No throttle response at all on hot starts. Please help!
Thread Starter
Teching In
Joined: Apr 2006
Posts: 37
Likes: 3
From: Modesto, CA
No throttle response at all on hot starts. Please help! I have an LS3 swapped ‘65 Chevelle w/T56 magnum that runs fine, until I attempt to start it warmed up after a short time shut off (example: engine normal operating temp, shutting off for 5 minutes to fuel up at gas station, then restart)
It cranks for longer than normal, then once it starts, it idles very rough with absolutely no throttle response (pedal to the floor even and it does nothing). Engine light turns on and only shows:
P0650 - MIL Control Circuit/Open
P2176 - Throttle Actuator "A" Control System
Idle Position Not Learned
In order to get any throttle response, I have to shut it off, wait usually another 5-10 minutes, then restart. Even after that, engine light still on, it still idles rough, and it just doesn’t drive right as the idle is not learned (RPMs don’t drop between shifts, idles high around 1,500rpm until the car is at a dead stop even in neutral, then drops around 900rpm)
Seem odd that it only happens after it’s warmed up, as if some electrical component is getting heat sink and failing or something. If the car then sits in the garage for a couple weeks, it starts up fine with the check engine light off as if it never happened, but will happen again the next time I make a short pit stop on the road… frustrating
(It has a fly by wire 102mm Nick Williams throttle body, PSI Stand Alone Wire Harness, and a 2008 corvette ECU that is mounted inside on the floor under the dash)
What do you guys think I should check to resolve this issue?
It cranks for longer than normal, then once it starts, it idles very rough with absolutely no throttle response (pedal to the floor even and it does nothing). Engine light turns on and only shows:
P0650 - MIL Control Circuit/Open
P2176 - Throttle Actuator "A" Control System
Idle Position Not Learned
In order to get any throttle response, I have to shut it off, wait usually another 5-10 minutes, then restart. Even after that, engine light still on, it still idles rough, and it just doesn’t drive right as the idle is not learned (RPMs don’t drop between shifts, idles high around 1,500rpm until the car is at a dead stop even in neutral, then drops around 900rpm)
Seem odd that it only happens after it’s warmed up, as if some electrical component is getting heat sink and failing or something. If the car then sits in the garage for a couple weeks, it starts up fine with the check engine light off as if it never happened, but will happen again the next time I make a short pit stop on the road… frustrating
(It has a fly by wire 102mm Nick Williams throttle body, PSI Stand Alone Wire Harness, and a 2008 corvette ECU that is mounted inside on the floor under the dash)
What do you guys think I should check to resolve this issue?
Thread Starter
Teching In
Joined: Apr 2006
Posts: 37
Likes: 3
From: Modesto, CA
[QUOTE=G Atsma;20452007]Is your ECM wired to totally shut off when the key is off? It sounds like it's relearning every time you start
It needs a 12v feed at all times, next to no amp drain.[/QUOTE
I’ll have to look into that for sure. I don’t have this problem on a cold start though (not sure if that makes a difference).. only happens when the car is started shortly after it already ran.
I’ll look into that regardless tho. Thanks.
It needs a 12v feed at all times, next to no amp drain.[/QUOTE
I’ll have to look into that for sure. I don’t have this problem on a cold start though (not sure if that makes a difference).. only happens when the car is started shortly after it already ran.
I’ll look into that regardless tho. Thanks.
TECH Fanatic
Joined: Sep 2008
Posts: 1,654
Likes: 531
I don't know this will help but.
I am assuming you are running an aftermarket LS engine harness of some type.
On one my LS swaps I had a problem similar to yours. Cold start it started right up and drove fine. Mine was DBC 2002 LS1/4L60E combo with an aftermarket harness. So after a drive it took a bit to start, ran rough and then ran fine. It was like that for about 2 months after I started driving it. No engine codes. I have a scanner. Then one day it won't start at all. So my first test was did the fuel pump run when I turned the key and it didn't. I was thinking bad fuel pump relay. I replaced it but no joy. And then as I kept cranking I could smell hot plastic from around the fuse block. Under further investigation the 12 volt ECM constant wire connection was not all the way plugged in and after warming up was arcing and creating an open circuit. It had melted a bit of the fuse block. I repaired the connection and it ran great.
Hope this helps.
I am assuming you are running an aftermarket LS engine harness of some type.
On one my LS swaps I had a problem similar to yours. Cold start it started right up and drove fine. Mine was DBC 2002 LS1/4L60E combo with an aftermarket harness. So after a drive it took a bit to start, ran rough and then ran fine. It was like that for about 2 months after I started driving it. No engine codes. I have a scanner. Then one day it won't start at all. So my first test was did the fuel pump run when I turned the key and it didn't. I was thinking bad fuel pump relay. I replaced it but no joy. And then as I kept cranking I could smell hot plastic from around the fuse block. Under further investigation the 12 volt ECM constant wire connection was not all the way plugged in and after warming up was arcing and creating an open circuit. It had melted a bit of the fuse block. I repaired the connection and it ran great.
Hope this helps.
