rolling idle on decel?

[drhill]

ok, I thought I had a BOV issue but maybe not. Here is the issue, let me know what you guys think:

The car will decelerate normally from cruising speed until the trans disengages and drops the engine to idle speed. Most of the time, the Idle drops a bit too far, IAC/EEC corrects...revs to 2000rpm and it continues rolling up and down until the car comes almost to a stop where it idles normally....or sometimes it stalls during this situation.

From my old 5.0 mustang vortech experience this would be a dashpot setting adjustment, is there anything like this on these cars? I can't imagine this is a BOV issue as the rpm's are very low when the rolling occurs?

Any thoughts/ideas/experiences with this?

Thanks!!

[drhill]

anyone have any ideas on this?

[NavySeabee]

^^^^:bump:

[tbone]

I have the exact same issue.

[Comin' in Hot]

do you have any idle issues in park?

[fastblackmerc]

Clean the MAF, IAC and TB.

Use the correct cleaner for each.

[justbob]

For a hanging idle or a low/stalling idle its the IAC 90% of the time. Cleaning will only help for small doses at a time till its shot. Yes, they do go bad.

This is assuming you haven't changed anything in your tune.


Self proclaimed Builder Of Badassery.

[drhill]

no idle issues in park or at any other time actually. Just the decel issue. My tuner swears its the BOV routing, I just don't have the time or skill to make a pipe and weld a bung where he thinks the BOV should dump into the blower intake tube.

Good point - easy enough clean the maf, tb and iac.

[1stMerc]

How was it driving before the tune, and what did he change?

[drhill]

same...I came in with this issue as something I wanted him to fix...he said I needed to change the BOV/bypass return location so that it blows air towards the blower inlet...he said he could see backwash into the MAF even at idle speeds? (of course on the dyno with huge cooling fans blowing...

[Comin' in Hot]

same...I came in with this issue as something I wanted him to fix...he said I needed to change the BOV/bypass return location so that it blows air towards the blower inlet...he said he could see backwash into the MAF even at idle speeds? (of course on the dyno with huge cooling fans blowing...


I'm sure I have the same setup, but take some pictures and I'll work on a fix. A new BOV is on my list of things to change.

[drhill]

I'm sure I have the same setup, but take some pictures and I'll work on a fix. A new BOV is on my list of things to change.

sweet...I'll take pics! :burnout:

[tbone]

I did all the above and installed a new IAC. No change. Doesn't do it all the time either. Irritating as hell when it does. Car never stalls though and stops bumping up and down around 35 mph.

[drhill]

interesting - mine doesn't do it all of the time...just most of the time. And carries it through to about 10 mph maybe less. If mine stalls, it happens pretty quickly - with in one or two cycles.

[Mike M]

Mine will do that if I do a couple strong pulls down the street, as I let off and slow down I feel it hunting for a few cycles but it hasn't been too much of a problem.

Their is a software dash pot in the PCM that you can modify it's parameters just for this.

[martyo]

If I am understanding correctly, this is not a new issue to your car(s).

I would suggest that it is the tune and likely in the IAC values. It can take some finess to address this but it is fixable assuming that all is well and set up correctly.

[drhill]

I haven't had mine too long but yes, the car had been tuned by someone previously and it did already exist.

[tbone]

Mine will do that if I do a couple strong pulls down the street, as I let off and slow down I feel it hunting for a few cycles but it hasn't been too much of a problem.

Their is a software dash pot in the PCM that you can modify it's parameters just for this.

Can you elaborate on this?

[Mike M]

Yes I can, what exactly do you want to know?

[tbone]

How do I modify the software dash pot?

[Mike M]

How do I modify the software dash pot?

Do you the software to get in to your PCM?

[tbone]

I have an Xcal II with a custom dyno tune and a zack tune on it.

[Mike M]

I have an Xcal II with a custom dyno tune and a zack tune on it.


Nope, you need real software.

You need to be able to change some parameters in the "decay rate" and the "clips/prepositions". These are not idle control parameters, they are parameters to control the transition to idle.

[tbone]

Nope, you need real software.

You need to be able to change some parameters in the "decay rate" and the "clips/prepositions". These are not idle control parameters, they are parameters to control the transition to idle.

I figured I would not be able to do it myself with my xcal. I would imagine my tuner guy could do it though.

The decay rate and clips/prepositions you mentioned should help me approach him on the subject. Thanks.

[RacerX]

I had this problem and changed some dash pot settings. I found the answer to be with CFSO. When you go to closed throttle and drop below a certain rpm, the PCM shuts off the injectors completely. If you have a wideband, you can actually see this, then the tc unlocks and the pcm turns the injectors back on then the converter locks, injectors turn off, convertor unlocks, injectors turn on.... I disabled coasting fuel shut off and the problem went away.

[Seneca]

wow... Good post as my car does this from time to time too. it'll stall once in a while too. thanks for all the input and posting this.

[tbone]

I had this problem and changed some dash pot settings. I found the answer to be with CFSO. When you go to closed throttle and drop below a certain rpm, the PCM shuts off the injectors completely. If you have a wideband, you can actually see this, then the tc unlocks and the pcm turns the injectors back on then the converter locks, injectors turn off, convertor unlocks, injectors turn on.... I disabled coasting fuel shut off and the problem went away.


Yep, this is what my car does with the tc and all.:beer:

Where can I get the software? I assume a laptop and cable is the only hardware I need......

[Mike M]

This is what I bought, Commando



http://www.deltaforcetuning.com/category-s/1.htm

[tbone]

Thanks for the info bro.

[drhill]

I'm sure I have the same setup, but take some pictures and I'll work on a fix. A new BOV is on my list of things to change.

Finally got to some BOV pics: Here's how mine looks. Tuner said have the BOV outlet point directly at the blower inlet if possible(like at the radiator side of the black elbow) or at a very sharp angle pointing upstream towards the blower inlet. PM me and we can discuss the details...
http://i697.photobucket.com/albums/vv340/drhill/Marauderblowerelbow.jpg
http://i697.photobucket.com/albums/vv340/drhill/marauderBOV.jpg