iTrader: (20)
 
Orr89RocZ's Avatar
 
Join Date: Sep 2003
Location: Pittsburgh PA
Posts: 24,182
Likes: 0
Received 6 Likes on 6 Posts
Car: 89 Iroc-z
Engine: Twin Turbo 401
Transmission: TH400
Axle/Gears: 4th gen 12 bolt 3.42
Re: P to D idle transition: Cause and Effect?

Maybe try taking some fuel out and see? I ran into a similar issue on my car before and it was too much fuel. Do it in the map areas where it idles and higher, as rpms drop kpa level should increase some if it starts dropping rpm that low. Just my thoughts

whats the 3d graph look like. I see a dip already at 900 rpm 40 kpa and at 1200 rpm 40 kpa
Orr89RocZ is offline  
Old 07-10-2019, 09:00 PM
  #11  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
Re: P to D idle transition: Cause and Effect?

Originally Posted by Orr89RocZ View Post
Maybe try taking some fuel out and see? I ran into a similar issue on my car before and it was too much fuel. Do it in the map areas where it idles and higher, as rpms drop kpa level should increase some if it starts dropping rpm that low. Just my thoughts

whats the 3d graph look like. I see a dip already at 900 rpm 40 kpa and at 1200 rpm 40 kpa


Thanks, I'll need to look into that for sure. As I said, I've been thinking all along that it's going lean. Here's the VE graph...
rt66er is offline  
Old 07-10-2019, 09:26 PM
  #12  
Supreme Member
iTrader: (20)
 
Orr89RocZ's Avatar
 
Join Date: Sep 2003
Location: Pittsburgh PA
Posts: 24,182
Likes: 0
Received 6 Likes on 6 Posts
Car: 89 Iroc-z
Engine: Twin Turbo 401
Transmission: TH400
Axle/Gears: 4th gen 12 bolt 3.42
Re: P to D idle transition: Cause and Effect?

It very well could be going lean. For one, i would smooth out those valleys between peaks and vice versa. Lines from low rpm to high should rise smoothly to peak torque rpm and then taper off some to peak hp, depending how far peak trq is from peak hp rpm lol but in general things should smoothly transition. Yours is abit rough

The idle area and lower rpms to 400, that ve area is a fairly steep slope down so it could be goin somewhat lean and dying off a bit

you can try either way, increase the ve in the 400 and 600 rows to get it abit closer to your 800 values, so the slope isnt as steep there and see if that helps. If not maybe try less fuel but looking at the table it very well could be too lean

fast acting wideband may show some hints there, but the pulsewidth not changing seemed suspect to me as rpm dipped. That was implying rich imo
Orr89RocZ is offline  
Old 07-10-2019, 09:31 PM
  #13  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
Re: P to D idle transition: Cause and Effect?

Seems which ever way it needs to go, I'll wind up doing the opposite first! Appreciate the input.
rt66er is offline  
Old 07-11-2019, 10:40 AM
  #14  
Moderator
iTrader: (1)
 
Join Date: Mar 2002
Location: Chasing Electrons
Posts: 17,373
Likes: 0
Received 2 Likes on 2 Posts
Car: check
Engine: check
Transmission: check
Re: P to D idle transition: Cause and Effect?

Why do the IAC steps decrease first as the RPM is dropping?

RBob.
RBob is offline  
Old 07-11-2019, 11:35 AM
  #15  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
Re: P to D idle transition: Cause and Effect?

Originally Posted by RBob View Post
Why do the IAC steps decrease first as the RPM is dropping?

RBob.
I think that's the $10,000 question. Makes no sense. Also notice the SA drops immediately before RPM drops from 15 base to 10 degrees, then jumps to 20 degrees (where it hits the SA Idle advance adder limit); it seems to happen as the shifter is moving out of park, but isn't into gear just yet. I know there's a signal to the ECM for "Park"; so when it "sees" the out-of-park signal, it cuts SA. Why?
I bumped up VE in low rpm/low kPa table and closed the throttle blades a bit more to try and increase IAC steps. Seemed to help. Should I try giving the Idle Spark Advance Vs. Idle Speed Error a little more headroom? Latest data log attached.

Last edited by rt66er; 07-11-2019 at 11:41 AM.
rt66er is offline  
Old 07-11-2019, 12:13 PM
  #16  
Supreme Member
iTrader: (20)
 
Orr89RocZ's Avatar
 
Join Date: Sep 2003
Location: Pittsburgh PA
Posts: 24,182
Likes: 0
Received 6 Likes on 6 Posts
Car: 89 Iroc-z
Engine: Twin Turbo 401
Transmission: TH400
Axle/Gears: 4th gen 12 bolt 3.42
Re: P to D idle transition: Cause and Effect?

Whats the spark table look like
Orr89RocZ is offline  
Old 07-11-2019, 01:33 PM
  #17  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
Re: P to D idle transition: Cause and Effect?

Originally Posted by Orr89RocZ View Post
Whats the spark table look like
SA lower table; keep in mind that this is an LO3 TBI 5.0 converted to TPI.
rt66er is offline  
Old 07-11-2019, 01:58 PM
  #18  
Supreme Member
iTrader: (20)
 
Orr89RocZ's Avatar
 
Join Date: Sep 2003
Location: Pittsburgh PA
Posts: 24,182
Likes: 0
Received 6 Likes on 6 Posts
Car: 89 Iroc-z
Engine: Twin Turbo 401
Transmission: TH400
Axle/Gears: 4th gen 12 bolt 3.42
Re: P to D idle transition: Cause and Effect?

Eh i honestly would make everything in the 400-800 rpm rows 15 deg. Going into gear will increase load aka higher map which will use less timing in the table which lowers torque against the converter which will slow rpm

unless that table is not used and a closed throttle spark table is used?

Basically find a stock 305 tpi bin spark and try that in those lower rpm cells
Orr89RocZ is offline  
Old 07-11-2019, 03:08 PM
  #19  
Member
Thread Starter
 
Join Date: May 2012
Location: Arcadia, OK
Posts: 142
Likes: 0
Received 1 Like on 1 Post
Car: 1990 Pontiac Firebird Formula
Engine: LO3 305 SD TPI Conversion
Transmission: 700R4 Auto
Axle/Gears: 3.23 Posi
Re: P to D idle transition: Cause and Effect?

Originally Posted by Orr89RocZ View Post
Eh i honestly would make everything in the 400-800 rpm rows 15 deg. Going into gear will increase load aka higher map which will use less timing in the table which lowers torque against the converter which will slow rpm

unless that table is not used and a closed throttle spark table is used?

Basically find a stock 305 tpi bin spark and try that in those lower rpm cells
Yeah, the Closed TPS SA table is stock AXXB, so it's 15.47 from 0 to 800 rpm.
rt66er is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
Saculia
Body
6
11-20-2012 01:09 AM
oldred95
DIY PROM
6
11-11-2007 02:14 PM
Hg
Tech / General Engine
11
03-10-2002 09:34 PM
Bjase
TPI
16
10-26-2001 05:00 PM


Thread Tools
Search this Thread
Quick Reply: P to D idle transition: Cause and Effect?


Contact Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: