3B Misfire & Boost Cut

[vagrallye]

hi guys a little advice please on a misfiring 3b s2
mrc chipped 1.3bar

no fault codes on blink or diagnostics

got an intermitted misfires on more than 1 cylinder under load sometimes sounds like all 5 other times just one or 2
i dont know weather its pressure dependant but does it more under more load/boost, say half to full throttle , ive seen almost a bar just under fiull throttle and it doesnt do it , and sometimes under a bar on wot and it will do it , or visa versa! so there is no specific time it does it
cap and arm are good gonna try another set of plugs tomorrow just in case, and i have a new set of leads on order as the old ones have gone a little hard
wiring up my inovate wideband also tomorrow to make sure its not fuel orrientated
just fitted a new coolant sensor on the back of the head tonight but have not drove it since.
will see what happens tomorrow and ill check afr

any ideas?

[Acidburn]

On my 3b it was the leads, especially the lead to the coil pack, that got trapped in between the strut brace and pipe work and resulted in mis-fires and some flames

i'd go for either problem with leads or maybe a boost leak but most likely leads.

[vagrallye]

On my 3b it was the leads, especially the lead to the coil pack, that got trapped in between the strut brace and pipe work and resulted in mis-fires and some flames

i'd go for either problem with leads or maybe a boost leak but most likely leads.

i have a set of leads on order should arrive monday ill try them

[vagrallye]

in my other topic im asking about factory wastegate settings and someone has replied talking about the boost coming in to strong and the ecu not being able to deal with it, could this be the same sort of problem? along with perhaps old leads?

This is the quote from my "boost" topic
"Proper wastegates do NOT have bolts with nuts sticking out of the middle of them. They have a hex (Allen) socket-headed bolt that sits down IN the wastegate. Stock has the top of the socket-headed bolt down about 3 or 4 threads IIRC.

I am running a 1.9 bar WG spring and have to have the socket-headed bolt run right to the top because otherwise the rate of boost rise is too much for the ECU and it thinks it is overboosting and goes into a reduce boost/increase boost jerk/coughing session."

could thislast part have something to do with it?

[newsh]

If its a heavy missfire, car starts to boost then pretty much cuts out, making it lurch, it could be a boost leak or the MAF connector. Do a search for maf connector and Maf cutout, you need to clean it carefully and make sure its mating properly. Leads will give you a flat sort of miss, power drops off but engine keeps going.

[newsh]

Here you go.. Stock Wastegate Spring

[vagrallye]

thanks newsh

looking more to be leads but i do think it makes boost a bit too agressively so ill check my spring
also had a wierd thing happen a couple of times yesterday...
just driving along , everything in one position ie throttle ,revs speed etc and it was like the ignition live to the engine was cut for about a second then reconnected?
wasnt long enough for anything to happen ie loss of power, speed or revs
wierd.. any ideas
ps it done it in day light and night , when it done it at night there was no change to the interior or exterior lighting so it couldnt of been an " overall" electrical problem

may be these could be related of two seperate problems

[Davidsinclair05]

sounds like the boost pipes to me, i had a problem like this the pipe was perished at the back of the engine (behind the battery)and every time i floored it the car would lurch forward and jump about, sounded like a cylinder misfiring lots of black smoke and the car would go in to limp mode where it wouldn't let you rev over 2500rpm ish. I got a diagram from either the forum or on S2central for the layout of the boost pipes.

[vagrallye]

sounds like the boost pipes to me, i had a problem like this the pipe was perished at the back of the engine (behind the battery)and every time i floored it the car would lurch forward and jump about, sounded like a cylinder misfiring lots of black smoke and the car would go in to limp mode where it wouldn't let you rev over 2500rpm ish. I got a diagram from either the forum or on S2central for the layout of the boost pipes.

doesnt lurch or jump about and it doesnt go into any form of limp mode
ive checked all vacume pipes off the inlet manifold, ill check the ones from n75valve

[vagrallye]

just been out for a quick blast it seems to be misfiring on full boost or wot , if i hold it at 1bar it doesnt seem to do it, im thinking more of a wot problem than boost tho cause it done it on the old chip and that only ran 10psi , on the old chip it was fine to about 7psi and then full boost + full throttle it misfired slightly
the problem is not there all the time tho.
the problem was "less apparent" on the old chip lol
i did notice the coating of one of the knock sensors was peeling slightly...
i managed to get my wideband afr guage in and the fuel is ok if you hold it through the misfire it does seem to dissapear

[newsh]

When mine was doing this it was leads, the spark has a harder time at higher boost.

[vagrallye]

When mine was doing this it was leads, the spark has a harder time at higher boost.

yea i hope it is

[newsh]

Make sure you don't have a small leak on the boost/vac pipe to the ecu or to the boost gauge if its Tee'd off the same line.

[newsh]

Where the vac line connects to the ECU see if you can twist the connection, sometimes the clip can be done up tight but not clamp the tube properly and it leaks. Causes all sorts of problems

[vagrallye]

Where the vac line connects to the ECU see if you can twist the connection, sometimes the clip can be done up tight but not clamp the tube properly and it leaks. Causes all sorts of problems

will check this