(Video) What does this surge/stall issue look like to you?
03-16-2013, 09:27 AM
#1
(Video) What does this surge/stall issue look like to you? My car has been like this ever since the build last summer. Trying to to get out of my uphill driveway it will surge and most of the time stall.
In reverse its a total nightmare. Any time I give the car throttle in reverse it is just about guaranteed to surge then stall.
Usually it is very rare for the car to act up on the street coming to a stop but today just sitting in traffic I noticed there was a slight non stop surge of maybe 100rpm or so.
I took a vid of what happens when the car is just at idle, in park, and I rev the engine. Watch the 2nd time I rev, the rpms just surge up and down almost stalling untill it finds a steady idle. Then, watch the 6th time I rev, it does the same thing but this time stalls.
What kind of an issue does this look like?
In reverse its a total nightmare. Any time I give the car throttle in reverse it is just about guaranteed to surge then stall.
Usually it is very rare for the car to act up on the street coming to a stop but today just sitting in traffic I noticed there was a slight non stop surge of maybe 100rpm or so.
I took a vid of what happens when the car is just at idle, in park, and I rev the engine. Watch the 2nd time I rev, the rpms just surge up and down almost stalling untill it finds a steady idle. Then, watch the 6th time I rev, it does the same thing but this time stalls.
What kind of an issue does this look like?
03-16-2013, 10:09 AM
#2
The surging and stalling is the finer part of tuning provided there is no mechanical issue. It's desired airflow, maybe idle spark control delay, throttle cracker, and or throttle follower, idle overspeed and underspeed, base spark in gear, base spark in park/neutral, etc.
You have to find someone that knows something more than wide open throttle dyno-theiving.
I know I have not specifically answered your question, but to do that one would need connect to your PCM with EFI Live or HPT and log what's going on. If you can't find a local tuning artist, there are people that can do this stuff pretty darn effectively with remote or mail order tuning.
Good luck with it.
You have to find someone that knows something more than wide open throttle dyno-theiving.
I know I have not specifically answered your question, but to do that one would need connect to your PCM with EFI Live or HPT and log what's going on. If you can't find a local tuning artist, there are people that can do this stuff pretty darn effectively with remote or mail order tuning.
Good luck with it.
03-17-2013, 01:41 AM
#7
TECH Fanatic
I vote vacum leak, or thats where Id start. Get a spray bottle, and find it! Good luck. Makesure all your vacum lines are going to the right places! PVC, EGR, so on and so forth!
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03-18-2013, 09:02 AM
#10
Just needs some tweaks on the throttle follower in the higher tps settings, A little less timing probably in that area by a few deg, and a correction to make the iac correction less aggressive when it is down in the lower rpms to get rid of the massive overshoot. Should take Don a single flash to fix that..
03-18-2013, 01:10 PM
#11
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In my book, the number one cause of unstable idle
is an excessively rich idle mixture.
Especially on cars with a high-overlap cam, but even
on mine (224 on 116), there is a fair difference from
what idles best to what ways stoich on the wideband.
Shot-through air biases the indication lean, so if you
follow the paste-histo semi-auto-magical method you
will stop at a point where the numbers are good and
the result is crappy (rich in the cylinder, stoich in the
pipe).
The same issue pertains to the narrowbands in closed
loop.
My recommendation is to play with the scan tool's
bidirectional controls, locking down everything but
commanded AFR in open loop idle and find the happy
place, indicated by minimum MAP to idle at your
set RPM (bump IAC manually, so that loop can't be
bugging). Then you record the indicated wideband
AFR and the narrowband average voltages, use
the WB AFR as your target instead of textbook
stoich for hand-fitting (or hack your own Excel)
idle and below and use the narrowband number
in your O2 mV vs airflow mode table so the closed
loop trims won't undo your work, but seek the
same point.
I do think I've messed some with the idle RPM
loop's PID values as well, in the end, but it's the
mixture that's been the big deal on all the cars
and trucks I've touched.
I do recommend setting the idle air mass numbers
above "what it needs" so that on every drop-to-
idle, you start with more and pull to less instead
of potentially dropping to not-enough, and thus
to a really hard to tune / observe section of the
fuel and timing maps. The 400RPM column can be
no more than a guess. But it's worth some rounds
of guessing in itself, because below 800RPM it's
interpolated into the mix.
is an excessively rich idle mixture.
