Stalling when braking

[SNKEBIT]

Working on an '01 w/ Roe s/c, SVS headers, no cats, water/****, and have a stalling problem when braking hard. Starts right back up and idles fine. Just seems when you let off accelerator it drops way below idle and "catches" itself, going back up to idle where it should. Happens more often than not. Is this a problem w/ the I.A.C. valve? Can I program more fuel in to keep it from going below idle spec.? T.P.S. crappin'out?
Thanks for any insight,
Mitch

 

[LETHAL GTS]

Almost sounds like the TPS.
Happy anniversary you old fart! How did the party go?

 

[Rollin4]

Check throttle bodies and IAC for carbon build up, clean if needed, and see if that cures the problem.

 

[SNKEBIT]

Almost sounds like the TPS.
Happy anniversary you old fart! How did the party go?

What happens in Wisc. stays in Wisc.

 

[Schulmann]

100% same issue here ...


My problem is PCM related. Its idle is set to 710rpm and the dealers can't reprogram it. With a 2000 PCM this problem disappears.

To reduce the issue you can adjust your throttle body.
There are small screws on each side. Adjust the throttle opening so that they will stay open a little. The idle motor is not enough fast to open when you close suddenly the throttle.

You can also play with the throttle body sensor (by removing the small brass pins) but it will not help much.

What is the year of your PCM ?

if you find a better solution please tell me.

 

[SNKEBIT]

Have a 98 pcm in the car.
I will try the throttle adjustment.
Car has always idled slow.

 

[Compensating]

SNKEBIT!!!

 

[Compensating]

SNKEBIT!!!

Your going to think I'm crazy but I think your problem is more basic than you think..

I had this exact same problem for a week... tried everything...

Check your battery.. turns out mine was going bad and it couldn't keep up with the ignition when falling from higher rpm's to idle... just like you said "it catches itself"..

my vote is for a dying battery....

 

[SNKEBIT]

It's got a brand new battery from Dodge in it. Allthough, that doesn't mean the battery is good...

 

[JPL]

I had a stalling problem when I replaced my battery, I was told to disconnect the battery, wait a minute, re-connect the battery, start the car and immediately hold it at 2000 rpm’s, and slowly lift your foot off the gas lowering the rpm’s until your foot is off the gas, this has something to do with the computer relearning where to bottom out and idle, never had a problem since. It’s a quick process, might be worth a shot. Hope this will help you.

 

[Steve 00RT/10]

I am currently having a similar problem with our newly installed Roe SC car. I originally thought the IAC was bad, but replaced the battery instead on advice from JD---At 55,000 miles and over 6 years old....it was due. (the old one still load tests OK) That fixed the problem temporarily. My problem is slightly different in that I have set 3 PO153 codes and 1 PO174 code over 2400 miles. There's 100 track miles in there as well---the car ran great! The symptoms seem exactly the same though....wanting to stall when decelerating to a stop....going low and sometimes stalling, sometimes it will come back on it's own. A slight throttle blip coming to a stop and she's idling normally. Resetting the computer fixes the problem until a light sets again. I erased all the lights with my little OBDII reader/eraser, but I guess that won't reset the adaptives.

I have replaced the left front O2 sensor with no luck. Sean thinks it's in the adaptives and that the reason is a bad voltage signal to the PCM from the left side. He told me to add 20ms to 1,3,5,7,9 and try it again. If adding fuel like this twice does fix it, i'm going to buy an OEM O2 sensor for the left (I bought Bosch for the replacements).

You could try disconnecting all 3 PCM plugs to reset the adaptives. Then show the TPS full throttle voltage and see what happens.

Steve

 

[Schulmann]

I have had this issue for 2 years ...
PCM issue. Dealer can't reprogram the idle speed.

You reduce the problem you have to adjust the throttle such a way that it stays open just a little. It will not encrease the idle speed but will help to avoid stalling.

 

[KenH]

I have had the same issue with my '01 as well. The problem seems to come and go. I tried removing the fuel cut on the VEC2 under high vacuum conditions and that did not seem to help. I tried two different VEC2s. I also had the problem with my original '01 PCM and the '96 PCM that I am running now. Per Schulmann's comment about keeping the throttle bodies open slightly helping the problem, it might be more of a lack of air issue than a lack of fuel or spark. Perhaps the spinning SC creates a big momentary vacuum against the suddenlty closed throttle plates which the IAC can't compensate for starving the engine for air.

 

[SNKEBIT]

I'm starting to lean towards the s/c creating a vacuum w/ the throttle plates close and making the engine starve for air. I have a mini air filter on the I.A.C., would a bigger filter help?

 

[Schulmann]

Air filter doesn't matter.
Really, there are 4 problems:
- "Sudden" vacuum
- low idle speed
- slow IAC motor
- A PCM from the stone age

Compensate with the screws on the trhottle body.
Don't worry, the PCM will hold the idle speed stable. At least it does this.

You can also play with the TPS but it is risky => stupid PCM will advance the ignition 20deg even if the engin is reving 720rpm.