This is for a 6spd vette 1990.

The car is a TPI corvette with hot cam, lpe heads, headers.
The car is tuned with a wide band 02, aswell as looking at the BLMs ( by a tuning company ) and my BLMs are at 129-130 all the time.

My TPS is at 0.59volts. Due to my idel rpm witch is set a bit higer to 900rpm. ( the 1991 vette has a "none adjs TPS". )

When you cruise at low speeds, around 15-20 mp/h ,first or second gear, and you just touch the gas pedal. The car jumps back and forth, and you have to go to 1800rpm before you have a smooth run.
Its almost like there is a "on/off" from idle to 1800rpm?
Whery hard to drive in trafic

And when the car is cold the idle goes up and down 700rpm-
1200rpm, it does this 2 minuts, then it settels down.

All this hapend after the car got tuned.

My guess:

To lean at idle?
They took away to much timing.

I looked at the bins, before and after.
They took away alot of spark advance in the 1000/1200 rpm @ 50-80 Kpa area. Stock my car has about 35degres of advance at 1000rpm @ 50Kpa.
The modyfied bin has 20degres @ 1000rpm @ 50 kpa?!

I can send you the bins if that helps.
I will talk to my tuner, but I would like to get som feedback from you first?

 

advancing the timing leans the a/f mixture
retarding the timing richens the a/f mixture
what are the IAC counts (position)?
idle? higher than 50? the ranging can be caused by the O2 richness
and the IAC opens to lean it out (see-saw idle) the TPS voltage
is fine. what is the tps voltage when the craziness starts? IAC?
your trims are dead on... but the LT4HC requires some twisted
tuning, especailly TPI. the lt1/4 seem to adapt better.
what kind of O2 voltages are you seeing while the car cycle idles?
airdeano

 

Thank you alot for the answer, I whas starting to think no one read this post

I try to answer your question as good as I can.

iac counts at idle is 12.
It doenst mater if I am in closed or open loop.
O2 volts is between 450 and 600 Volts.
The jumping starts at around idle-1200rpm when crusing at low speeds, around 12mp/h. Abouw 1500rpm no jumping.
Could that be a due to a lean fuel map at idle?

 

your IAC should be 30-45 and with the cam at 900rpm closer
to 50. this tells me the O2 is seeing low O2 voltages (lean) so
to compensate the IAC closes. another thing is are your throttle
butterflies drilled with a small hole in them? since the TPS is normal
in voltage i am assumming the minimum air rate hasnt been disturbed.
vary your idle speed and observe the IAC as idle speed increases
the IAC should do the same. with no load engine speed 1800rpm
the IAC should be 120ish.
id like to look at the .bin file to see the desired idle speed and
confirming the timing. the trims are awesome, but something is
amiss..
airdeano@mail.com
airdeano

 

I got no hole in the TB. My tuning guy said that driling a hole could help my probleme?
I tried to make a minimal idle set, with the timing cabel disconnected and the IAC. But I hade to open up the TB so much with the idle screw so my TPS started to wander of in the 0.70V area! And I have a 1991 that dosent have a adj TPS.
I also have a slight hesetation when I goet on the gas fast when the car is cold. Could that be a sign of to lean?

Mayby the "startup enrichment VS coolant temp" in tuunercat is something to look in to here?

I mail you the binfiles.
As you can set they tookaway alot of timing in the idle area.

Thanks

 

The non-adjustable TPS sensors can be made adjustable by elongating the screw slots. It's common practice on the '90-92 F-cars and i'm pretty sure the C4's use the same sensor. Hope this helps, sounds like a sweet car.

 

yes i know about the "homemade" adjs TPS done it..

THanks for the comment I love the car, I can toast them in 3d gear hehe..
Now if I only can make the idle and of idle preformace work