pulsing idle with megasquirt

[rocklizzard91]

hey all, ive got ms2 with a 3.57 board running a single mk2 coil and the dizzy for the crank sensor.

im getting some random pulsing when idling from time to time. i can never get a nice rock solid idle out of the car in the few years ive been tuning it.
any suggestions? its a 16v with cams and a lw flywheel if that matters

its got idle advance set to 28* because that seems to work best for me

[-RalleyTuned-]

Having the stock distributor always makes idle tuning a huge headache. I don't honestly think you will ever have a 100% perfect idle while using it. Add cams to that and it becomes even more difficult!

Usually a hunting idle is due to too much advance at idle. The last 16v I worked on that had a similar configuration idled pretty well, but it was never "rock solid" but it was a race car so it idled a bit high and we never messed with it. It had around 16deg of advance and idled around 13.8-14.2

[rocklizzard91]

Having the stock distributor always makes idle tuning a huge headache. I don't honestly think you will ever have a 100% perfect idle while using it. Add cams to that and it becomes even more difficult!

Usually a hunting idle is due to too much advance at idle. The last 16v I worked on that had a similar configuration idled pretty well, but it was never "rock solid" but it was a race car so it idled a bit high and we never messed with it. It had around 16deg of advance and idled around 13.8-14.2

alright, iw as hoping youd reply you know your stuff
i was hoping it was the dizzy bing the issue. a trigger wheel would be ideal right?
either the aba internal one, or one on the crank pully?

im at 28* and its a little on the lean side. when its really warm itll do pretty decent at 800-900 rpm idling. was just hoping for a little more consistent

[ps2375]

I would suggest bringing the timing at idle speed back closer to 6* BTDC and allowing more air in and adding fuel. You shouldn't need to have that much ign adv at idle. You may need to idle at a higher rpm than stock range due to cams and the LW FW. More due to FW than the cams.

[rocklizzard91]

alright, i need to remember what i have mechanical timing set to then.
how much higher are we talking? like 1k rpm? or higher?

[sdezego]

Are you running Batch, Alternating injection etc? What Size injectors and what Fuel Pressure? Also, are you running Wideband and are you running closed loop 02 at idle and if so what algorithm (Simple or PID)?

All of these things matter tremendously as does the tune.

As mentioned though your timing is way too far advanced. I prefer more around 8-10* on an 8v or 16v, but NO MORE than 12 (unless you have some very insane CAM that requires something odd). If in fact that is your ACTUAL idle advance (have you verified with an adjustable timing light that works proper?) of course. Also, make sure you have consistent bins around the idle regions. Both for VE and Ign. Some used to try to do timing based idle and have diff adv in the first col for instance. I was never into that. Interpolation between bins that are significantly different in idle regions can cause oscillation effects.

I can tell you that I had my G60 with 42# inj running full batch on MS1 (even before the HiRes Code)idling pretty darn well. Now, with MSIII and Alt inj

No reason you shouldn't be able to get your MSII setup darn near rock steady.

[ps2375]

1K at the most, I would think. Before it dropped a valve, we had the 1.8 16V w/ 288* cams on ITB's idling between 900-1000 rpm. And we had a 7-8# FW on it. And timing was around 6*BTDC.

Are you on a stock intake mani?

[Jones84]

I was having this same issue with my 16v for a wile on the same MS you have. All i did to fix it was ad a small in-line fuel filter to the map vac line. It made my idle solid. Much better. I also changed my RPM bins at the bottom end to 800, 1000, 1200. Its seemed to help with the idle tuning from hot to cold. Cold its at about 800rpm hot its about 1100.

[-RalleyTuned-]

a trigger wheel would be ideal right?
either the aba internal one, or one on the crank pully?

im at 28* and its a little on the lean side. when its really warm itll do pretty decent at 800-900 rpm idling. was just hoping for a little more consistent

Having a vr sensor instead of a hall just makes it really easy. All of the tips listed above will help, and it is for sure 28* is about 15 or more deg too much, also running lean with that much advance will cause the issues you are talking about. My main point is it take a lot of tuning when you have the stock hall sender and cams, its not that it is totally impossible, it's just a lot more time consuming. I have never had one that had a dead nuts 100% perfect idle all the time with that setup, whereas my 1.8t on ms2 idled perfect with almost no tuning at all.

Stock 16v idle is 6* and I usually run my ms'd cars around that up towards 10. A small increase in idle speed can help with the cams, and a hair more advance, certainly not 28* though. Idle always likes being a little richer than stoich, I try and shoot for 14.2ish.