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Rough running and back firing after service

Steveybull

New member
Joined
3 Jul 2016
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4
I just got my 83 911 sc serviced (oil, oil filter, air filter, fuel filter and spark plugs) after this service the car os running rough and is back firing after acceleration, will it take a couple days to smooth out or is this a sign of bad plugs??
 
Don't drive it if it is back firing as this can shatter the plastic airbox
 
Steveybull said:
Thanks l take a look, why would it needing a pop off value now and not before??



its just an upgrade that people put on their airbox, in case of backfires, there have been many cases of broken airboxes and the cheap solution is to order and fit the valve. you might even have one already.
 
Palladium said:
Steveybull said:
Thanks l take a look, why would it needing a pop off value now and not before??



its just an upgrade that people put on their airbox, in case of backfires, there have been many cases of broken airboxes and the cheap solution is to order and fit the valve. you might even have one already.

I havent il order one, but what would of caused this? The car was running 100% and no back firing before the service now it isnt, thats what im trying to find out. One of the old spark plugs was slightly loose would that of released the pressure before hand??
 
Steveybull said:
Palladium said:
Steveybull said:
Thanks l take a look, why would it needing a pop off value now and not before??



its just an upgrade that people put on their airbox, in case of backfires, there have been many cases of broken airboxes and the cheap solution is to order and fit the valve. you might even have one already.

I havent il order one, but what would of caused this? The car was running 100% and no back firing before the service now it isnt, thats what im trying to find out. One of the old spark plugs was slightly loose would that of released the pressure before hand??
You mean spark plug lead? If so push it back on as it'll misfire.
It's got to run better after a service, so you need to take it back. Maybe they've mistakenly swapped a couple of the leads. It could be anything to be honest.
 
take all the plugs out and check the gap, make sure ht leads in correct sequence. speak to garage, sounds very minor, don't worry.
 
Just take it back to the garage .. they will be mortified that its gone wrong and try to fix it .. its probably a plug fault , one of them has a narrow gap that was not spotted on install .
 

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