Especially on cars with a high-overlap cam, but even
on mine (224 on 116), there is a fair difference from
what idles best to what ways stoich on the wideband.
Shot-through air biases the indication lean, so if you
follow the paste-histo semi-auto-magical method you
will stop at a point where the numbers are good and
the result is crappy (rich in the cylinder, stoich in the
pipe).
The same issue pertains to the narrowbands in closed
loop.
My recommendation is to play with the scan tool's
bidirectional controls, locking down everything but
commanded AFR in open loop idle and find the happy
place, indicated by minimum MAP to idle at your
set RPM (bump IAC manually, so that loop can't be
bugging). Then you record the indicated wideband
AFR and the narrowband average voltages, use
the WB AFR as your target instead of textbook
stoich for hand-fitting (or hack your own Excel)
idle and below and use the narrowband number
in your O2 mV vs airflow mode table so the closed
loop trims won't undo your work, but seek the
same point.
I do think I've messed some with the idle RPM
loop's PID values as well, in the end, but it's the
mixture that's been the big deal on all the cars
and trucks I've touched.
I do recommend setting the idle air mass numbers
above "what it needs" so that on every drop-to-
idle, you start with more and pull to less instead
of potentially dropping to not-enough, and thus
to a really hard to tune / observe section of the
fuel and timing maps. The 400RPM column can be
no more than a guess. But it's worth some rounds
of guessing in itself, because below 800RPM it's
interpolated into the mix.
03-19-2013, 11:10 AM
#14
Hmm ok. TB blade is set the same from the install last summer. Car still acts the same as if did last summer. So the blade must have always been open too far or this fast 92 must have always had a vacuum leak. Or maybe both and the extra air through the TB blade was used to tune around a vacuum leak from the fast 92?
03-19-2013, 03:54 PM
#15
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When the motor wants "less than zero" and the IAC
is bottomed, the RPM control loop gets "wound up"
and that can be another source of instability, when
you manage to wake it up momentarily.
The 92mm intakes seem to give a lot of idle grief.
Might want to check the IAC bore and anywhere
you can't pass a 3/8" drill bit, relieve it. Being sure
not to mung the plunger seating circle of course.
is bottomed, the RPM control loop gets "wound up"
and that can be another source of instability, when
you manage to wake it up momentarily.
The 92mm intakes seem to give a lot of idle grief.
Might want to check the IAC bore and anywhere
you can't pass a 3/8" drill bit, relieve it. Being sure
not to mung the plunger seating circle of course.
03-19-2013, 10:18 PM
#16
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Hmm ok. TB blade is set the same from the install last summer. Car still acts the same as if did last summer. So the blade must have always been open too far or this fast 92 must have always had a vacuum leak. Or maybe both and the extra air through the TB blade was used to tune around a vacuum leak from the fast 92?
03-19-2013, 10:48 PM
#17
Im really wondering about the IAC counts showing up as 0 on my gauge. I think I will try closing the TB blade again just to see if it starts showing any IAC counts.
03-21-2013, 04:37 PM
#19
Believe me all follower table's, crackers,timing ect have been adjusted. Would be fine then turn to crap. I'm pointing to a vacuum leak too which I'd put towards the FAST being pourus.
Of course the OP can always bring the car back for us to go over again and start from scratch. I just heard about this yesterday, was under the impression it was fine last summer. LOL
Of course the OP can always bring the car back for us to go over again and start from scratch. I just heard about this yesterday, was under the impression it was fine last summer. LOL
03-21-2013, 05:27 PM
#20
Believe me all follower table's, crackers,timing ect have been adjusted. Would be fine then turn to crap. I'm pointing to a vacuum leak too which I'd put towards the FAST being pourus.
Of course the OP can always bring the car back for us to go over again and start from scratch. I just heard about this yesterday, was under the impression it was fine last summer. LOL
Of course the OP can always bring the car back for us to go over again and start from scratch. I just heard about this yesterday, was under the impression it was fine last summer. LOL
Don whatever was doing this with the car after the build its still there. Its intermittent. I know when I brought it back the 2nd time you couldnt seem to catch what I said it was doing but in the vid is exactly what happens when its being reved, trying to get it out of my uphill driveway, in reverse, and very occasionaly on the street stopping. Other than that, the car is great. Like I said im just trying to trouble shoot it and learn a few things along the way. Its probably like you said...the leaky FAST intakes.
Once again im not saying your tune is bad. Just trying to work out the intermittent bugs that I know have been there since the build