I have posted this problem in a few different sections as I don't know which one suits it best.

I have an LS1/4L60E powered Holden Commodore which has had a fair bit of work done to it, but I am currently experiencing a problem with the trans shifting from 1-2 a lot earlier than the shift point. I have set it to shift at 6400rpms at WOT but it will shift between 3000-4500rpms. This problem started happening after I installed a cam, the specs are as follows :

Duration - 233/233
Lift - 550/550
LSA - 114

I have my idle set to 850rpms which has a really lumpy/aggressive idle. After idling for a little while it will set off the following codes :

P0121 Throttle Position Sensor Performance
P0154 H02S Circuit Insufficient Activity Bank 2 Sensor 1

I have disabled these codes using LS1Edit so the codes don't appear anymore, but the problem still exists. I am wondering if anyone else has had a similar issue to what I am experiencing and what the outcome was. Sometimes when I first turn the car on if I drive around without sitting at idle until the car warms up I can put the foot down in first and it will shift correctly but then it will eventually begin to shift early once I have driven it around for a while.

Could my problem be due to the size of the cam/lumpy idle interfering with the sensors? When I took it into the dealer they said that the Throttle Position Sensor seemed to be working fine but it was like the transmission wasn't responding correctly to the throttle. Is it possible that the cam interferes with the sensor and then the computer goes into a safe mode where it doesn't listen to the TPS?

Any help will be greatly appreciated.

Brett.

<small>[ March 13, 2003, 09:14 PM: Message edited by: Brett SS ]</small>

 

Have you looked at the MPH (KPH?) 1-2 upshift
setpoint? It should upshift (at WOT) at
the first it hits, either MPH or RPM. So
if MPH is triggering it (stock setting is
like 38MPH, and even 40MPH is earlier than
6KRPM on my car) then no matter how far you
push out the RPM threshold it won't matter.

 

If you messed with the idle screw to up your idle instead of using Ls1edit that might be the problem. I doubt it was the cam. I have the hotcam and it seems to be one off the worst for idle but mine does fine and it shifts a little funny from 1-2 (like 300rpm less than i have set in edit) but i think this is a common problem. Good luck though....someone else will probably be more informative.

 

Thanks for the replies guys. <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

jimmyblue,

I have looked through all shift tables and the settings for WOT and all of the RPM and MPH settings are correct. It doesn't seem to be these settings as if I start the car from cold then drive around without idling too long until warmed up it will shift properly at WOT. It's after it idles for a while in traffic that it starts not shifting correctly.

CustomTA,

I have set my idle using LS1Edit to 850rpms but we did crack the throttle blade open a tiny bit to help with starts. I have also raised the IAC values a bit from stock, could this be contributing to it?

If anyone else has any suggestions then I would be happy to hear them.

Brett.

<small>[ March 13, 2003, 10:58 PM: Message edited by: Brett SS ]</small>

 

check your tps sensor ( throttle position sensor).
either check it's voltage using a scan tool or swap it out with a friends and see what happens.