You advise that when your vehicle is stopped and you raise the rpm to 2000 rpm, then you can get it to misfire. That’s probably a good time then to try to locate which cylinder is the issue, by pulling off a lead to see which one causes the misfire to stop.

 

Thanks for the idea Bex but I mistyped. It doesn't happen.

I have now corrected the typo - sorry to mislead you.

 

I'd start by putting a fresh set of plugs in, and if that doesn't fix it, swap the coils/leads out one by one. WHY were the coils & leads swapped 30,000 km ago, were the replacements SGP or aftermarket?

 

2009 Swift auto 2WD 300,000km serviced regularly inc plugs and the pair of coils & leads replaced about 30,000km ago.

The car runs perfectly under all conditions except when idling and/or stopped at traffic lights. The misfire is erratic in that it can be absent for quite a while in stop-start traffic, say a half hour, and may misfire momentarily, then be absent again for a while. When stopped and the eng RPM is raised to about 2000rpm, the misfire does NOT happen. The engine has never cut out.

The MAF sensor and throttle body have been cleaned and harness plugs thereabouts checked - without any positive or negative change.

No CEL showing ever.

Good morning, you say you have 300,000 kilometers. It is logical that at these kilometers there would be some wear on the engine in general. I suggest measuring cylinder compression and comparing the results. It is very likely that the engine will consume a certain amount of lubricant at these kilometers. If this happens, it has a direct impact on the operation of the spark plugs and the engine in general. Diagnosis is easy. It starts with this. Your mechanic knows exactly what to do. I'm George

 

Thanks for the replies folks.

One of the coils failed back then and new a aftermarket pair, 4 plugs and plug leads were fitted - 2 plugs per coil. Swapping the coils around may shift the intermittent misfire when idling but pinpointing which cyl is almost impossible as it only misfires for a second or two at a time - and not every time it is idling.

Yes, 300,000km is a fair amount and sure there's wear in there. It uses a bit less than 1 litre of oil in 10,000km. However, the car performs perfectly under all driving conditions. In my experience, if plugs, coils or leads are failing it will show up under normal driving conditions, not just very intermittently when idling whether in N or D.

And yes, I should replace the plugs just to rule them out and do a compression test - next time I have time, which won't be soon as it's 425km away.

In all my searching I haven't found/read of the same problem with an RS415 Swift. I'll report back when I have more to add.

 

I would rather use a scope and record the ignition and injectors for errors..

 

Agreed, but I don't have access to a scope and the misfire is so irregular that it's not 'regular.'

 

I've ordered a new idle speed air control valve, which are quite cheap on ebay. I'll report back when fitted in a coupla weeks.

 

Idle speed air control valve!? I can see that causing an idle speed variation, but a misfire, not so much. Makes me wonder if your definition of a misfire matches mine. Ah well, who knows...

 

Agreed. I don't normally 'throw parts at a problem' but it's a cheap and easy item to do.