Problems....tip in stumble, and dies

[2 QK 4 U]

Ok, The car idles fine. When I blip the throttle it stumbles then picks up. When I'm driving it and I come to a stop it dies. It didn't do this before I pulled the motor and rebuilt most of it. I did have the cam sensor out though.

I have commander chip
57# inj
LT1 w/trans
the normal bolt on mods.

 

[Ttype83]

What are your IAC and TPS settings?
With mine, it will tip in stumble if I set the IAC to 18-30, but the idle is smooth. I have it set as close to 10 as I could get and it idles a little rough but no tip in.

 

[2 QK 4 U]

What are your IAC and TPS settings?
With mine, it will tip in stumble if I set the IAC to 18-30, but the idle is smooth. I have it set as close to 10 as I could get and it idles a little rough but no tip in.

At Idle the IACs are 49, and TPS is .46

 

[TurboDave]

At Idle the IACs are 49, and TPS is .46

At idle, you should prefer to have the IAC's closer to around 20-30 while in gear, and lower in park/neutral. While adjusting the values make sure to readjust your tps setting also. Adjusting the IAC will take the TPS out of tolerance. Best TPS setting should be .40-.44

.46 is just on the ragged edge of being at the upper limit of "idle values" as recognized by the ECM.

 

[2 QK 4 U]

Thanks Turbo Dave. I can't remember how to adj the IAC, it's been a long time....

I'm using DS to see these values. I'll probably need a buddy to use his eyes. My interface cable won't reach outside.

 

[TurboDave]

Thanks Turbo Dave. I can't remember how to adj the IAC, it's been a long time....

I'm using DS to see these values. I'll probably need a buddy to use his eyes. My interface cable won't reach outside.

With the engine idling in park/neutral, just start tweaking/turning on the throttle blade screw (minimum air bleed adjustment). Turn it in small incraments (1/4 turn at a time), and watch the IAC numbers, they should change a little as the car compensates for turning the screw.

Turning the screw CW will open the throttle blade and cause the ECM to decrease the IAC number to compensate and attempt to hold the programmed idle value.

After you've made a 2 or 3 quarter turn adjustments, take a look at what your TPS has changed to. You will have to bring it back into tollerance also (.40-.44).

I prefer to keep my IAC in park neutral at around 10 or slightly lower, when you shift into gear it will increase to somewhere in the 20's.

 

[2 QK 4 U]

Thanks for the tip.

I couldn't get my IAC below 21 and then when I reset my TPS it went back up to 29...Is this oK?

Thanks,

 

[TurboDave]

Thanks for the tip.

I couldn't get my IAC below 21 and then when I reset my TPS it went back up to 29...Is this oK?

Thanks,

Should be OK. At least it's a lot better than it was.

 

[2 QK 4 U]

It drives a lot better now.

Got another problem...I put new valve coves on with K&N breathers and the red oil that I put on them is blowing all over the covers and smoking off the headers....Very Nice......I'm finally getting frustrated now

 

[TurboDave]

It drives a lot better now.

Got another problem...I put new valve coves on with K&N breathers and the red oil that I put on them is blowing all over the covers and smoking off the headers....Very Nice......I'm finally getting frustrated now

I never oiled my valve cover breathers, I figured they'd get plenty on their own from the inside out!!

 

[2 QK 4 U]

So do you think I should get new breathers or how would I get the oil off of the existing ones?

 

[TurboDave]

So do you think I should get new breathers or how would I get the oil off of the existing ones?

I would just take some simple green, and wash the oil all out of them.

 

[Bird of Prey]

Sorry to hi-jack this thread but...

my problem is, that i can't set IAC lower than 80, because when i set the screw at the farthest position backwards, the throttle doesn't go as far back as the screw does.

any opinions on that?

help much appreciated!

matt

 

[TurboDave]

Sorry to hi-jack this thread but...

my problem is, that i can't set IAC lower than 80, because when i set the screw at the farthest position backwards, the throttle doesn't go as far back as the screw does.

any opinions on that?

help much appreciated!

matt

When adjusting the screw "back" you are causing the IAC's to want to move higher. You are closing the throttle by doing this, the computer senses a momentary drop in rpm because of the closing throttle and increases the IAC in an attempt to keep the rpm at commanded value.
Turning the screw "in" to the point where it starts opening or pushing against the throttle stop device at some point the extra air will cause momentary increase in rpm and the computer will then start lowering the IAC to compensate.

Do this in small steps. Once the screw engages the throttle stop, make one or two turns at a time, and makes sure to re-adjust your idle tps value to within spec each time or you'll gain nothing.

 

[Blazer406]

When adjusting the screw "back" you are causing the IAC's to want to move higher. You are closing the throttle by doing this, the computer senses a momentary drop in rpm because of the closing throttle and increases the IAC in an attempt to keep the rpm at commanded value.
Turning the screw "in" to the point where it starts opening or pushing against the throttle stop device at some point the extra air will cause momentary increase in rpm and the computer will then start lowering the IAC to compensate.

Do this in small steps. Once the screw engages the throttle stop, make one or two turns at a time, and makes sure to re-adjust your idle tps value to within spec each time or you'll gain nothing.

What he said....

Just remember... if you want to lower the IAC numbers.... tighten the screw.... that actually opens the throttle plate a little....

Do the opposite ...if the numbers are too low.. and you want to raise the IAC values.

As TurboDave said.... small steps... don't adjust too much without re-setting the TPS.

 

[Bird of Prey]

haha... thank you guys!

Did this exactly like you said, today. Before reading the posts... iac is okay now at approx. 10, tps i set to 0.44

thx!

and what is more... this fits in this thread: i guess one header / exhaust - gasket is finished. so the car stumbles at acceleration. i will fix this next. anyone done this before?