Surging When coming to a stop- 10 MPH only

[BowlingSS]

I have a 2001 running COS5. Everything seems to be dialed in except one item. Most of the time after the engine is hot, when I am slowing down at 10 MPH I get a surge to 1200 or so and then back down to 850 idle.
My RAFIG is real close +- .2. I have changed the RAFIG to plus side and minus side. I have tried to increase my Throttle Cracker Table with no help. I have also tried changeing my Throttle Follower Table. Why I think it it is the Cracker table is I have it set to come on at 10 MPH.

I did notice yesterday with the AC on it was not as bad.

What does everyone think I should try next? It is getting warmer now so my tune could change since I am running SD without a MAF installed.

Thanks,
Bill:master: :cheers:

[SSpdDmon]

I'd say it's the throttle cracker. What RPM are you at when this happens. If you look them up in the table, what value is there? What speed does it enable/disable?

[TAQuickness]

+1 for the throttle cracker. In my case, it turned out I had way too much air for parking lot speeds. I believe my values ended up in the .5 g/s range all said and done.

[BowlingSS]

I'd say it's the throttle cracker. What RPM are you at when this happens. If you look them up in the table, what value is there? What speed does it enable/disable?

The RPM goes to about a 1000 and then when it hits 10 MPH it surges to 1200 or so. The enable speed (B4311) is 10 KMH and (B4312) 9 KMH Deactivate. I just noticed they are in KMH instead of MPH. The table (B4309)shows 0 right now at 1000RPM. It shows MPH not KWH. I need to change the values to MPH. I am going to change this to .3 to see if that is enough.

Thanks for the help.
Bill:master:

[SSpdDmon]

The RPM goes to about a 1000 and then when it hits 10 MPH it surges to 1200 or so. The enable speed (B4311) is 10 KMH and (B4312) 9 KMH Deactivate. I just noticed they are in KMH instead of MPH. The table (B4309)shows 0 right now at 1000RPM. It shows MPH not KWH. I need to change the values to MPH. I am going to change this to .3 to see if that is enough.

Thanks for the help.
Bill:master:

Well, once you figure out what RPM/MPH it's at, that's half the battle. The rest is just making the right changes to fix it. :)

IIRC, I set speeds and temps to imperial. Most everything else is metric. To change your settings, just click on this:

[BowlingSS]

It looks like .3 was not enough. I set it to .5 and will try it tomorrow.

Bill
:cheers:

[Rhino79]

I have found good results in my experiences with 0'ing out the TC below 15 mph or so depending on vehicle.

[BowlingSS]

I have found good results in my experiences with 0'ing out the TC below 15 mph or so depending on vehicle.

What tables did you 0 out?

Bill
:cheers:

[Rhino79]

I actually just changed the enable speed to 15 disable at 13. You can also 0 the TC airflow table in the corresponding rpm range and speed range.

[RevGTO]

Forgive me for suggesting the obvious, but are you sure it's not your tranny downshifting to first at that point and thus giving the rpms a bump?

[BowlingSS]

I actually just changed the enable speed to 15 disable at 13. You can also 0 the TC airflow table in the corresponding rpm range and speed range.

I changed the enable to 15 and disabled to 13. I also 0 the TC table. Still have the surge problem.

Bill
:cheers:

[oztracktuning]

Its likely lean as well

[BowlingSS]

Its likely lean as well
I will check the VE Table tomorrow in that area.

Thanks,
Bill
:cheers:

[Rhino79]

What kind of timing are you seeing/commanding in that area?

[808ws6]

I actually just changed the enable speed to 15 disable at 13. You can also 0 the TC airflow table in the corresponding rpm range and speed range.


Hey Rhino79!

Thanks for that suggestion. It fixed the surge I was experiencing when I was coming to a stop especially with the a/c on.

I was experiencing and RPM surge that rose to 1500 rpm briefly then dropped to 1200 rpm for about 5 sec's then dropped to my desired 950 rpm idle.

Now it goes back to desired idle speed before I come to a stop, WAY better!

Thanks!

Gil

[BowlingSS]

Forgive me for suggesting the obvious, but are you sure it's not your tranny downshifting to first at that point and thus giving the rpms a bump?

This could be a problem because the trany does downshift at 12mph but I have never noticed this before or at least not this much. Why would it surge that much on the downshift? What can I change to correct this?

Bill
:cheers:

[BowlingSS]

What kind of timing are you seeing/commanding in that area?

About 26. Should I try to move it up some?

Bill:master:

[BowlingSS]

Its likely lean as well

The TPS VE Table looks great at those RPM's. My BEN's are 0.99 and 1.00.

Bill
:master:

[Rhino79]

Hey Rhino79!

Thanks for that suggestion. It fixed the surge I was experiencing when I was coming to a stop especially with the a/c on.

I was experiencing and RPM surge that rose to 1500 rpm briefly then dropped to 1200 rpm for about 5 sec's then dropped to my desired 950 rpm idle.

Now it goes back to desired idle speed before I come to a stop, WAY better!

Thanks!

Gil

Awesome, now if we can just figure out BowlingSS's issue I'd feel even better!

[jfpilla]

Did this get worse when the weather warmed? If you see engine temps above 85*C you might try lowering B4307 at 92*C. It might need raising then at 80*C.

[RevGTO]

This could be a problem because the trany does downshift at 12mph but I have never noticed this before or at least not this much. Why would it surge that much on the downshift? What can I change to correct this? Bill :cheers:I mentioned it because I noticed it on my car when I was struggling with hanging idle issues. I became over-sensitive to what my idle was doing, and noticed that it typically would bump up around 10mph as I was coasting to a stop. Then I figured out that that was just the rpms bumping up as the A4 shifted into first at that point - higher revs as the result of lower gearing and not a problem.

[BowlingSS]

I mentioned it because I noticed it on my car when I was struggling with hanging idle issues. I became over-sensitive to what my idle was doing, and noticed that it typically would bump up around 10mph as I was coasting to a stop. Then I figured out that that was just the rpms bumping up as the A4 shifted into first at that point - higher revs as the result of lower gearing and not a problem.

Is there anyway to smooth it out a little? Maybe I just have to live with it.

Bill
:cheers:

[jfpilla]

Given all the rest of the transition tune is right, you can try lowering B4309, a lot, in the rpm and mph areas where this happens. If you can get the car to essentially idle where the trans hangup occurs during the downshift it should go away. You may then need to add a little air at the point where you almost come to a stop. Sort of like a bump stop. I lowered B4311 to 2 and 4312 to 1. It's the oppisite from all I've read that others do, but it works great for me.