308 Missing and backfiring - Ferrari Life
 
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post #1 of 7 Old 06-26-2014, 10:45 AM Thread Starter
 
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Missing and backfiring

Hey Guys,

A friend has a car here which is a 79 308 GTS. There are some issues with the car -

1). The car misses at idle.

2). On a steady rpm of 2000rpm or 2500rpm or 3000rpm for over minute, the car seems to backfire/splutter.

Any idea what i need to look out for ?

EDIT : Also any idea, how do i check if the car is a 2v or a 4v?

Thanks

Last edited by Indrojit; 06-26-2014 at 11:31 AM.
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post #2 of 7 Old 06-26-2014, 11:47 AM
 
Join Date: Jun 2013
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79 is a 2V.


one dizzy or two?


Check plug leads and especially the plug extenders as they have a habit of grounding to earth and causing misfires. It will misfire when revving!!
Make sure you use the red ones.
If the front bank fire and the rear bank miss (or vice versa) then you may have distributor problems.
Check for fuel starvation ie fuel pump,blocked jets etc
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post #3 of 7 Old 06-26-2014, 12:22 PM Thread Starter
 
Join Date: Jun 2014
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Quote:
Originally Posted by 246dno View Post
79 is a 2V.


one dizzy or two?


Check plug leads and especially the plug extenders as they have a habit of grounding to earth and causing misfires. It will misfire when revving!!
Make sure you use the red ones.
If the front bank fire and the rear bank miss (or vice versa) then you may have distributor problems.
Check for fuel starvation ie fuel pump,blocked jets etc
Its got one Dizzy and two coils. Would this dizzy have points or electronic ignition?

Yes it does misfire when revving.

Its done only 62000miles. Should we change the timing belt and water pump ? Why does one need to lock the cams while doing a timing belt change ?
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post #4 of 7 Old 06-27-2014, 02:38 AM
 
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Fit a timing strobe lamp to each plug lead while it is running. No light means you need to look at the cap, distributor or rotor arm.


If the light flickers and you have fouled plugs then the plug lead or extender is suspect.


There is no points in this dizzy, it operates on the VR sensor and reluctor wheel with ignition amplifiers / coils. One for each bank which is why you need to check if the front or rear bank is causing the misfire, Be warned about where you buy these from as most are not suitable for the 308.


VR Sensor inside dizzy
Variable Reluctance sensor for Marelli contactless S type distributors
Gap between reluctor and sensor 0.25-0.4mm



Ignition Modules one per bank
Magneti Marelli BKL 1A, four terminal HEI module
Type code 940 038 521
Order code 64833010

Coil one per bank
Magneti Marelli BAE 207A, inductive coil for transistor ignitions
No external resistor required with BKL 1A
~0.8Ω Primary Resistance
~9KΩ Secondary Resistance


Its not absolutely necessary to lock the camshafts when doing a belt change so long as the timing marks on the cams all line up when refitting and tightening up. When was the last TB change done?
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post #5 of 7 Old 06-27-2014, 09:55 AM
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Location: Near Olney, MD
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Quote:
Originally Posted by 246dno View Post
79 is a 2V.



Check plug leads and especially the plug extenders as they have a habit of grounding to earth and causing misfires. It will misfire when revving!!
Make sure you use the red ones.
1+ on the plug extenders. You can just pull them out one at a time and just look for black marks or tiny pin holes on the extenders. You can just wrap the suspect extender with electrical tape and see if the problem goes away. I had a similar problem and you can search my old posts for pics and also some good suggestions on where to get the extenders cheap.

I hate to admit this but I filled the pin hole in the extender with RTV and then a couple layers of black electrical tape a couple years ago and I'm still driving it that way!

------------------------------

Life is Good!
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post #6 of 7 Old 06-27-2014, 10:05 AM Thread Starter
 
Join Date: Jun 2014
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Quote:
Originally Posted by 246dno View Post
Fit a timing strobe lamp to each plug lead while it is running. No light means you need to look at the cap, distributor or rotor arm.
If the light flickers and you have fouled plugs then the plug lead or extender is suspect.
Will do that. The cap and the rotor have never been changed in its life on this car. So will change it for good measure.


Quote:
Originally Posted by 246dno View Post

There is no points in this dizzy, it operates on the VR sensor and reluctor wheel with ignition amplifiers / coils. One for each bank which is why you need to check if the front or rear bank is causing the misfire, Be warned about where you buy these from as most are not suitable for the 308.


VR Sensor inside dizzy
Variable Reluctance sensor for Marelli contactless S type distributors
Gap between reluctor and sensor 0.25-0.4mm



Ignition Modules one per bank
Magneti Marelli BKL 1A, four terminal HEI module
Type code 940 038 521
Order code 64833010

Coil one per bank
Magneti Marelli BAE 207A, inductive coil for transistor ignitions
No external resistor required with BKL 1A
~0.8Ω Primary Resistance
~9KΩ Secondary Resistance

I was thinking of getting them from superperformance.co.uk Would that be fine ?



Quote:
Originally Posted by 246dno View Post

Its not absolutely necessary to lock the camshafts when doing a belt change so long as the timing marks on the cams all line up when refitting and tightening up. When was the last TB change done?
Well the current owner has this car for the last 4 years. He hasn't done it. I really doubt if and when it was done last by the previous owner.

Does locking the cams in place, make it easier to do the belt change ?

How is the quality of the carburettor kits that are offered by superperformance.co.uk?
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post #7 of 7 Old 06-27-2014, 11:51 AM Thread Starter
 
Join Date: Jun 2014
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A good and reliable source for parts for the car please ? The chassis number of the car is F 106 AS *28863*.

May i have details about the car like where it was made and other specs ?
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