Misfire on cold start up (2.0 16v 9A)

[VeeDub Geezer 0]

Morning all,

 

Anyone have any ideas as to what might cause our C to miss-fire when cold? It used to do it for a few seconds after starting but it's slowly getting worse. I now have to hold the revs at 2k for 10-15 seconds for it to clear. After this it's fine and pulls as it should.

 

I've tried unplugging the 5th injector with no change. As it's on cold (and cold-ish) starts I'll assume the lambda won't be to blame. Idle is fine when not miss-firing.

 

It's a 9A with KR head but kept the 9A inlet and injectors. Car's on 120k

 

Thanks

 

Aaron

[farrantino 0]

Morning all,

 

Anyone have any ideas as to what might cause our C to miss-fire when cold? It used to do it for a few seconds after starting but it's slowly getting worse. I now have to hold the revs at 2k for 10-15 seconds for it to clear. After this it's fine and pulls as it should.

 

I've tried unplugging the 5th injector with no change. As it's on cold (and cold-ish) starts I'll assume the lambda won't be to blame. Idle is fine when not miss-firing.

 

It's a 9A with KR head but kept the 9A inlet and injectors. Car's on 120k

 

Thanks

 

Aaron

 

Could be the injectors seals, letting in moisture.

[davidwort 0]

It's a sort of lumpy running/mis-fire type thing, I know what you mean, I'd say it's the injectors, but more likely the spray pattern from them being worn. Worn/air leaking seals tends to just cause erratic idling.

Worn K-jet injectors can still deliver adequate fuel in a reasonable pattern with the throttle open from the idle position but be pretty aweful at idle. The problem becomes worse when the engine is cold as it's harder for the fuel to atomise, when you add the crude cold start valve arrangement (more fuel getting sucked into certain cylinders) then initial running at startup can be pretty aweful. My K-jet 16v does the same, new injectors are on the list of things to do.

[VeeDub Geezer 0]

Thanks guys. This was my first thought as I've heard they need refurb/replacement about 120k normally.

 

The hunt is on for salvageable injectors to be sent for ultrasonic cleaning :-)

[davidwort 0]

no, that's the trouble, they wear out so ultrasonic cleaning won't help, the needle in the tip actually wears and the spray pattern will never be the same, new is the only solution unfortunately.

[VeeDub Geezer 0]

Nice! Now I'm proper gutted I missed those nearly new ones on eBay the other month :-(

[dannyboy 0]

i bought 4 new injectors for my mk2 gti 16v years ago and they cost me 70 euro brand new.cant imagne they cost lots more since

[VeeDub Geezer 0]

Injectors arrived today. They were about £130. just need to get around to fitting them now!