Idle Surging.
Apr 23, 2008, 07:22 PM
#49
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i have the same problem.. when i go to stop at a light or something... it will stay above 1k rpm like at 1300 or something around that... then if i rev the engine just a tad in nuetral, it will fall to where it needs to be... i have a catless tbe with a cel fix.. 2 spark plug non foulers. anything to do with it?
Apr 23, 2008, 08:57 PM
#52
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Are your idle maps in the ROM stock? I've found that this symptom can be caused by raising the Desired Idle RPM-Neutral values. Put this one and the Desired Idle RPM-Drive values back to stock and try that if you haven't already.
Apr 24, 2008, 04:27 PM
#54
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If your map is stock, tuning it wouldn't *fix* the problem but may mask it. If you really want to fix the problem, leave the ECU alone and figure out the mechanical culprit.
Apr 24, 2008, 05:16 PM
#55
hey man check your IAC. under the throttle body. my car is currently surging like this sorta.. it goes up to 2k at warmup and wont go down at all and then when i blirp the throttle the rpms kinda stay up ther for a bit and then SLOWLY go down. i KNOW mine's the IAC for sure.. not sure about your problem though. .jsut thought i'd throw that in. good luck and ill be wathcint he thread 
Apr 25, 2008, 09:39 AM
#56
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i figured mine is the IAC too probably form my meth set up. but its weird it comes and goes its not like constant. its really bad right now but i think its a dirty MAF at the moment.
Apr 25, 2008, 10:46 AM
#57
I don't think it's the IAC, at least for me since I don't run meth or anything that would damage it. I have had this probably on and off for a while, too, but never got around to looking into it to resolve it. There could be a number of reasons and everyone that has it could be different, but for me, I think it has to do with the idle map changes, that pd1 mentioned. I think adjusting that in combination with the idle stepper tables can resolve it or cause it.
For me, I get two situations, that may or may not be related. One is the idle surging up and down, when rolling to a stop, for example. Happens more so when the car is warming up. It seems like the idle wants to raise too much, then the ECU corrects and drops too much, then it raises up too much again, etc. Once the car actually stops, the surging/bouncing doesn't happen. It seems to be related to the speed sensor in some way.
The second issue that I have seen is for some reason, after the car warms up, especially on warmer days, when the car is sitting at idle sometimes it will seem to stumble for a split second, at the same time going slightly rich on the wideband and RPMs jumping a bit. Sometimes it may do this a few times in succession, separated by a second or two, but now at idle. It's almost as if someone is gently blipping the throttle. The weird thing is if I let the car do it's thing, eventually, it starts idling very lean, as if it shut off an injector to correct this, and the AFR slowly comes back to normal and it stops. This may be totally unrelated to what I explained above, though, and this can be anything from misfires, to the MAF bouncing around (since mine isn't really secure), etc. I just haven't had anytime to sit down to resolve it yet, but I figured I would add to the discussion.
Eric
For me, I get two situations, that may or may not be related. One is the idle surging up and down, when rolling to a stop, for example. Happens more so when the car is warming up. It seems like the idle wants to raise too much, then the ECU corrects and drops too much, then it raises up too much again, etc. Once the car actually stops, the surging/bouncing doesn't happen. It seems to be related to the speed sensor in some way.
The second issue that I have seen is for some reason, after the car warms up, especially on warmer days, when the car is sitting at idle sometimes it will seem to stumble for a split second, at the same time going slightly rich on the wideband and RPMs jumping a bit. Sometimes it may do this a few times in succession, separated by a second or two, but now at idle. It's almost as if someone is gently blipping the throttle. The weird thing is if I let the car do it's thing, eventually, it starts idling very lean, as if it shut off an injector to correct this, and the AFR slowly comes back to normal and it stops. This may be totally unrelated to what I explained above, though, and this can be anything from misfires, to the MAF bouncing around (since mine isn't really secure), etc. I just haven't had anytime to sit down to resolve it yet, but I figured I would add to the discussion.
Eric
Last edited by l2r99gst; Apr 25, 2008 at 10:49 AM.
