Quick MS Questions (Closed Loop and Decel)

1005 Views 8 Replies 3 Participants Last post by Stealth, Oct 9, 2008

Stealth

Discussion Starter · Oct 8, 2008

So overall the car is running good. I have 250 miles on the motor now, very drivable and my AFR's are pretty dang close to ideal without 02 driven correction on.

I just have 2 slight problems

1) Bouncy Idle after ~ 5 mins of driving
- Im presuming what is happening here is after the car starts and idles normally, I drive for a few minutes and it goes into closed loop control. Its bouncing between 2 cells on my VE table. The values were a bit far apart and was a bit lean on the "more vacuum" cell. I adjusted this value closer to the value above it one the table, the AFR is more deserable, and it tightened up the range of the bounce in the idle. I do not want to move this value any more because the AFR is correct. My idle is high ~1500, I can bring that down a bit with the IAC screw.

I guess my question is am I looking at a closed loop settings issue, or a idle RPM issue? It seems like my idle is high and its trying to adjust it lower, then it pops back up to normal.

2) Lean on Decel
- Whenever I let off the gas 100%, foot off the pedal while in gear, the wideband will lean out for a split second. The car stutters ever so slightly and then it pops back to normal. If I toss it in neutral and use the brakes I have no problems, its only when engine braking (decel in gear)

Turn decel enrich off is set to never.

AND now that I think about it these might be related. I never did calibrate TPS after the engine swap. I will try that tommorow morning along with lowering the idle. If anyone has any other suggestions feel free to speak up.

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Trent

· #2 · Oct 8, 2008

what does your vacuum look like at idle?

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Stealth

Discussion Starter · #3 · Oct 8, 2008

20 inHG idle, and 21 on the geared decel.

My VE table goes down to 30 kPa

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Matt Cramer

· #4 · Oct 8, 2008

Could you post a copy of your MSQ and a data log of the problems happening? These are very helpful with tuning issues like this one.

If you're taking a data log to help us out, you can mark where the problem happens by pushing the space bar - this can help a later reader skip right to the issues.

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Stealth

Discussion Starter · #5 · Oct 8, 2008

Yep I can, actually my work schedule has changed, Ill be getting off at 2:30 for the rest of this week I will post it up when I get home today.

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Stealth

Discussion Starter · #6 · Oct 8, 2008 (Edited)

Calibrated the TPS the bouncing idle went away. I still have the lean on decel problem. You can see in this prnt scrn that the duty cycle and pulse width drop to 0 esentially shutting the injectors off.

Also notice the AFR spikes when vacuum increases (let off throttle)

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Matt Cramer

· #7 · Oct 9, 2008

Looks like the overrun fuel cut kicking in; you can turn that off or lower the minimum MAP needed to activate it if you don't want it.

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Stealth

Discussion Starter · #8 · Oct 9, 2008

Ok, I will look into that when I get home from work today.

I appreciate the help :tup:

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Stealth

Discussion Starter · #9 · Oct 9, 2008

I have not made the change, but just looking at the MSQ I can easily tell it is the over run fuel cut. I will make the change and Im sure it will solve my problem. Thanks for the help, I cant beleive I missed that setting :sigh:

Edit - That should also help with all my other lean spikes as well looking at the datalog again. This puppy should be running prime after this change, just 200 more miles and its going on the dyno.

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