Cold start surging?
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From: Weaverville, NC
Cold start surging? I did some basic tuning as mentioned on here with ve tables and adding 2* of timing on lower end. Idle @950. It does not die or anything, but when you first start up cold it surges. After a few miles of driving it is fine. Is there something I could try to get that out of the car? I would love to lower the idle down some more to hear the cam but affraid of making things worse. Should i stay away from drilling the throttle body? Thanks for the help.
Last edited by 00SS4780; Jan 11, 2004 at 12:48 PM.
If your car is like mine, the surging only lasts until the PCM goes closed loop on a cold start, which is less than one minute even in the coldest weather. I think the coolant has to reach 100 degrees. This is a good time to just sit there with your foot on the pedal warming up the engine, and most importantly, the springs.
Mine started surging when I put the TCI converter in. I think
the lower rotating mass changes the "natural" frequency of
the motor at idle and makes RPM fall faster than the IAC
loop can track. I don't know whether there's any soft
setting that touches this (like a limit to IAC delta per tick).
Lean surge (lean open-loop idle) could be a contributor,
this would be what VE touchup addresses I expect.
The surging isn't as annoying as having the car die when
you pull out to the median and stop to make the first left
turn of the morning.
I may just have to follow up on my notion of adding an
idle air bleed screw to the TB.
the lower rotating mass changes the "natural" frequency of
the motor at idle and makes RPM fall faster than the IAC
loop can track. I don't know whether there's any soft
setting that touches this (like a limit to IAC delta per tick).
Lean surge (lean open-loop idle) could be a contributor,
this would be what VE touchup addresses I expect.
The surging isn't as annoying as having the car die when
you pull out to the median and stop to make the first left
turn of the morning.
I may just have to follow up on my notion of adding an
idle air bleed screw to the TB.
That idle air bleed screw would be an interesting thing to try. An idea I want to try is boring the IAC port a little bigger. I think this may help because I see the IAC counts maxing out under these conditions, yet if you make the TB blade hole any bigger, there is too much air to idle down a hot engine. The thing that is really needed is an IAC with more dynamic range. The IAC plunger is big enough to allow a larger bore without stopping it from closing all the way when it needs to.
Keep working on the idle timing and VE table.It takes a little time but you will get it to idle great..I setup the timing so it does not move at idle (like 24 degree's)this really smooths out the idle alot on real cold and hot starts.
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Originally Posted by Slowhawk
Keep working on the idle timing and VE table.It takes a little time but you will get it to idle great..I setup the timing so it does not move at idle (like 24 degree's)this really smooths out the idle alot on real cold and hot starts.
1.) Reach target RPM
2.) Reach target IAC (Steps)
3.) Reach target Spark Advance
If any of the three are out of synch it will continue to surge, as the blade (steps) increases and decreases ( TPS%), in order to "stay running".
So, we need to synchronize/ balance all three - right??
Somewhere "Idle Air" (RAF) falls in place - but where???
joel
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Along with cold starts, I have a problem getting the car to fire and stay running at all. I usually have to give it a little gas to keep it running? Any ideas? How does the computer interpret the Crank VE Settings? Or are they even relative to it starting for a split second, then dying...?
If I have to give it gas to keep it running when starting it, would it be beneficial to reduce some timing down low, therefore kinda richening it up?
Slowhawk, thats a good idea about the timing, and using just one value. I might try that out this weekend as well...
If I have to give it gas to keep it running when starting it, would it be beneficial to reduce some timing down low, therefore kinda richening it up?
Slowhawk, thats a good idea about the timing, and using just one value. I might try that out this weekend as well...
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Originally Posted by JxxxOxxxE
Along with cold starts, I have a problem getting the car to fire and stay running at all. I usually have to give it a little gas to keep it running? Any ideas? How does the computer interpret the Crank VE Settings? Or are they even relative to it starting for a split second, then dying...?
If I have to give it gas to keep it running when starting it, would it be beneficial to reduce some timing down low, therefore kinda richening it up?
Slowhawk, thats a good idea about the timing, and using just one value. I might try that out this weekend as well...
If I have to give it gas to keep it running when starting it, would it be beneficial to reduce some timing down low, therefore kinda richening it up?
Slowhawk, thats a good idea about the timing, and using just one value. I might try that out this weekend as well...
joel
Originally Posted by binksz06
How much did you back down VE at idle RPM?? Maybe too lean?? FWIW.
joel
joel
I can basically just take my calculated VE numbers, and insert them into the VE table in the appropriate kPa vs RPM slot, and all should be good for VE right?
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Originally Posted by JxxxOxxxE
If I remember right, without being at home and looking at the files, I think I just did the 60%, 70%, 80% thing for the 400, 800, and 1200 RPM columns. I havent manually put in any od my new found VE numbers yet, although they should help right?
I can basically just take my calculated VE numbers, and insert them into the VE table in the appropriate kPa vs RPM slot, and all should be good for VE right?
I can basically just take my calculated VE numbers, and insert them into the VE table in the appropriate kPa vs RPM slot, and all should be good for VE right?
joel
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Originally Posted by jimmyblue
If this is really "lean surge" related then making cold idle richer
(VE or other method) seems the straightest. Is there a "****"
for target cold idle AFR?
(VE or other method) seems the straightest. Is there a "****"
for target cold idle AFR?
joel