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misfire/spluttering HELP

3K views 54 replies 9 participants last post by  badger33 
#1 ·
BIT OF HELP NEEDED,CAR HAS DEVELOPED A MISFIRE WHEN BOOST IS TURNED UP,STARTS AND RUNS FINE NO PROBLEM ON STANDARD BOOST AND WILL ACCELERATE NO PROBLEM AS LONG AS BOOST IS NOT INCREASED,BOOST CONTROLLER IS A SPEC S BLITZ AND APPEARS TO BE WORKING OK,WITH CONTROLLER ON 0 SET AS SAID THE CAR WILL RUN FINE BUT AS YOU TRY TOM INCREASE BOOST WILL START TO SPLUTTER QUITE BED AND GETS WORSE THE MORE THE BOOST IS INCREASED,MAX IS SET @.85 ,BUT IT STARTS TO PLAY UP WAY BEFORE THAT,DID HAVE AN AFM ISSUE A WHILE BACK AND SEEMS TO BE LIKE IT SINCE CHANGING IT,BUT HAVING SAID THAT THE CAR WAS TINKERED WITH BY TUNING CO IN PLYMOUTH BECAUSE OF ROUGH IDLING BY PREVIOUS OWNER WHICH TURNED OUT TO BE THE AFM WHICH FAILED SOON AFTER I PURCHASED THE CAR,AND SINCE FITTING HAS SORTED THE IDLING ISSUE,ANY IDEAS WOULD BE MUCH APPRECIATED,
 
#2 ·
Fit some new plugs and gap them to 0.8mm if that doesn't cure it then it could be coil pack/s.
 
#6 ·
Wont be the MAF if it runs OK off boost, what plugs are you using? coil packs will normally show up lower down but first signs can be limited to boost as the spark is under more pressure during boost.
 
#11 · (Edited)
But why only at higher boost?Sorry to sound a bit negative but why will it run fine and accelerate flat out without a murmer on low boost but start to splutter and get worse the more the boost is increased,its not an occasional or random mis either more like a rapid bbrrrrrrppppp lol bear with me cause its doing my nut in
 
#14 ·
not acurately no but the stock gauge used to go to around 3/4 way up fine but now wont run at that level or at least starts playing up well before that,the boost gauge is set at 3 levels i think its 0.4 0.6 and 0.8 but did have spiking issues previously where it would reach 1.0 bar ,and yes its a stock ecu.
 
#21 ·
The standard ecu doesn't monitor the boost level. It does however monitor the afm signal, which will show higher airflow if the boost is higher. The standard afm can just about handle about 0.85 bar of boost from the standard turbo, provided it's not faulty. But without a proper boost gauge, there's no way of knowing what pressure it's actually running at.
 
#22 · (Edited)
if the miss fire is more of a back fire or engine judder , then it could be the Stock ECU and FCD ( Fuel cut defender ) causing issues . You need 43psi fuel pressure and either a FCD fitted or ECU tuned . If not the engine will lean out and BLOW UP - this is not an exaggeration !!!!!!!!!!!

If you have not wired in the boost controller into the ECU loom and fooled FCD in ECU - then you MAY/WILL blow a ring journal !

Turn boost down as you need more than just boost pressure- to go faster
 
#27 ·
Understand what your. Saying mate and totally agree just can't understand why it went to crap all of a sudden at the end of the day I always got my 8year old daughter with me so setting lap records ain't my thing,she's the reason I sold it in the first place8. 1/2 years ago and traced it down last September and bought it back,,,
 
#23 ·
Tks Stuart - thought the sensor was wired to the ecu as well. It's been a long time since last i had a look at the pinouts but just had a refresh. Makes perfectly sense of how other stuff is connected.
But lets continue from there then. Worth having a look at the ecu fault codes if it shows any that is.
 
#26 ·
Yes but can't find it or see where it would have been added to the loom,strange thing is when I took it to the guy that had fitted it he couldn't find it either but its clearly on the invoice that the previous owner had paid for ,the tuner didn't recognise the car or make comment that it he'd been fitted,he to looked by the ecu and its not there surprising since he FITTED it''''':dogpile:
 
#29 ·
No I haven't just a bit lost at the moment mate could it cause this problem I have ,,,bought it off egay after my other one packed in the car died out and after disconnecting it it started up got the replacement put it on and it started fine but has left me with this problem
 
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