Good morning all,

With my cooling issues fixed, I took the newly acquired 92 out for a spin and noticed that if i try to accelerate past 2500 rpm, she starts to buck and backfire. Idles smooth and does fine up to the 2500 mark. I can't tell if its both banks or just the left since that was closer to me.
I've checked the vac line to the ecu, verified coolant temp sensor function and adjust the TPS to .34V at idle. It's still got the twin coil setup. Does anyone have ohm specs on these coils so I can test them? if they check out, next step will be to pull the cap to check it and the rotor but I'd like to do the easy stuff first to eliminate them before diving too deep.

Any other suggestions?
Kevin
88 XJS
92 XJS
14 XF

 

Waste of time measuring the resistance of the coils,,as they only cost a few bucks each... Basically generic parts...

What condition are the HT leads? The Marelli suffers from some problems when the HT leads are cracked etc.

The rotor and cap can fail but that is rare (apart from a dizzy fire but that only comes if maintance is neglected). The same counts for the dizzy itself. It rarely adjusts itself...

 

The leads don't look bad, no visible cracks in them and no signs or sounds of arcing (ran it in the dark) while fiddling the wires. I got a partial service history on the car and last documented plug/wire/cap/rotor service was back in 04 and 20k miles ago so its def due. i'll go ahead and change plugs and HT leads and take a look at the cap and rotor since the wires are coming off anyhow. Any tips to get to 1A/B without unbolting compressor?

 

Nope. You can only unbolt the compressor. Some people have made some weird tools to get the plugs undone but the safest way is still to undo the 4 compressor bolts...

 

Daim is right ohms for a coil is useless unless you are sure they are original coils as ohm spec can be different even for plug compatible coils.

If you have not changed the spark plugs do that first.

 

Is this the type you need with the metal pin inside? I have two...they didn't work for my car (different plug) so I bought another set that did.

 

The are the correct Marelli ones. Should be a 4 pin connection IIRC.

 

Ya but the bottom wire plug was different, if he needs that type I could send them.

 

Yes sir, those are the coils I have (Marelli), I'm going to do the plugs and wires this friday as well as check cap and rotor. The car was well driven and maintained for most of its life but then sat around for long periods of time over the last 8 years. I was very happy that I could get the check engine light to go off by fixing issues instead of putting black tape over it like the last owner did. I also need to tackle the dead oil pressure gauge but having a hard time justifying $65 for the sensor that looks just like a $8 ford part and does nothing special

 

Work through the issues one at a time and before you know it she'll be running like an Omega (I'm not a Rolex fan).

When I renovated mine I had changed the plugs only a few hundred km's before she was taken off the road, When it came time to start her up again she ran on 8 cylinders, pulling all the plugs and cleaning them and voila 12 cylinders.

 

And even if you need to take the engine out *ahem* do it task by task.

The Marelli system is a lot less hasse than the Lucas one and looks tidier. It is also less special. Of course, original dizzy caps are basically inobtainable but they unite us Marelli owners with Diablo drivers... The cap and rotor are identical. And Lambos will always get parts. Just will cost a few bob.

Even the ignition modules on the radiator cover are available - again! Marelli has started a reproduction run as they are common to nearly all 6 cylinder Marelli cars (and there are a few of them, like the Alfa Busso powered cars etc.).

I was reading through a borrowed Marelli book a few days ago regarding symptomes etc. One misfire cause can be a slowly dieing sensor. The front one on the engine. It is rather easy to access. They are not cost. You can check it's function quite well...

 

True about lambo parts, I was about to order new old stock marelli amps from a place in California that does ferrari/lambo etc but I found a suitable part on ebay (VE520225 Cambiare) will post results when I get them.

 

The Marelli amps are Bosch 0 227 100 124

And the Lambo guys are buying Jaguar V12 parts, ironic eh.

Here is a pic of a Marelli rotor and cap from a 365 Ferrari, the rotor is similar but for the mounting and the cap is identical.

 

Ah, course, the rotor can't be identical. That was a mistake. If you compare the Marelli dizzy to a Lucas one, they are basically the same, just one lacks all the crud and is basically empty. Yeah, course.

Regarding Lambo owners buying Jag parts: no wonder! The same aftermarket dizzy cap costs (herr) for Lambos something like €250. For a Jag €80. I would save €170 if I could any day!

But when out dizzy caps are sold out, you can be sure Ferrari and Lambo owners will still get supply. If not we'd have to see about getting the dizzy caps refurbished or newly 3D printed.

 

Cleaned up terminals, no signs of cracks or carbon tracks so its gonna go back on once I get plugs changed then new wires going on as well.

 

That cap looks in a remarkably good condition! Contacts look nearly new!

 

That looks like an original Marelli cap, guard it with your life.........

What is the rotor like?

 

Yeah the rotor can suffer from shortening out... There were some solutions to this.

 

Yes sir, it is indeed an original Marelli cap. Rotor is very clean as well, I just took some sandpaper to the terminals to clean them all up. per service history the cap was replaced at the dealer in 2005

 

Okay, dizzy seems unlikely.