why is my timing mark jumping around now?

[maca]

thanks guys
I will try another timing light and try to stall it up in gear to see if its doing it under load

[BrazilianZ28Camaro]

Two points:

If your timing light isn't self powered, you need to plug it directly on the battery and NOT on the alternator's terminals . You can use a spare battery for the timing light to isolate related problems. Make sure your timing light works with multi spark ignitions, because some don't.

Once, I had this problem os a POS 4 banger, idle timing would jump 10 degrees , I changed the alternator and the problem was over.

Hope this helps

[maca]

I tried the timing light on a different car and it was 100% fine but my car I am having issues with has the battery in the boot and I have been using the alternator
I will give a battery a try
Cheers

[maca]

Tried a different battery but no luck.
I noticed the MSD crank trigger is a magnetic set up.
Is my factory crank angle sensor magnetic too? the sensor crosses over holes cut in the flex plate so perhaps that's why MSD said it will not work as it may not magnetic

[maca]

I checked the timing chain and its fine which I am very happy about.
I pulled the dizzy apart and may have found something. It looks like water or moisture may have gotten in at some stage.
The sensor looks a little rusty. Can I sand it clean or do I need another one?

[Circlotron]

I have seen some timing lights get a bit twitchy if the signal picked up from the plug lead is a bit to strong. Try opening up the clamp to reduce the signal and see if it comes good.

[maca]

You wouldn't believe it!
I was just about to undo the rockers to release the pressure off the cam and check it for end float as I had the MSD dizzy put on a dizzy graph and tested 100% fine. I brought a Chinese cheap nasty dizzy off ebay and put it in last night. Timing is now solid and working well. Now what do I do?
I cant run one of these cheap dizzys as I have had them in the past seaze and give me all sorts of problems but its the only one that's fixed the problem. Not sure now.
I will look at both dizzys today side by side to see if the shaft is longer or the base is thicker on one as the cheap dizzy has no play in it at all.

[hysteric]

Have you checked the reluctor gap?

Hysteric

[maca]

No hadn't thought of it as I have had it checked in a dizzy graph and it ran fine before but that's something I will do for sure now you mention it.
I have noticed the cheap dizzy has a shaft around 4mm longer and being a cheap dizzy the shaft is fairly stiff so it takes the slop out of the rotor button