Timing Mark wanders AQ131D Where do I start?

[E-vader]

I have a 1989 AQ131D, recently replaced cap, points, wires, etc but cannot set base timing --- the mark wanders about 10 - 20 degrees. The best I can do is set it at 6 btdc on the low end but it bounces to 20-25 btdc and then back to 6 btdc over and over. Is this a belt/tensioner issue, a distributor issue or other/both?

Where do I start diagnosing this problem?

I have what appears to be OEM Bosch distributor.

 

[Maclin]

Re: Timing Mark wanders AQ131D Where do I start?

What rpm is the engine idling at when you are looking at the timing? Cannot be much above 800-900 or the mechanical advance may be kicking in. The engine will also climb in rpm if the mechanical advance starts to come in.

Check the distributor mechanical advance by moving the rotor left-right with the cap off and see if it snaps back or can move around freely, that would indicate whether or not the mechanical advance springs are working to hold it back.

After that I would go after the tensioning.

 

[bruceb58]

Re: Timing Mark wanders AQ131D Where do I start?

What is your dwell set at? Have you changed your points lately? Measure the dwell with a dwell meter and confirm that it is steady before you go onto anything else.

Timing belt tension would be the next thing I woud look at since the distributor is run off of it.