ignition timing

[mikev]

ok got a wierd one for you guys. 88 4.3 v6 with thuderbolt 4 i think (anyway no points). when setting the timing it bounces around between 8 and 12 degrees. it has new cap rotor plugs and plug wires. so far i checked and it bounces around on all cylinders not just number one and it still jumps around some when revved up to 3000 rpms. any ideas im thinking a bad distrbutor any other ideas guys?

[DON N.]

One Possibility, It Could Be The Timing Chain .

[joseph m. hahnl]

ok got a wierd one for you guys. 88 4.3 v6 with thuderbolt 4 i think (anyway no points). when setting the timing it bounces around between 8 and 12 degrees. it has new cap rotor plugs and plug wires. so far i checked and it bounces around on all cylinders not just number one and it still jumps around some when revved up to 3000 rpms. any ideas im thinking a bad distrbutor any other ideas guys?

"vacume leak". timing chain controls valve timming. due you have the vacume line off the distributer and pluged off? " may be your timming light is the problem.
does it surge? or run okay just jumping around with the light?

[MOP]

Pull the cap back off, firmly grab the rotor see how much you can move it side to side. The bushing in the distributor may be worn, more then a few thousands it needs to be changed. The spark advance is controlled by the IV pack not by machanical or vacuum.

Phil

[mikev]

it seams to run fine just the light jumping around i will have the check the side by side play. i did notice when i replaced the rotor that there was some play in turning it by mabey a couple of degrees is ther supose to be any play in it that way or should it not budge since the advance is controled by the module? also i will try another timing light didnt think of that.

[MOP]

There would be play even in a new unit, I am not sure just how much play you can have, the Tbolt distributer is just a trigger for the pack which I feel could be quite a bit looser then a point setup. I will try to check the manual later to see if and what it gives for a spec on the Tbolt.

Phil

[BUIZILLA]

What brand timing light are you using??

JH

[mikev]

craftsman timing light.

[MOP]

Thank you Jim! The Sears timing light pickups are not shielded well and at times will pickup the pulse from an ajoining cylinders wire, try to get a little slack in the wire so the pickup is not close to any other spark wires see if that stablilizes the timing. My guys say the bushing is very rarely an issue on Tbolt.

Phil