Jumping timing

[capri_turbo]

I've had the MJLJ running for over 2 years now with no issues, but recently the engine has become harsh... Just checked the timing with the Jolt unplugged and I find the timing is jumping 9 degrees... not drifting around, but a jump and the same 9 degree jump at any revs. Most of the time it's at 19 degrees, then it'll jump back to 10 and then straight back to 19.

I have ruled out the EDIS 4 as I have a spare which does exactly the same thing. When I first installed it all I had a rock steady 10, so I'm thinking the bracket should still be fine, although I am going to make up a new bracket from heavier plate, but as the timing is jumping a steady 9 degrees I'm doubting it's the brackets either.

Could it be the VR sensor? it's the one bit I don't have spares of.

[BRUCEROE]

It sounds to me, as though its jumping between programmed spark and (10 degree) limp mode. I doubt it is the VR, because losing sync there would put your timing all over. I'd suspect the MJLJ or its wiring; at this age, a loose or tarnished connection could do it. Cleaning or wiggling the chips that plug in might bring it back for a while. If so, they need to be soldered instead. Does it run a straight 10 degrees with VR off? Bruce Roe

[capri_turbo]

There is definately no problem with the Megajolt unit as it was disconnected and running ONLY on the EDIS. I have used 2 different EDIS4 units and got the same 9 degree jump... always 9 degrees... measured at idle and 3000 rpm... 9 degrees every time. With MJLJ connected I still get the 9 degree jump but from the programmed 14 degrees idle advance giving me 23 degrees at idle... not good.

Another thing I should be able rule out at this stage is my digital timing light. I should be able to borrow another one next week to double check, but I really don't think this is the issue as the car isn't behaving... all symptoms are it being over advanced... also when holding a steady 3000 rpm without the MJLJ, each time the timing jumped, the exhaust note changed slightly leading me to beleive the figures the timing light is giving me.

[NITROPIXIE]

I wonder if its a coil pack issue or what plugs are you running?? Resistive ones?? Maybe getting the odd bit of interference from somewhere.

Is ypur triggerwheel solidly mounted or is it on a crankshaft damper?? If so what condition is the damper??

Ryan

[capri_turbo]

using NGK AP7FS plugs in a 2.1 Pinto engine. Running Motorcraft 8mm silicone leads.

Trigger wheel is bolted to the front crank pulley which is a solid cast steel item so no chance of any movement there as it's located to the crank by a woodruff key.

[NITROPIXIE]

Try changing your plugs to some equivalent resistive ones. I believe they are APR7FS. Its a good chance your getting interference from your spark plugs causing an erratic signal/operation.

This, i would suspect, is the problem but i do not gaurantee it. Cheaper than a replacement coil pack unless you already have a spare lying around.

[capri_turbo]

The leads are resistive, would having resistive plugs not be too much? The PIP and SAW lines are shielded and the EDIS is 2 feet away from the plugs. I will certainly get some plugs and try it though.

[cng1]

Just because your trigger wheel is bolted securely in place that doesn't mean that it isn't eccentric enough to cause the EDIS module to resync. I don't know what your crank sensor bracket is like but I've seen alumnium ones wobbly sufficiently to confuse things.

[capri_turbo]

trigger wheel is concentric... VR sensor brackets are aluminium. The thing is, when I first set all this up it was rock steady 10 degrees. I'll make up new brackets in the next few weeks from some stainless steel shet I have here. I should be able to fold the edges to give more rigidity.