Currently trying to solve a misfire issue, I have narrowed it down to injector no 1.

Whilst the engine is running if I pull the electrical plug on injector no1 there is no effect to the idle, indicating that the injector is not firing.

I tested this by swapping the injectors around but to no avail, this does however show that it is not the injector at fault.

Looks like it could be wiring/ecu. Has anyone else had this issue, if you have, how did you cure it?

Cheers,

Liam

If you have swapped the injector and the electrical feed to the injector then that suggests it isn't a fuel problem.

If it isn't fuel then it must be spark, or air.

Have you got compression? Are the ITB's reasonably balanced? Have you got a spark?

Matt

Spark plugs, coil and leads have been replaced. I have a spark, the spark plug on the offending cylinder does get sooted up immediately compared to the other 3 cylinders.
Sure it's not wiring/ecu related if I have swapped the injectors and it hasn't made a difference

Try swapping the injectors connectors e.g. swap 1 and 2. If the fault moves to to 2 then it's likely a connection problem.

use test mode on the megasquirt in tuner studio. why guess?

you can make an injector or spark plug fire without the engine even running just make sure you take the fuel pump fuse out first or it will end badly.

you can hear the injector tick when it is told to fire and you can see if the spark plug works by taking it out the cylinder and running it touching against the block.

if you have swapped your injectors round and the problem didn't move cylinder its not the injector.

next test and see if you have spark. if its even fire and running wasted spark you can get away with swapping cylinder 1ht with 4ht leads and 2ht lead with cylinder 3 ht lead. if the problem moves its either the spark plug ht lead or the coil pack, you can elimate one at a time by swapping parts around one at a time and seeing if the problem moves.

if that fails to identify the fault then it could be a coil driver or injector driver in the ecu but then the ecu test mode will show that up if all the other parts have been eliminated.


if all that is ruled out do a compression check.

p.s. you can also swap injector wire cyl1 with cyl4 and see if the problem moves.

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Originally posted by MikeRJ
Try swapping the injectors connectors e.g. swap 1 and 2. If the fault moves to to 2 then it's likely a connection problem.

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Check the balance of the TBs , I have noticed in the past that it is possible to get them enough out of balance that the engine appears to misfire at idle due to a very rich mixture on one cylinder and then picks up on all 4 as soon as the revs are raised.maybe turn the adjusting screw in a little on the one cylinder and then get them all balanced at a high idle before adjusting the idle screw after balancing all 4.
Paul

Another vote for throttle balance for your dead cylinder issue. I usually fine tune my t/b's by removing the injector plugs one by one and adjusting the balance so that the drop in engine note is the same across all cylinders.

Using this method gives a silky smooth tickover, but if you get the adjustment wrong it's easy to end up with what appears to be a dead cylinder at idle......

Another one here for throttle body balance. Check to see there is airflow and remember you need fuel AND air to make a bang. If it comes back online when you open the throttle then I'd say its exactly this problem.

One more vote for ITB balance! Hold the throttle open a little (1500 rpm should be fine) and see if the exhaust is getting hot on that missing cylinder ... if it is then the injector is firing and fuel being delivered .. that only leaves air balance at idle .. or a weak solenoid in the injector .. but if you have already swapped injectors .... then bingo! Use a vacuum balancer at idle to check it .. and set it.