I lift share with a colleague who has a Suzuki Alto Swift Y reg.
I went on holiday.
He took it for an MoT. It failed due to emissions and some welding was required.
He asked for repairs to be done along with an annual service to get said car through its re-test.
He gets the car back with a full MoT, with an oil change, new filters and new spark plugs.
It was running roughly. he spoke to garage. Garage said that's because we had to reset the timing to get the emissions sorted.
The MIL came on a few days later.
He took car back to garage last saturday. They put it on their diagnostic machine.
They then proceed to adjust the timing and reset the MIL.
Car was still running roughly.
I then come back from Holiday.
The MIL light came back on a few days later on Monday. (he finishes work after garage closes, so earliest he could take car back is next Saturday.)
I offer to plug my own EOBD reader in to tell him the fault code.
Comes up as PO304. which is misfiring No 4 cylinder.
I proceed to remove No 4 spark plug and inspected it.
The electrodes were touching completely with no air gap.
I look up on net to find out what the spark plug gap should be for a Suzy Swift Alto. This is 0.7 to 0.8mm.
I then get feeler gauges out to set the gap to 0.75mm and refit spark plug.
I then reset the MIL with my EOBD reader. car now runs sweet as a nut.
I reckon one of the new spark plugs must have fallen and hit the floor, causing the earth electrode to make contact with the nose electrode.
Is it really beyond the wit of a vehicle technician to know that a P0304 codes does not point to a timing issue, that it actually points to a problem with a misfiring no 4 cylinder? Given that the car has a mechanical distributor cap, logic should say that the problem is usually an electrical fault between the 4th output of said dizzy cap and the spark plug?
Goodness only knows what they would have come up with Next Saturday had he taken it back there.....
Stephen.