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spluttering 944 turbo

u63af

u63af

New member
I already had a post about a year ago about this problem with my car but it has been off the road since then. Basically when the car is under full boost and full throttle it seems to hesitate and splutter, if you back off the throttle to mid way then it seems to pull better and not hesitate. I have changed air flow meter, tps is clicking when you move the butterfly. It had new plugs that were a grade colder and new leads. Anyone got any ideas?

When I first got the new leads (before problem started) they were shorting out against the water pipe. I revealec that the rubber cover that goes over the plug had moved allowing the metal to spark, I but the rubber over this again. Could it be that I have a duff set of plugs and this may be the problem?
 
I am going to be running about 18 psi so thought it was safer to run colder plugs. Was this the wrong move?
 
I know you've been looking at the electrical side of things. Have you checked the output of the fuel pump ?

If your fuel pump and/or filters are suspect/ blocked you'll get a very similar symptom to the one you've described - hesitation under full load when max petrol is required.

I have a similar issue a couple of years ago at Silverstone -the pump was on it's way out and I replaced the pump and the external canister filter.

The turbo's and I suspect S2's have a conical purolator filter within the tank which acts as a primary filter prior to filtration after the pump.

It might be worth having your fuel pressure checked at the fuel rail, should be ~ 2.5bar under full boost
 
I think it shoud be 2.5 or 3 Bar, whatever pressure the reg you have is supposed to be, plus boost pressure. I think the fuel rail pressure has to be 2.5 Bar above the manifold pressure.
 
How do you get to the in tank filter? I was originally thinking it might be fuel pump a while ago or injectors. I have since bought 55lb injectors but not changed fuel pump. Where is the best place to get a fuel pressure gauge?
 
Now you mention the change to uprated injectors, it's best you replace the pump anyway !

Ref. the pressure gauge, you can buy an in-situ one from Andrew at Promax or unscrew the cap at the end of the fuel rail (don't loose the ball bearing...) and take it to a Pirtek or hydraulics firm and have them make you one up with a suitable fitment/braided hose to a Bar/PSI gauge.

The in tank filter is quite staightforward to get to.

Looking up a the car, the fuel tank has a large metal strap (~ 2 inch wide) across it. Undo the bolt holding it to the chassis at one end.

As this comes away, the plastic shield that houses the fuel pump and the flexible rubber hoses will be exposed.

Within this, you'll see the main feed from the fuel tank which is on the side of the 'bowel' or lowest collection point of the tank. IIRC, after you've drained the tank and removed the various pipes, it simply screws into the plastic tank.
 
Sounds to me like its just blowing out the spark under boost. Your spark is probably too weak to run those plugs either because something is worn (coil, distributor etc) or those plugs are too severe and are not igniting the fuel with the spark they are giving. Most cars run individual coil packs now so performance plugs are probably designed to suit. I would try a set of standard plugs first and then investigate further.
 
Boost leak ? , mine cut out under boost and it had a boost leak therefore under boost/full throttle it overfuelled and cut out until you took your foot off the accelerator. Doesnt sound that different to his problem.

Regards Mas
 
I was going to suggest boost leak. Sounds like you're overfuelling - you can check by taking it for a test driver where you drive frequently at the stage where it spluttering - i.e. at WOT. As soon as you get home and when the engine has cooled check your spark plugs. If there are thick sooty deposits on the spark plugs then you are either over fuelling or you're not getting combustion).
 
Worth getting a wideband gauge. Ideal at times like this as you can tell immediately if fuelling is the problem.
 
Mine was doing this but it was being stored over winter with the occasional warm up run out, fuel was low, when i brought it out to put back on the road i stuck in half a tank of fuel, problem gone job done !
 
ORIGINAL: Frenchy

Mine was doing this but it was being stored over winter with the occasional warm up run out, fuel was low, when i brought it out to put back on the road i stuck in half a tank of fuel, problem gone job done !
Click to expand...

yes thats how I got problems twice last year . Both times I shut the car off with a very low tank and it then refused to start . I think the tank needs a minimum amount of fuel but I'm not sure why it will run happily to empty but not restart
 
Sorted out the car, there was a small crack in a hose that comes off the rubber hose in between the turbo and air flow meter.

Cheers for all the help guys. I might replace my fuel pump anyway, probably a bosch 044
 
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