Help Please!!!!

[STU4X4]

Hi guys. had the pulsar on the road for a week or so now and trying to iron out a hesitation/missfire but im stuck so hoping someone can throw some ideas my way .

starts first time on the button and drops to a perfect idle 900rpm once warm.
when driving its sweet right upto about 3200rpm, the boost gauge starts to rise and the second it hits full boost i get a hesitation/missfire like its holding back.

engine had a full rebuild with new gaskets,acl bearings,arp bolts etc.all other bits are standard
new thermostat
plugs ngk BKR8EIX set to 0.7mm
new fuel filter
timing set to 20` btdc
new det sensor
ive changed several other bits in an attempt to cure this which are
dist cap and arm
injectors
ign power transistor
refit factory dump valve
fuel vapour canistor blocked off
ign coil
emmisions checked (mot test and were fine)
fault code check done, showing 55 after i origonally had a det sensor fault.
lambda sensor test using check light
also as per the service repair manual ive check the voltages/outputs of
airflow meter
throttle position sensor
lambda sensor

any help would be really appreciated guys as im stuck :der:

regards

stu

 

[STU4X4]

oh and before anyone shouts at me ive used the search function on both here and the gti-r modifiers club forum which is why ive already done so much???

 

[gtir_pimp]

did you change/check the leads?

 

[Braveheart]

You have checked and changed all the obvious parts.
I would have said DET sensor but you have already changed that.
As it starts first time and idles ok, I doudt it could be bad fuel, it could be a boost leak, cracked turbo compressor housing or restriction in the exhaust system....
Keep us posted Stu and good luck!

 

[turboloon]

i know i'll get shot down for this but try unplugging the heat sensor in the exhaust..(under the drivers seat ..better off removing seat to get better acces to the plug ,it aint the one attached to the under side of the seat either,you'll see a hole in the carpet once the seat is out look in there and the line that has the braided cable unplug that...)i have had similiar probs with my pulsar spent a bloody fortune..turbo refurb..new det sensor,new lenths of silicone hosing,new plugs....i thought bugger it i'll try and unplug the above mentioned i felt i had nothing to loose and now i seem to be getting boost ok and car feels great!!

 

[mattytappy]

Had the same trouble with mine....same symptoms....its a faulty maf you have there matey...i bet ya.

 

[STU4X4]

:doh: i knew id forget to list something, yeah done the plug leads.

turboloon, whats this heat sensor ive never seen it. where does it go to in the exhaust?

mattytappy, ive been told this by a few people but when i check the voltage output as per the manual it reads ok? you still think it could be?

just to add only mods are the mongoose exhaust and decat, hks filter and a hks turbo timer. running standard boost.

as the boost reaches about 0.3 > 0.4bar its fine so normal driving is spot on, as soon as the boost goes beyond that it starts to hold back/hesitate but it does hold boost with no spiking or fluctuating.:der: :der:

 

[GTi-R23]

Did it come with the de-cat? If so the heat sensor has probably already been disconnected. All it's meant to do is bring up a warning light on the dash when the cat gets excessively hot (It bolts directly into the cat), most say it doesn't affect the engine though as it is not monitored by the ECU, hence why he said he'd get flamed for saying it might be that, still worth a look though see if anything is connected.
If you're still having probs mate, you're welcome to pop round and try my MAF on your car. My R is sitting doing nothing at the moment so it's no biggy.
Incidentally, were you in Queensferry this afternoon? Saw a Black R by B&Q which i haven't seen around before.

 

[turboloon]

i have a 'goose as well ,instead of a cat you have a middle silencer and the the heat sensor is at the back of it just looks like a 2nd lambda..like i said give it a try you ain't got nothing to loose and it will only take you 15 mins tops to do it...let me know how you get on

 

[snoon]

Could be your ecu is faulty. Although mine showed 55 after having a det sensor change, it wouldn't drive like it should until i swapped the ecu. worth trying the guys with the maf if both standard.

 

[STU4X4]

Did it come with the de-cat? If so the heat sensor has probably already been disconnected. All it's meant to do is bring up a warning light on the dash when the cat gets excessively hot (It bolts directly into the cat), most say it doesn't affect the engine though as it is not monitored by the ECU, hence why he said he'd get flamed for saying it might be that, still worth a look though see if anything is connected.
If you're still having probs mate, you're welcome to pop round and try my MAF on your car. My R is sitting doing nothing at the moment so it's no biggy.
Incidentally, were you in Queensferry this afternoon? Saw a Black R by B&Q which i haven't seen around before.

Yeah it came with the decat in it and i had a look after finding another thread about that sensor, its not got one there is a blank in its place and i cant see a sensor hanging about.

If your sure you dont mind mate that would be a god send if i could try it as im pulling my hair out over it?

Wasnt me in queensferry i had my head under the bonnet and routing through wiring loom checks on the pulsar:roll: .

 

[GTi-R23]

Only just got back today, but I'm off this thursday/friday and next weekend i'm about, so let me know when you fancy popping down. pm me and we'll sort something out.
Swapping the maf is only a 2 minute job, then at least thats something else ruled out.

 

[STU4X4]

Just Another Quick Thing Im Checking But Should I Get The Massive Release Of Pressure When I Take The Fuel Cap Off After Its Been Driven?

Stu

 

[youngsyp]

Just Another Quick Thing Im Checking But Should I Get The Massive Release Of Pressure When I Take The Fuel Cap Off After Its Been Driven?

Stu

Yes, that's normal matey.

What boost control do you have ?

Have you checked the actuator can hold stock boost ?

Although you checked the voltage at the MAF etc, did you check the resistance properties ? This will give you more accurate information than the voltage readings do.

Have you checked the base fuel pressure ?

Paul

 

[STU4X4]

Thanks, Thats One Less Thing Then?

Running Standard Controller And It Boosts Spot On To 0.7bar On A Calibrated Gauge.

Not Done The Resistance Of The Sensor I Couldnt See Any In The Manual? Where Are The Figures For It? Going To Check The Earthing Of It Again Tonight After Reading Another Post?

Not Done Fuel Pressure Check Yet, Ill Look Into That One Thanks.

Stu

 

[STU4X4]

SORTED AT LAST. THANKS TO ALL FOR THE ADVICE BUT BIG THANKS TO GTI-R23 FOR LETTING ME TRY THE MAF SENSOR OFF HIS PRIDE AND JOY ;-) .

WELL TURNED OUT TO BE THE MAF WAS JUST DIRTY, WHEN WE COMPARED THE 2 THE HOT WIRES WERE VERY BLACK AND DIRTY IN MINE. WITH NOTHING TO LOSE A GOOD SPRAY WITH SOME CARB CLEANER SAW IT NICE AND CLEAN AND THE TRIP HOME WAS A COMPLETELY DIFFERENT CAR.

MANY THANKS GARY YOUR A STAR, I OWE YOU ONE.