hesitation when first coming on boost

[sambb]

Hi all,

I have a bit of an issue where the car is sort of pausing/hesitating when first boosting. Its only realy apparent in 3rd gear eg especially if I'm rolling along in 4th and knock it down to 3rd prior to going up an incline - when I first transition from driving along normally to getting on the accelerator reasonably hard at about 3000rpm the car will hesitate. Its not as distinctive and stammering as a misfire usually is. Its not lag because it is spooling but feels like something is interfering with the boosting.Once it gets into stride though it'll pull hard.

I assume its not pulling timing because the revs are there to begin with, the car has plenty of road speed (about 70ish) and this is just in the course of normal commuting - happens the same if its 17 degrees ambient or 30. Changed to different 98ron and ran fuel cleaner through it (it has a new fuel filter recently). As it was after that transition from vac to boost I changed back to stock from my turbosmart Kompact plumback DV with no joy.
I had thought plugs so changed from BKR7E's to PFR7Q's for no joy either. I had noticed however that on cylinders 1 & 4 that those plugs had a marking on the top of the insulator that looked like they'd been 'smudged' with the tip of a grey/black texta. Is that indicative of something sinister?

Was going to try a different N75 next. Any ideas?

thanks

Engine is otherwise stock except for stage 1.

[h100vw]

Hi all,

I have a bit of an issue where the car is sort of pausing/hesitating when first boosting. Its only realy apparent in 3rd gear eg especially if I'm rolling along in 4th and knock it down to 3rd prior to going up an incline - when I first transition from driving along normally to getting on the accelerator reasonably hard at about 3000rpm the car will hesitate. Its not as distinctive and stammering as a misfire usually is. Its not lag because it is spooling but feels like something is interfering with the boosting.Once it gets into stride though it'll pull hard.

I assume its not pulling timing because the revs are there to begin with, the car has plenty of road speed (about 70ish) and this is just in the course of normal commuting - happens the same if its 17 degrees ambient or 30. Changed to different 98ron and ran fuel cleaner through it (it has a new fuel filter recently). As it was after that transition from vac to boost I changed back to stock from my turbosmart Kompact plumback DV with no joy.
I had thought plugs so changed from BKR7E's to PFR7Q's for no joy either. I had noticed however that on cylinders 1 & 4 that those plugs had a marking on the top of the insulator that looked like they'd been 'smudged' with the tip of a grey/black texta. Is that indicative of something sinister?

Was going to try a different N75 next. Any ideas?

thanks

Engine is otherwise stock except for stage 1.

Sam, don't speculate. Do some logs and I am sure you'll find out the cause. How big was the gap on the BKR7Es 28 to 30 thou is optimum in my experience.

Gavin

[sambb]

28 thou for the BKR's and now the out of the box gap for the PFR's. Yeah I know - i'll have to track down someone with VCDS and do logs now that a few easy things have been checked.

[noone]

ECU flashed?

[sambb]

yep. Phase 1 CC.

[noone]

Log

Could be boost leak, or one of many little things

[sambb]

Well the hesitation is still there. I bypassed the n249/VAC thinking that it may have been causing the DV to bleed slightly. Surprised at the difference that made in general but it had no effect on the hesitation.
I got my hands on a v-checker and was surprised to see no codes at all - and no cylinder misfire errors. Was starting to think it was that since 2 of my plugs were discoloured and the idle can be pretty rough sometimes too. How bad does a coilpack have to be before it codes?

[noone]

Could be a boost leak if no codes. Worth going over all the piping and connections from the turbo to the intake. Check Silicone for splits

[h100vw]

Well the hesitation is still there. I bypassed the n249/VAC thinking that it may have been causing the DV to bleed slightly. Surprised at the difference that made in general but it had no effect on the hesitation.
I got my hands on a v-checker and was surprised to see no codes at all - and no cylinder misfire errors. Was starting to think it was that since 2 of my plugs were discoloured and the idle can be pretty rough sometimes too. How bad does a coilpack have to be before it codes?

I have seen massive misfires in a TT and it wasn't throwing codes, so you can't rely on the ECU to see everything. I don't think there's a tool that compares to VCDS for this kind of thing, unless you spend a lot more money.

Gavin