1992 Marelli misfire, need help
#1
1992 Marelli misfire, need help
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
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
#2
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...
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...
#3
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...
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...
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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
#10
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.
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.
#11
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.
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.
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...
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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.
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.
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