Miss / Sputter Under Boost

Hi Guys,

There is a constant miss / Sputter under boost.

What could this be??? Any Settings???

Or perhaps faulty coilpacks???

Sorry, meant to add, noticed the miss on idle as well after driving about 50km to work.

Could be one of many things:
- boost leak
- spark plugs
- coil packs
- AFM

Is your car standard? Or what has been done to it?

Check for any obvious things in the engine bay such as pipe splits/disconnected pipes. Clean the AFM with carb cleaner spray, check the spark plugs and clean/replace if necessary.

mine was like that... it was the turbo... and dirty AFM~!

Thanks guys,

I have replaced plugs with a set of BCP7ES.

I have cleaned AFM with carb cleaner.

Boost is steady 0.4 bar.

I did fiddle with TPS. Could this be the cause?
Also fiddled with CAS, trying to set timing, but timing marks not visible on Crank pulley (pully damaged on edges).

Also overfuelling : dumping fuel (''mini-explosions'' in exhaust on deceleration).

Idle is at +/- 1000rpm (i picked up idle because car was cutting off intermittently (on idle only) when at stop streets.

Motor was completely rebuilt about 1000km ago.
Added a Walbro 255lph fuel pump 2 weeks ago.
t25g Turbo (off SR20DET) with t25 actuator.

Before you go any further, take the car to get it timed properly and mapped correctly, you dont want to waste the rebuild.

Also the TPS may cause issues if it's out but it all depends on how bad the missfire is.

So get it all checked properly.

Okay cool, will do.

Want to take it to Gary, but he's a bit of a distance away from me, so have to arrange to have car dropped off with him.

also check vacume lines .stock turbo is around 0.7bar boost so yours is a bit low.

Fastlane wrote:

Okay cool, will do.

Want to take it to Gary, but he's a bit of a distance away from me, so have to arrange to have car dropped off with him.

What about Poizen?

And chec your plug gaps

Had/Having the sad problem, it's my shitty UNICHIP system. Anyone know about the Spitronics system? thinking of using it.

He has my number but I'm further from gary

Caveman wrote:

Had/Having the sad problem, it's my shitty UNICHIP system. Anyone know about the Spitronics system? thinking of using it.

spitronics are XXX rather go for gotech if you have to!

Ja, Poizen is much further away.

Car did have a Dastek Unichip before the previous motor fried, but got rid of it.

I wonder if the mechanic connected all the wires back to the ecu properly?!?

I heard that std boost is 0.5 bar?!? Anyways I am using a t25g with t25 actuator. What should my boost then read?

Strangely, I have noticed that the car idles fine (actually quite smoothly) when I first start it. Only after driving it (obviously placing it under load) does it start its nonsense.

Also suspecting the eight port head having something to do with it. Maybe ''butterfly flaps'' not open enough.

What about sticky valves (or too deeply seated valves) ? What would the symptoms be?

@P3g4sus : I thought that the plugs came pre-gapped.
I didn't adjust gap, just fitted them on. Was I supposed to adjust gapping?

Those plugs are pre-gapped, but check to make sure they haven't been knocked closed or somehow wider open

Pre gap is normally 0.8 but always check

Okay, thanks. Will check gapping a.s.a.p.

Thats best If you do that, I found that 0.6 mm gap works best, had spluttering from about 4500rpm, made it 0.6 and all was fine

P3g4sus wrote:

Thats best If you do that, I found that 0.6 mm gap works best, had spluttering from about 4500rpm, made it 0.6 and all was fine

Your coils must have been shot std gap is 1.1

rat wrote:

P3g4sus wrote:

Thats best If you do that, I found that 0.6 mm gap works best, had spluttering from about 4500rpm, made it 0.6 and all was fine

Your coils must have been shot std gap is 1.1

Shot is a nice way to say it, but yes, they are over the hill, Luckily not going to go back in my car!