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Misfire - 1.6 Turbo - After Constant 80Mph On Motorway

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misfire turbo
1K views 11 replies 6 participants last post by  zoona 
#1 ·
Have had a problem recently where if i am sat on the motorway at a constant speed ~80mph, and then i floor it i get a huge misfire (throwing my forward in my seat type misfire).

If i gradually press accelerator it seems to be ok.

It did it on the way to Mallory track day, and on the way home, but was absolutely fine on the track - only happens after sitting at a constant speed.

190whp, MS2 Enahnced ECU, Yellow top injectors. Using BKR7E-11 plugs with standard gap, but still on original (i.e. the ones on it when i bought it) leads, coilpacks etc.

Have all the kit to move to COPs, just never got round to doing it.

So my thoughts move to COPs and see what happens.

But I wanted to check if there was anything obvious (and cost free) I could try before doing that.

Any ideas?
 
#4 ·
I would try reducing the plug gap size. AFAIK an -11 is a 1.1mm gap, I would reduce it to 0.8mm.
will add it to the list of things to try, thanks.

Overboost protection kicked in?
OK, for my education... this is a figure that is set in tuner studio which if reached it will cut the spark (or fuel, depending on setup)?

It is set to 190kpa and fuel cut at the moment.

And the hysteresis is the drop in boost before it will allow the fuel/spark to kick back in again? Set to 10kpa at the moment.

I wasn't running logs at the time, but I think I need to try to recreate it and record it.

So i would be looking on the log for somewhere I hit 190kpa, and see the corresponding drop in everything until it comes alive again at 180.
 
#6 ·
Throttle position sensor.

Are you using a variable from a Mk2 or the switch type from a Mk1 ?

I have a reoccurring issue which I think is caused by this and it causes a loss off power ( no ignition). If this happened in tuned motor for a fraction of a second you would be a backfire due to unburnt fuel passing into the exhaust
 
#7 ·
Throttle position sensor.

Are you using a variable from a Mk2 or the switch type from a Mk1 ?

I have a reoccurring issue which I think is caused by this and it causes a loss off power ( no ignition). If this happened in tuned motor for a fraction of a second you would be a backfire due to unburnt fuel passing into the exhaust
will check it, but no back fire. Just missing.
 
#8 ·
It does just sound like boost cut. With it being bloody freezing outside you may find yourself hitting it quite often.
 
#10 ·
Open loop (if you are running that) and winter will do that. boost cut feels insane the first time you run into it. Like "shit, what the hell just happened, am I leaving parts on the road behind me?!"
Yup. That was the feeling...

So, excuse my ignorance, is that just cold air is more dense -> more air -> more bang -> too much bang?
 
#12 ·
more dense > higher boost (since open loop allows this, closed loop adapts) > boost cut > oh shit moment.
Its not too much bang, its too much MAP.
Yeah, sorry. I meant threat of too much bang, therefore the ecu cuts.

Thanks for replies all. Need to finish pissing about with suspension, and then get back out there, and try a few things.
 
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