Morning,
I've got a SRT-4 Neon swapped Shelby charger that I've been working on for a while now. From time to time, usually after relatively hard accel's my idle RPM jumps up to around 1500 rpm (from around 900) then if I do another hard accel it may jump up again closer to 2000rpm. The problem seems to go away after I do a system shutdown/restart and the idle comes back down to around 900 as it was before the hiccup in idle speed. I've attached my MSQ and a datalog showing the strange behavior. Around 56845s the idle is normal at right around 900rpm and at about 56945s the idle comes up to around 1360rpm until after a key cycle. If anyone has seen this before and could offer suggestions as to what may be happening, I'm open to suggestions.
Thanks!
Pat
Idle goes high after hard accel
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87shelbycharger
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Matt Cramer
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Re: Idle goes high after hard accel
Try a bit less timing advance in the RPM / MAP points where the engine gets "stuck" and see if that fixes it.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
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87shelbycharger
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Re: Idle goes high after hard accel
Update:
Replaced the IAC valve under warranty and that seems to have fixed the problem. I seem to recall when I first put the old IAC in the car it actuated once when I powered the car on without the IAC being installed. I believe this is what ended up causing premature failure on the old unit.
Onto the next topic though: When the fan kicks on it is set to kick the idle up a few ticks in the IAC position. This function seems to work as expected, but instead of opening the throttle and raising the idle a bit, it actually closes the throttle a bit more (higher number) and the idle goes down. It seems that since I told the ECU that 0 steps is fully open and 255 is fully closed that the ECU software should be able to determine that in this setup to raise the idle, the IAC steps need to actually switch to a lower number instead of higher as it currently does.
Any help would be greatly appreciated. Not an entirely huge deal right now as its not causing problems, just something I noticed.
Replaced the IAC valve under warranty and that seems to have fixed the problem. I seem to recall when I first put the old IAC in the car it actuated once when I powered the car on without the IAC being installed. I believe this is what ended up causing premature failure on the old unit.
Onto the next topic though: When the fan kicks on it is set to kick the idle up a few ticks in the IAC position. This function seems to work as expected, but instead of opening the throttle and raising the idle a bit, it actually closes the throttle a bit more (higher number) and the idle goes down. It seems that since I told the ECU that 0 steps is fully open and 255 is fully closed that the ECU software should be able to determine that in this setup to raise the idle, the IAC steps need to actually switch to a lower number instead of higher as it currently does.
Any help would be greatly appreciated. Not an entirely huge deal right now as its not causing problems, just something I noticed.
Re: Idle goes high after hard accel
Are you using closed or open loop idle?
You could switch to closed loop and get the fan to kick up the rpm 100-200 rpm.
You could switch to closed loop and get the fan to kick up the rpm 100-200 rpm.
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87shelbycharger
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Re: Idle goes high after hard accel
Same MSQ as previously attached...only changes to what I was running the other night is the fuel and ign table.billr wrote:
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Matt Cramer
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Re: Idle goes high after hard accel
Both of those will affect idle behavior, and a fresh data log without the other issues to distract people will be helpful.87shelbycharger wrote: Same MSQ as previously attached...only changes to what I was running the other night is the fuel and ign table.
Matt Cramer -1966 Dodge Dart slant six running on MS3X
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87shelbycharger
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Re: Idle goes high after hard accel
Matt Cramer wrote:Both of those will affect idle behavior, and a fresh data log without the other issues to distract people will be helpful.87shelbycharger wrote: Same MSQ as previously attached...only changes to what I was running the other night is the fuel and ign table.
Matt, hat makes sense but i guess in my mind I'm not having an issue with idle. Its the reaction of the system when the fan kicks on that I'm looking to change...Here's an MSQ, not sure that I've got a datalog capturing a fan cycle (on and off). The IAC count does change to a higher number (equivalent to the fan set point)