Marelli AEC 104 B-660 problems

I'm currently trying to fix a problem on a Ferrari 400i.
I think i could use some help or some shared experiences from people who had the same sort of issue.

Right now the engine hesitates dramatically, it still starts up and drives but unregardless of whatever RPM, all of a sudden it misfires really bad. Could be at 2000rpm could be at 5000rpm.
The ignition system is a Marelli AEC 104 B-660, coil is Marelli BEA 202B. Distributor is Marelli s158 with pickup sensor.
Before doing all kind of things, someone might have experienced the same kind of problem and could point me into the right direction.

Can a malfunctioning AEC 104 lead to hesitation issues in first place or will a broken AEC 104 always lead to a complete stall?
Are the pickup and or coil prone to fail or did someone ever had this issue and traced it back to a malfunctioning rev limiter that kicked in at random RPM's?

Help would be highly appreciated

 

It's really missing and on all cilinders at the same time. Feels really like a ignition problem because it's just instantly missing and picking up, it's not surging. Weird thing is that applying more throttle if it misfires cures it for a second or something.
Did all the K-jetronic fuel pressure tests allready (because i have the equipent for it and not all the specific equipement for diagnosing ignition related problems) just to be sure and everything seems to be in spec injectionwise...

 

I guess you mean the mechanical advance mechanism. It doesn't really feel like an advance issue to me but more like an electronic issue.

 

Guess you were right, the helical gear running the distributor shaft has a lot of end play. Worst part of the story is that this was partly causing the misfire. Static ignition advance was set at 40 degrees! At random rpm the shaft started floating giving it another 20 degrees of advance. I think it's a miracle the engine still has pistons and conrods.
Traced it by putting a degree wheel on the harmonic balancer and you could clearly see it was randomly bounching up and down 20 degrees.
I could not really figure out wat was causing the end play, is it the bearing underneath or is it where it meets the distributor shaft? For now i shimmed it out to do some testing and advance is stable (and offcourse set to 8 degrees static advance).

Still not running perfect but at least 10 times better. I think this is going to be a repair that will end up revealing an interesting history of 'workarounds'.

 

Does someone know if these 400I's were originally equipped with solid copper core HT Leads or with spiral wound? This car has solid copper core but it looks a bit odd to me for an 80's car with CD ignition and there has clearly been messed with them as well. Just want to know if these could be the original ones or if they had been replaced in the past by wrong copper core leads.

 

Thanks!

I will replace the HT leads for sure. Would replace them with spiral wound in any case but i was just wondering if solid copper core was original, especially in combination with electronic CD ignition. So you know for sure that they were originally equiped with spiral wound? In that case i know that they have been messing with the leads in the past.

 

Car was pretty much running ok now. No real bad misfires anymore, stable idle and so on.
Only thing was it would not rev beyond 5000rpm, than it started to surge. At this point i knew most of the ignition was okay so the only suspects were the AEC 104B unit, VR-sensor and the coil. Did some tests and found out it was a malfunctioning AEC 104.
Replaced it with an MSD 6AL-2 and blaster coil and now it's running like a dream. Also replaced the spark plugs with Iridium ones and made a nice set of spiral wound HT leads. Rev's easely to 6500 rpm, no misfires, no surging, everything stable.
In the end i think the AEC 104 was allready malfunctioning for a while and that there were numeous of workarounds trying to fix the running issue which resulted in a dangerously advanced igntion timing worsened by excessive distributor play.

Thanks for the advices!

 

To finish it up and make it look a bit less horrible i finished the 6al-2 with some wrinkle paint. Makes it a bit more attractive with the bonnet open.
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A question regarding a 400i with an MSD ignition.
I'm currently keeping myself busy with a 400i that has an older MSD 6A installed. It still uses the original 3 terminal BAE202B coil. Should this coil be replaced with an MSD coil? Is this 3 terminal coil function wise identical to a 2 terminal MSD coil (something I can't really believe)?

 

Thanks alhbln, I will replace it with the correct MSD coil.
Can you explain what the exact difference is between these 2 coils and why the AEC104 needs the 3 terminal coil and the MSD not?
What happens in this case because of the separate primary ground? And will this reduce spark output, can it lead to a malfunction in the MSD unit, will damage occur in the BEA202B coil in the long/short term?
Your help in understanding this is most appreciated!

 

Interesting.
I noticed that they removed the yellow wire that is originally connected to B+ on the coil and wired a separate wire from the MSD orange wire to B+. (that probably has to do with the high voltage on the car's battery supply you're referring to)
They used the red wire that is originally connected to K as 'MSD's Coil -.
It does seem to work this way because it had no ignition related problems but I expect it to be not a recommended setup.? K is not wired to ground in this setup.

Correct me if i'm wrong. The output of both coils are somewhat equal because they both have about the same winding ratio's and in CDI applications the coil is just a transformer contrary to a coil in an inductive setup where inductance is an important value?