timing advance bouncing around

[jasons4.6stroker]

Ever since I modified my 4.0 into a 4.6 with the larger cam the timing advance has been jumping between 6.5 to 19° advanced having to use the original computer thus it always has a power surge during moderate acceleration. So I would like to see whatyou all have for insight as to what I should look for and or upgrade. Been having difficulty trying to find anyone who can reprogram the computer to adjust to the mods.

[SilverXJ]

What cam are you running?

[email protected] does a great job programming, but your problem may be something else.

[jasons4.6stroker]

I've have a cam from crane cams with a 456 lift. The cam timing is supposed to be .004 advanced but in order to get this motor to run great I had to drop the distributor on #6 tdc plus1 tooth advanced. During initial break in it had amazing pull. Everything on the motor is either fully and thoroughly cleaned and new exception of the sensors on the throttle body however thoroughly cleaned like I've stated. Thank you also for the link I'll give it shot!!!

[SilverXJ]

First make sure your distributor is 100% indexed correctly. The majority of problems come from that. From what you described it could be off. See here: http://www.angelfire.com/my/fan/dist_index.html

Also, check the TPS sensor, MAP sensor and crank sensor.

The lift on the cam doesn't help. What is the duration? And what do you mean by .004 advanced?

[jasons4.6stroker]

The .004 was a typo!! It's supposed to be 4°advanced according the spec card and it's a 260° cam. The crank sensor is new but not the others. It took my friend and I three days to get the motor started and that's the only place it will run.