Apr 25, 2008, 05:03 PM
#58
I don't think it's the IAC, at least for me since I don't run meth or anything that would damage it. I have had this probably on and off for a while, too, but never got around to looking into it to resolve it. There could be a number of reasons and everyone that has it could be different, but for me, I think it has to do with the idle map changes, that pd1 mentioned. I think adjusting that in combination with the idle stepper tables can resolve it or cause it.
For me, I get two situations, that may or may not be related. One is the idle surging up and down, when rolling to a stop, for example. Happens more so when the car is warming up. It seems like the idle wants to raise too much, then the ECU corrects and drops too much, then it raises up too much again, etc. Once the car actually stops, the surging/bouncing doesn't happen. It seems to be related to the speed sensor in some way.
The second issue that I have seen is for some reason, after the car warms up, especially on warmer days, when the car is sitting at idle sometimes it will seem to stumble for a split second, at the same time going slightly rich on the wideband and RPMs jumping a bit. Sometimes it may do this a few times in succession, separated by a second or two, but now at idle. It's almost as if someone is gently blipping the throttle. The weird thing is if I let the car do it's thing, eventually, it starts idling very lean, as if it shut off an injector to correct this, and the AFR slowly comes back to normal and it stops. This may be totally unrelated to what I explained above, though, and this can be anything from misfires, to the MAF bouncing around (since mine isn't really secure), etc. I just haven't had anytime to sit down to resolve it yet, but I figured I would add to the discussion.
Eric
For me, I get two situations, that may or may not be related. One is the idle surging up and down, when rolling to a stop, for example. Happens more so when the car is warming up. It seems like the idle wants to raise too much, then the ECU corrects and drops too much, then it raises up too much again, etc. Once the car actually stops, the surging/bouncing doesn't happen. It seems to be related to the speed sensor in some way.
The second issue that I have seen is for some reason, after the car warms up, especially on warmer days, when the car is sitting at idle sometimes it will seem to stumble for a split second, at the same time going slightly rich on the wideband and RPMs jumping a bit. Sometimes it may do this a few times in succession, separated by a second or two, but now at idle. It's almost as if someone is gently blipping the throttle. The weird thing is if I let the car do it's thing, eventually, it starts idling very lean, as if it shut off an injector to correct this, and the AFR slowly comes back to normal and it stops. This may be totally unrelated to what I explained above, though, and this can be anything from misfires, to the MAF bouncing around (since mine isn't really secure), etc. I just haven't had anytime to sit down to resolve it yet, but I figured I would add to the discussion.
Eric
This is what mine does also. It gets worse the colder it gets outside.
Apr 26, 2008, 12:36 PM
#59
Have you checked the:
vac lines (unmetered air will cause run on)?
power steering pump pressure switch ground?
IAC by removing servo for inspecting and disconnecting connector?
bad off idle ignition map will cause run-on too.
Since your running rich while this is happening try this: coast down a hill in suitable gear while air pumping engine until injector cut (0 IPW), if your not getting high O2 (< 20%) then injector is leaking.
vac lines (unmetered air will cause run on)?
power steering pump pressure switch ground?
IAC by removing servo for inspecting and disconnecting connector?
bad off idle ignition map will cause run-on too.
Since your running rich while this is happening try this: coast down a hill in suitable gear while air pumping engine until injector cut (0 IPW), if your not getting high O2 (< 20%) then injector is leaking.
Feb 9, 2009, 10:59 AM
#60
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check your "IAC" which its correct nomenclature is Idle Speed Control Vavle "ISC", all you need is a multimeter and check for 33-66k ohlms between pins 1 and 2, 2 and 3, 4 and 5, 5 and 6, pin 1 is to the top right as it sits in the car, if you get between those readings your ISC connector and unenergized electronic inside are good, then next step is to take the ISC off and visually inspect the plunger and to see if there is any fluid in the servo housing. the ISC servo doesn't have that great of sealing on it so water and meth or even oil brought up from the LIC pipe and IC can get in side and damage it, i know this cause a buddy of mine fried his with meth, damn thing took me 2 days to narrow down to it. hope this helps, good luck bro