1990 Testarossa intermittent issue

Ok guys, I have a 1990 Ferrari Testarossa with 23k miles on it, and it is a U.S. spec model with the Capristo 3 exhaust with original Cats, and I seem to have a very strange intermittent passenger side engine shut down issue.

I have been chasing this issue for quite awhile as I have been regular driving this car in hopes what ever the issue is would just stay, because it would be much easier to find.

Here is the criteria.

Not Heat Related, as it did the same Summer, Fall, and Winter.

It tends to be Split Second direct Off/On to feel the whole right bank is off, so it isn’t a couple cylinder misfire.

After awhile this will tend to affect the spark plugs on that bank with a rich appearance, and then the intermittent will last longer with the Cold Start or Restart sometimes not firing on that whole right bank. But when the bank is not firing, I can pull the coil wire while running to reveal the coil ks firing, and I can affect the resistance/firing change by hold thing coil wire a bit of distance from the coil for a longer arc.

These longer timed symptoms change instantly with a new set of plugs in the right bank, until it decided to do it again over time, while still having the split second Off/On that has no rhyme or reason as far as conditions or timing.

I have changed Plugs, Plug Wires, Dist Caps/Rotors, Spark Plug Insulators, Fuel Pumps, Fuel Regulators, Fuel Accumulators, Bosch Modules, Ignition Relay, while checking grounds and bad or loose electrical plugs/harness with the wiggle/Pull test to find nothing.

When it is in the longer right bank dead symptom, I can pull the left bank coil wire for an instant stall, but I can pull the right bank coil wire to remain running with some running difference by extending the coil fire arc to the coil wire.

I have also swapped sides with the coils and Bosch control boxes, the car runs as smooth as silk 99.9% of the time otherwise, and the intermittent is basically an Instant On/Off when it happens.

Could it be a Spark Plug resistance issue, and the Off/On is way too snappy for a fuel leaning issue, which I am running the NGK Iridium DR8EIX

 

I have inspected the fuse block and connections also, and don’t see any sign of anything running warm like that, but it is also not a lack of fuel pressure thing by the speed if the split second Off/On that isn’t common to fuel pressure drop and built up.

The car doesn’t miss a beat or stumble, it is literally a quick Off and right back On.

 

Thanks man, the issue is catching it messing up, because it is totally random and in split second intervals, which is why I was hoping that it would just finally stay dead. Lol.

But it’s been doing it for about 6 months with no rhyme or reason, which is why I first started chasing loose connections or grounds first, as I was thinking it may have been bump related.

 

Can anyone tell me if the Injection Units may have a fuel cutoff for deceleration? After chasing all the electrical to find nothing, and the fact the coil appears to be firing at the time of issue, it could perhaps be a quick decel shutoff?

I don’t think it is a fuel pump, as the triggering off and on is literally split second off and on, rather than a progressive lack of fuel pressure stumble, which now makes me question if there is s head unit decel cutoff that is faulty or randomly triggered?

 

Thanks man, I will definitely check that out, and greatly appreciate the effort with putting the advices together

 

Steve, I really want to thank you for the help, and I found that may have fixed me up. Turns out that I wasn’t making the best connection on that plug for tout or corrosion reasons, but I found that during the intermittent issue, the car would come back alive when I touched that plug.

There wasn’t any issues that could be found with the harness or plug, so it appears I may just wash the car too much and it lost connection over time.

 

Yes, all is basically good overall, just had that issue that was causing my problem, but it did allow me to check everything along the way with also performing preventative work along the way.