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Boost or fuel issue?

Havoc

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Right guys, car is driving a bit funny and I don't know what to put it down to...

Basically 2 faults and not sure if there connected or not as quite a bit of work has been done to the car,

1st of whilst accelerating hard and taking the revs through the range at high rpm in low gears it feels a bit like the car is softly hitting the rev limiter befor it even has hit the rev limiter, carets on revving till it then does hit the actual rev limiter... Any thoughts on this? I initial thought it would be the airflow meter, Iv tried cleaning it and fitting a different one but still does the same.. Any ideas??

Second fault is that when your in 5th and 6th gear driving at speed and accelerate it boosts up fine but seems when you hit peak boost it loses all power, peaks again and the loses it again repeatedly ubtill you come off the power and then it drives fine again....

Any thoughts on this as I'm stumped as the car seems to boost fine but also drives fine in a regular pace....

Any help would be spiffing cheers!
 
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I had similar issue with my S15 and i ended up taking it to horesham developments and it was diagnosed as the knock sensor!! Maybe worth looking into!
 

Havoc

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I had similar issue with my S15 and i ended up taking it to horesham developments and it was diagnosed as the knock sensor!! Maybe worth looking into!
Ouch... Ill keep that in mind if I can't fix it, thanks.
 

DeanS15

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If you're not running too much boost for the setup and it was previously fine on your setup then first thing I'd check is the plugs. If you are running no dump valve or an atmospheric valve then the car will overfuel on the lift off, this can foul them up and affect thier ability to spark under heavy loads. Like you say if you can drive through it when building boost steadily but it stutters like it's hitting a limiter when you gun it then it's definitely worth checking them. What boost you running on what setup? It will only cost you a few quid to throw a set of the right coppers in with the right gap for your tune, I know iridiums are meant to be great but I had fouling problems with them, even on a well set up car, when I fitted coppers on the right gap my missing issues went away. Also a coil pack on it's way out or a small boost leak can do the same, there are a few things that will throw up similar symptoms to what you have it's just a case of checking each one and eliminating them ;)
 

Havoc

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If you're not running too much boost for the setup and it was previously fine on your setup then first thing I'd check is the plugs. If you are running no dump valve or an atmospheric valve then the car will overfuel on the lift off, this can foul them up and affect thier ability to spark under heavy loads. Like you say if you can drive through it when building boost steadily but it stutters like it's hitting a limiter when you gun it then it's definitely worth checking them. What boost you running on what setup? It will only cost you a few quid to throw a set of the right coppers in with the right gap for your tune, I know iridiums are meant to be great but I had fouling problems with them, even on a well set up car, when I fitted coppers on the right gap my missing issues went away. Also a coil pack on it's way out or a small boost leak can do the same, there are a few things that will throw up similar symptoms to what you have it's just a case of checking each one and eliminating them ;)
Nice one cheers for that, Iv literally only had the spark plugs for a month there iridium cold 7's and there fine although they where heavily fowled up, so I cleaned them up and now the car is even worse?? and now has the boost issue in all the lower gears aswell :S I've always used the same plugs and never really had a problem befor...

Iv tried checking all boost pipe and flow connections and all seem fine but guess I'm going to have to pull them all of again and make double sure...
 

DeanS15

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That's what I had problems with, ngkbkr7. I cleaned them up an the problem would go, then come back and after a couple of clean ups, the only thing that got rid of it was a new set of plugs....
 

Havoc

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That's what I had problems with, ngkbkr7. I cleaned them up an the problem would go, then come back and after a couple of clean ups, the only thing that got rid of it was a new set of plugs....
Fair enough, would like to eliminate the plugs from the equation so how do I go about finding out what 'coppers' to use or look for fella?
 

DeanS15

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If you're running grade 7's then just throw in some ngk bcr7es gapped at about 0.7mm should work, and for grade 8's bcr8es. It's about 6 quid for four so worth doing to rule out ;) best of luck with finding it
 

Havoc

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Just put a brand new set of iridium spark plugs in... And cleaned airflow meter.... Still doing the same...
Starting to think its something more sinister... Going to take all the boost pipes of Tomorow double check everything and get some better hose clips...

Anyone think this could be a fuelling issue?

If none of this works ill get the knock sensor looked into... Anyone no what that jobs like or price wise to fix/check??
 
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Just put a brand new set of iridium spark plugs in... And cleaned airflow meter.... Still doing the same...
Starting to think its something more sinister... Going to take all the boost pipes of Tomorow double check everything and get some better hose clips...

Anyone think this could be a fuelling issue?

If none of this works ill get the knock sensor looked into... Anyone no what that jobs like or price wise to fix/check??
The problem with my car was the same and felt like it was misfiring all the time... I tried everything from plugs, to air flow meter, tested for boost leaks and like i said,it was the knock sensor!!! It drove me crazy trying to sort it! Dave t's problem was the knock sensor loom I think. It's a pain to get to as right under inlet manifold.
 
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