Misfire or hitting fuel cut?

[boucherie]

Whenever i drive around on my higher boost setting (1.1Bar) i seem to be overshooting 1.1Bar and then the car sounds like its misfiring. this is normally around 4k rpm, however today after id checked the plugs i took it out and the boost went upto 1.25Bar. I dont think theres a fuel cut on the pulsar or could it be that my injectors are now maxing out which could cause the engine the hesistate and misfire :?:

 

[geetee]

There is no fuel cut or ignition cut as such. Personal experience of leaving the pipe off the turbo actuator once saw the engine merrily revving it's tits off and boosting way off the top of my 20psi (1.4bar?) gauge - seemed quite happy and damn quick.... but wouldn;t have for long I'm sure.

If you still have the standard boost solenoid in the loop somewhere (unlikely) if the det sensor is triggered your boost will be cut and timing retarded.... feels like the car is holding back.

Sounds like you could have one of a couple of probs...

1. Fuel starvation.... got an uprated pump yet?
2. Wrong grade / incorrectly gapped plugs....... higher boost blowing out spark?

Plenty of other things it could be but those are most common.

Cheers
Graham 8)

 

[boucherie]

ive upgraded the fuel pump with a walbro and im using NGK BKR8EIX plugs which have always been fine when using this boost setting, i was wondering if the recent spell of cold air could be a reasonable cause as this would point to more of a fuelling problem due to denser air being drawn in and if the injectors were maxing out then that would cause the hesitation and apparent misfire?
Its only done it a couple of times when i switch down to setting B (0.85Bar) and again that has been when its rather cold outside.

Ive done a fault code check and it came up all clear, so i can rule out the det sensor

 

[Dooie Pop Pop]

sounds like your sparks being blown out. maybe the gaps too big :? over the course of about 10k miles my ngk' s opened up about .04mm. bit strange your producing that much extra boost though :?

when you say its overboosting is it holding at 1.25 bar or spiking?

Stu

 

[geetee]

Standard turbo? If so - no way you'll max out the injectors at 1.1 / 1.2 bar

what else have you got wired in there? what boost controller you using?

have to say it sounds very much like what I get at under 1/3rd tank fuel..... gets to about 4k then spluters like a bitch..... lift of momentarily and go for it again it's fine. But I know that is just surge and a short pickup on the pump

 

[boucherie]

Stu - ive not done anymore than 5k on these plugs, and it appears to be holding boost at around 1.2Bar give or take a bit

Geetee - Ive got a Apexi AVCR wired in, and i currently have just under half a tank of fuel in there (normally either optimax or tesco 99), so do you reckon that it could just be a fuel surge problem :?:

 

[geetee]

Possibly fuel surge - but if it didn't happen before why now? Unless your pump has moved in the holder in tank.

I would double check the gaps on your plugs 1st to be honest.... far less work. Maybe find someone to swap em over with to see if it cures it?

Cheers
Graham 8)

 

[boucherie]

well ive gota spare set of plugs so il put them in and try again. i wouldnt have thought the pump has moved much as its got about 6 cable ties keeping it in the middle

 

[Fast Guy]

Stu - ive not done anymore than 5k on these plugs, and it appears to be holding boost at around 1.2Bar give or take a bit

On realy cold days tho, that 1.2 might change to 1.3 or 1.4

I know my 1bar has changed on a couple of realy cold days.

 

[Dooie Pop Pop]

iv hit 1.55 bar peak/spike off a 1.45 setting and i think it only stopped because iv limited it there with the boost controller :lol:

maybe your coil/ignition amplifiers tired