# VR6 12v Rough Idle



## acee_dub (Jun 12, 2008)

*VR6 12v Rough Idle MegaSquirt*

Hi, I have my 12v VR6 set up with MS2v3 and it seems to be all good throughout the rpm range (i've slowly taken it up to 3000) if i rev it with the ve auto correct running and making corrections (the auto tune function of TunerStudio) but when I am entirely off throttle and it is idle, the rpms range in 0-650~ almost stalling out the engine, the autotune function seems to have made its corrections to the fuel map and it is still very rough on idle. What are some things I should be looking at to correct this? Another thing which may be related to this is that it is unable to start on a cold motor, I have to heat it on stock ECU in order to get it to start up and run. (It will just crank fast and not catch)


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## Prof315 (Jan 5, 2009)

Sounds like your cranking pulse is wrong. Can you post a copy of your msq or send me a copy? I'd be happy to take a look at it for you.


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## acee_dub (Jun 12, 2008)

Here is the URL with my current.msq which I pulled from the projects directory
http://matrix.senecac.on.ca/~ystasiv/pub/index.php?path=standalone_efi/current/


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## acee_dub (Jun 12, 2008)

bamp  adjusting to the correct crank pulse seems quite complicated


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## bomberbob (Sep 19, 2004)

OBD2? Throttle body doesn't have any kind of adjusting screw for idle. The OEM ECU will use that little electric motor on the side to crack it open a bit to get your idle up. I haven't megasquirted my VR yet, I think if I do I will go to a OBD1 throttle body. Maybe one of the experts can tell you how to make that OBD2 TB work, but I don't know how.
The reason I know is that the TB I have now is busted, that feature doesn't work and so when its cold it will not idle. Have to keep my foot on the gas to warm it up, then it idles around 500 RPM. Thats with the stock ECU.


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## acee_dub (Jun 12, 2008)

Yes it is an OBD2 TB. The car will not cold start and if warm it up with OEM ecu then swap to megasquirt it will run smooth with at minimum about 15% throttle. 

Don't know if this affects it but I have the coolant hoses which used to go to the TB looped off (No longer going to TB)


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## Prof315 (Jan 5, 2009)

acee_dub said:


> Here is the URL with my current.msq which I pulled from the projects directory
> http://matrix.senecac.on.ca/~ystasiv/pub/index.php?path=standalone_efi/current/


I haven't forgotten about looking at this. I had trouble getting the link to work for some reason but finally got it . I'll look tonight after work.

Concerning the OBD2 throttlebody with built in IAC....... I got the ABA version to work in open loop by wiring pins 1 and 2 BACKWARDS and running things inverted in MS. Closed loop seems out of the question as the relationship of DC% to rpm is not linear at all.


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## acee_dub (Jun 12, 2008)

Sweet :laugh:


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## Prof315 (Jan 5, 2009)

Ok I got a look at things and there are 2 issues I noticed immediately.

1: The idle valve frequency is too low. you are set at ~60hz and need to be at least 200hz 

2: You never turn off your warm up enrichment. The final setting ( highest temp) must be set to 100%.

Also you might want to play with the timing at idle, especially while getting things up and running. A little more might help say 10-12 deg

Finally you have the accel enrichment threshold set kind of low. VW TP sensors tend to be a little noisy. 80-90%/sec will keep you from false triggering.


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## acee_dub (Jun 12, 2008)

I have changed the idle valve frequency to 200~hz and it still dies out on idle (dips to almost if not 0 rpm and then back up to 600), should I continue to raise the frequency? How high should I go?


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## need_a_VR6 (May 19, 1999)

Now that you are at 200hz try varing the duty. On ms3 you can try frequencies upwards of 1khz.


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## acee_dub (Jun 12, 2008)

The idle control is set to PWM Warmup
I have Increased the Accel Enrichment to 80%/sec

Warmup Enrichment:
starts at -40.0C Coolant / 180% WUE
ends at 62.8C Coolant / 100% WUE 

Idle still rough, bouncing between 0-600rpm


Where can I variate the duty? Is it one of these:










How would I find the right setting for the duty? Do I lower the minimal temps until it will start and idle while cold?


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## need_a_VR6 (May 19, 1999)

The one on the left. With the car at a warm idle, vary the duty to see what kind of response you get.


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## acee_dub (Jun 12, 2008)

Varying the duty table did not change idle... it was out of range when I first looked at it (The car was warmed up a bit with the motronic ecu, putting coolant temps at ~60C / ~140F) I changed the table to fit the temps while adding throttle so that the car did not stall out, burned the table and let off throttle to re-test idle. There was no change.. it continued dropping to 0rpm and bumping up again to 500-600~ 

Did I have to power cycle for these values to actually be used or was burning them sufficient?

What else can it be if not the PWM Idle duty cycle? This looks like the last thing stopping me from getting it on the road, while on the throttle keeping it from stalling out, it runs smoother than with the motronic ECU and air fuel ratios are looking good.


