DTC Map 33
#21
05-05-2017, 09:35 PM
IAC motor should close off as the system hands over the RPM control to the throttle plate. You should see the IAC count drop off as the RPMs goes up. At least that is the way the older system I worked on in the 80's worked.
The voltage drop is a symptom of the low RPMs. Once you drop below 600 RPM the alternator is not turning fast enough to make power anymore.
Timing advance table will drop timing advance very quickly at low RPMs in an attempt to keep it from stalling.
It will be tuff to get a good idle with a stock one Bar MAP sensor. Even a stock 2 bar sensor from a super charged GM car would be a lot more accurate but I don't know if you PCM would support and it would need programmed for it.
Is there any chance the IAC is bad/slow or dirty? If an IAC start moving slow you get the up and down surge in RPMs. It is also known as a lazy IAC.
The voltage drop is a symptom of the low RPMs. Once you drop below 600 RPM the alternator is not turning fast enough to make power anymore.
Timing advance table will drop timing advance very quickly at low RPMs in an attempt to keep it from stalling.
It will be tuff to get a good idle with a stock one Bar MAP sensor. Even a stock 2 bar sensor from a super charged GM car would be a lot more accurate but I don't know if you PCM would support and it would need programmed for it.
Is there any chance the IAC is bad/slow or dirty? If an IAC start moving slow you get the up and down surge in RPMs. It is also known as a lazy IAC.
#23
05-06-2017, 12:10 PM
Join Date: Mar 2009
Location: Tokeland, Washington
Posts: 21,645
did you set the new iac? need to pull the pintle so its in a closed position all the time then this 4th Gen LT1 F-body Tech Articles
Last edited by craby; 05-06-2017 at 09:14 PM. Reason: because i like fishing the pinicle
#24
05-06-2017, 12:17 PM
Join Date: Mar 2009
Location: Tokeland, Washington
Posts: 21,645
also be a good idea to reset the idle base setting. actually if your resetting the iac just do this first, while the pintle is in the closed position unplug the iac and start the engine. set your idle, stock is pretty low, 600 i think. i set mine at 800. once you get the minimum/base idle then finish setting the iac.
Last edited by craby; 05-06-2017 at 09:13 PM. Reason: garydoug said so
#27
05-06-2017, 10:56 PM
Ok so I cracked the throttle blades and adjusted tps to .66v. It seems to run a little better. Is anybody experienced in TunerPro RT? I still think my warm idle needs to come up and maybe fine tune some other things like spark advance and VE.
#28
05-07-2017, 12:59 PM
I understand the desire to want to fix this tune issue yourself but you are talking adjusting the tune on a supercharged car. If you mess with a timing map or fuel map and you make changes that effect something besides idle you can wipe out your pistons pretty quickly. Any tune adjustment should be done by someone not asking for help from a forum. Then a final dyno pull to verify everything is working as it should be.
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