LS1 VY hunting not timing issue

[ls1vt209]

Ok here goes,

I am helping a mate with his VY Calais sedan. The car has been converted to manual previously from auto. Car has a 228/228 114lsa .590 lift Comp Cam. Car was previously tuned we believe as a auto with the cam and then converted to manual. The car was hunting around 1400rpm and 1800rpm light throttle and when at idle the revs would jump up to 1500rpm for no reason. We replaced the PCM due to the existing tune being locked. When idling for more than 5 min it would throw a P0121 code

The car was retuned and was good for a day or two.

Now the car is hunting bad again and mil p0121 is appearing again. I don't have a tune here to load yet, will do that tonight along with a log.

The main issue is the hunting. I have flattened the timing in all spark tables to 24 degrees from 1000rpm to 3000rpm and to .36 odd g/s however I am still getting hunting, the spark in the logs does not change, map does not change and fueling is ok.

Does anyone have any ideas at all as to what might be causing these issues, it is doing our heads in.

Thanks Nigel

[macca33]

Have the idle underspeed / overspeed tables been fiddled with? Otherwise, it could be a mechanical issue. Failing that, tuning these things isn't even my profession, so I give up!

Once you've posted log / tune, it may be easier to see where the issue lies.

Also - just googled P0121 and it is a TPS fault, so the one on the car may be faulty, or need a clean???

Good luck with it.

cheers

[rally1]

If it is a TPS code check with the scan tool what the TPS voltage at closed throttle is... if it’s over .4 volt the throttle screw may have been wound in to help with the idle, if so do a TPS relearn ( key off disconnect tps, key on wait 10 sec, key off, reconnect tps, key on) if the voltage is still too high you may need to back the throttle screw off.

If the voltage is to high when you are at closed throttle it won’t go into the idle routines and cause all sorts of issues..

[BLK02WS6]

Post up the tune and log files...