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## need_a_VR6 (May 19, 1999)

I would try what Professor Jeff said and flip the wires and invert the output to see if there is a change. Also verify you have a flyback diode installed.


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## acee_dub (Jun 12, 2008)

I have the flyback diode installed, I will try to reverse the wires on my harness. It would be these TPS pins correct?

Motronic T68______MS DB37
41----------------------26--------TPS+
40----------------------22--------TPS

It may be this because I noticed on my TPS calibration the signal is inverted. (Closed throttle ADC count 864, Full throttle ADC count 149).


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## need_a_VR6 (May 19, 1999)

Not the tps wires, the pwm idle valve wires. Its fine to have "backward" tps in ms2 and later.


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## acee_dub (Jun 12, 2008)

Initially my harness was set up as follows:
FIDLE (GRN) MS pin/30 T68 pin/53
12VCD (RED) MS pin/28 T68 pin/23

I have inverted these (switched fidle with 12vcd on the motronic connector) to no change at all, everything is as before, I will look into the flyback diode more thoroughly perhaps there is a mistake there..

Edit:

Here is my Tip122 Fidle mod... the tip122 is on a mica insulator so it is not shorting, the wiring is set up as per manual diagram... Could there be a dead component in the fidle mod?


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## need_a_VR6 (May 19, 1999)

Exactly where does the banded end of the diode land?


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## acee_dub (Jun 12, 2008)

it goes to S12, I noted the manual says it should go to "S12C" but the diagram shows it going to where on my board, is "S12"










Got some readings off the board, orientation of pins as per picture above, not sure if this helps:
Banded side of diode (IN4001): 11.24v (rpm 0) / 11.02v (rpm 3000)
Middle Pin of Tip122: 2.10v (rpm 0) / 1.93v (rpm 3000) 
Right Pin of Tip122: 0v (rpm 0) / 0v (rpm 3000) (r39 reads 0v also)
Left Pin of Tip122: 0.26v (rpm 0) / 0.26v (rpm 3000)


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## acee_dub (Jun 12, 2008)

Here is a datalog, turns out it does idle although just barely (hits 0rpm).. 

I brought it down off throttle slowly and fully let off, the rpm begins to fluctuate and bounce, but it does not stall.

MSLog
MSQ


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## acee_dub (Jun 12, 2008)

Played with idle valve frequency, tried everything from 100-250hz~ no changes 

anybody  halp


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## need_a_VR6 (May 19, 1999)

Take the intake boot off and look at the tb. Key on, vary frequency. Does it move?


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## acee_dub (Jun 12, 2008)

No it does not move... is there a way to test the TB by putting 12v to one of the pins on it or something?


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## need_a_VR6 (May 19, 1999)

Yes 12v/ground across 1/2 should induce motion.


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## acee_dub (Jun 12, 2008)

12v/gnd to pins 1/2 on the TB made the tb move a little, I assume this indicates that it is functional. Would the other end be something with the idle circuit on my MS board? Are there any ways of testing it without connecting to the car?


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## need_a_VR6 (May 19, 1999)

You can check the idle with a stim.


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## acee_dub (Jun 12, 2008)

I have a jimstim and it seems to idle just fine with it hooked up, does that eliminate the possibility of errors in idle circuit? only thing is the harness then


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## need_a_VR6 (May 19, 1999)

acee_dub said:


> I have a jimstim and it seems to idle just fine with it hooked up, does that eliminate the possibility of errors in idle circuit? only thing is the harness then


 The thing to check there is vary the coolant temp and see if the FIDLE led follows it (bright/dim) with vary duty cycle. You might need to change the PWM warmup parameters to get a big enough swing to see it.


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## acee_dub (Jun 12, 2008)

On the JimStim, after setting up a coarse curve on the idle pwm duty table, I can see the FIDL LED vary in glowing intensity when turning the coolant pot, is this normal? (It does not turn off even if RPM is at 0) 

If this is a sign that my FIDLE is operational, and the TB is ok, it must be the harness wiring of MS pin 30 ? Maybe wired to the wrong pin on the bosch connector


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## need_a_VR6 (May 19, 1999)

Yep sounds like the circuit works.


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## Prof315 (Jan 5, 2009)

Actually provided you have the polarity correct (12V to pin 1 Gnd to pin 2) the throttle blade should move a good bit. If you do this on a running engine it will generally run at about 3500-4500 rpms.


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## acee_dub (Jun 12, 2008)

My TB only flinched, and remained at 99% closed position when a 12v was applied to pin 1 and gnd to pin 2... It idles ok on factory bosch ecu, I have also found an error in my harness wiring and corrected it (fidle was on bosch pin 23 and 12vcd was on pin 53, so i switched them around) did not do a test afterwards but i assume good results will come of this


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