Hi guys. Was at the dyno place yesterday finally getting the car tuned but got a problem.

 

In short the car runs spot on until I go on boost at which time it misfires. I went through pulling off the coil pack connectors to see if any of these were down and it appears number 4 wasn't making any difference.

 

I've tried another coil pack and also tried changing a couple round, the plugs were brand new but still no change when I pull the plug off.

 

Any ideas what this could be or how I can check??? I have datascan if that helps.

Maybe PTU perhaps? This is. Series 1 ptu.

Injector plug connections green ?

boost blowing plug out decrease the gap maybe.

If its OK off boost but not sparking on boost then suggests that you have a spark, just not strong enough to jump the gap at high chamber pressure.

 

As taff said, try gapping the plugs down to 0.8 - 0.6mm. Its odd that its only one plug though. Check all the wiring and connectors are good to that coilpack and that all the PTC connections are clean. Would have thought it unlikely to be the PTU its self as its OK off boost and its more or less just a switch.

Did you try changing the spark plugs around? Could just be a bad plug.

 

Best bet is if you can find someone with an oscilloscope and actually scope the coil and see what's happening.

I will try changing the plugs around when it spots raining lol. the gap was set at 0.6mm when we put em in.

 

I will check whether the connectors are green too but its doubtful as the whole loom is only about a year old.

 

I could be wrong about it only being the one plug I guess. Thats coming from the fact there no change on the engine when I pull the plug off on that plug where there's a difference on the others.

Have you tried idling the engine and carefully wiggling the connector wirring to that coil pack to see if it comes alive? I had a similar problem that got cured this way and touch wood has stayed cured. I never did identify exactly where the bad connection was but it affected middle cylinder LHS when facing the engine.

I will try changing the plugs around when it spots raining lol. the gap was set at 0.6mm when we put em in.

 

I will check whether the connectors are green too but its doubtful as the whole loom is only about a year old.

 

I could be wrong about it only being the one plug I guess. Thats coming from the fact there no change on the engine when I pull the plug off on that plug where there's a difference on the others.

 

then it's not running sweetly off boost if that's the case....

 

is that cylinder getting fuel ie is it definately a spark issue?

then it's not running sweetly off boost if that's the case....

 

is that cylinder getting fuel ie is it definately a spark issue?

 

I'm not sure. Aarrrggh how do I check???

you'll need to check if the spark plug is getting wet.

Whaat plugs did you fit in the end and did you fit them yourself?

smithy

Don't want to hijack your thread but I'm having the same trouble with a stock engine on my no 1 cylinder. I've done all the checks as well, including changing the spark plug but still not working :sneaky2:

 

So I would like to know possible other causes of this.

you'll need to check if the spark plug is getting wet.

 

Sorry to sound really thick Jaffa but how do I check or do I just pull it out and it'll be wet?

 

Smithy, the garage put em in but they were heat rating 7 as no 8s available - they're on order though.

Sorry to sound really thick Jaffa but how do I check or do I just pull it out and it'll be wet?

 

Smithy, the garage put em in but they were heat rating 7 as no 8s available - they're on order though.

 

Take the plug out and look at it, if the cylinder hasn't been firing but fuel is getting through then the plug will be soaked in fuel and will smell of it as well.

That makes sense.

I will have a look as soon as it's dry