Boost/Fuel cut problem??
19 April 2009, 08:42 PM
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Boost/Fuel cut problem??
Hi, my pal's got a classic R plate wagon, has some sort of problem with boost and we think fuel cut?
as im led to believe, the car should run 1bar of boost, but only seems to run slightly over .5bar. when it creeps above .5bar in a higher gear at around 5K rpm, it dies on its ****, to me it feels like fuel cut, but we cant understand why if it should be running 1bar, so you'd think it would only hit fuel cut over a bar?
car is totally standard other than the cat has been removed(ish) and has a stainless 3" exhaust from the downpipe back.
we removed the standard boost control and fitted a bleed valve thinking we'd need to raise the boost with that but with it fully shut it was the same, so we slackened the actuator and now runs near enough bang on .5bar other than higher gears at 5K when it creeps above and hits the "fuel cut?"
We dont think its a missfire or anything like that, havent checked the plugs though but runs fine any other time.
Anyone any idea as to what it 'could' be, or if it IS fuel cut, and why? if we can sort that we can then raise the boost back up to 1bar (if thats what it should be at?)
cheers
as im led to believe, the car should run 1bar of boost, but only seems to run slightly over .5bar. when it creeps above .5bar in a higher gear at around 5K rpm, it dies on its ****, to me it feels like fuel cut, but we cant understand why if it should be running 1bar, so you'd think it would only hit fuel cut over a bar?
car is totally standard other than the cat has been removed(ish) and has a stainless 3" exhaust from the downpipe back.
we removed the standard boost control and fitted a bleed valve thinking we'd need to raise the boost with that but with it fully shut it was the same, so we slackened the actuator and now runs near enough bang on .5bar other than higher gears at 5K when it creeps above and hits the "fuel cut?"
We dont think its a missfire or anything like that, havent checked the plugs though but runs fine any other time.
Anyone any idea as to what it 'could' be, or if it IS fuel cut, and why? if we can sort that we can then raise the boost back up to 1bar (if thats what it should be at?)
cheers
19 April 2009, 09:19 PM
#2
Sounds like you are hitting the fuel cut which could be caused by removing the cat, as for it only running .5 bar of boost is the boost gauge working correctly, I would just plug in another gauge to see what thats boosts at. Does the car feel like its low on boost?
19 April 2009, 10:57 PM
#3
Hi, my pal's got a classic R plate wagon, has some sort of problem with boost and we think fuel cut?
as im led to believe, the car should run 1bar of boost, but only seems to run slightly over .5bar. when it creeps above .5bar in a higher gear at around 5K rpm, it dies on its ****, to me it feels like fuel cut, but we cant understand why if it should be running 1bar, so you'd think it would only hit fuel cut over a bar?
car is totally standard other than the cat has been removed(ish) and has a stainless 3" exhaust from the downpipe back.
we removed the standard boost control and fitted a bleed valve thinking we'd need to raise the boost with that but with it fully shut it was the same, so we slackened the actuator and now runs near enough bang on .5bar other than higher gears at 5K when it creeps above and hits the "fuel cut?"
We dont think its a missfire or anything like that, havent checked the plugs though but runs fine any other time.
Anyone any idea as to what it 'could' be, or if it IS fuel cut, and why? if we can sort that we can then raise the boost back up to 1bar (if thats what it should be at?)
cheers
as im led to believe, the car should run 1bar of boost, but only seems to run slightly over .5bar. when it creeps above .5bar in a higher gear at around 5K rpm, it dies on its ****, to me it feels like fuel cut, but we cant understand why if it should be running 1bar, so you'd think it would only hit fuel cut over a bar?
car is totally standard other than the cat has been removed(ish) and has a stainless 3" exhaust from the downpipe back.
we removed the standard boost control and fitted a bleed valve thinking we'd need to raise the boost with that but with it fully shut it was the same, so we slackened the actuator and now runs near enough bang on .5bar other than higher gears at 5K when it creeps above and hits the "fuel cut?"
We dont think its a missfire or anything like that, havent checked the plugs though but runs fine any other time.
Anyone any idea as to what it 'could' be, or if it IS fuel cut, and why? if we can sort that we can then raise the boost back up to 1bar (if thats what it should be at?)
cheers
What does the gauge read in 5th when it hits the 'cut'?
Is the CEL on?
Does the car rev above 5k when in neutral?
Have you got the bleed valve and other related pipework plumbed correctly?
Have you tried reading the ECU fault codes or resetting the ECU?
Last edited by Glowplug; 19 April 2009 at 11:01 PM.
20 April 2009, 12:27 AM
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thanx
hi guys this is my scoob classic that my mate is talking about the boost gauge is deffo ok, the car has been ****ed about with b4 aye got it the cel light does not light up at all so im unable to do an ecu check the car pulls ok in first and second but hits the cut around 5k in3rd 4th 5th if u go for it if u bring it in easy it easy it does rev threw 5k but u have to be easy with it, it revs ok in neutral yeah thanx for the help do my answers help u any??
Last edited by bigworm2k9; 20 April 2009 at 12:31 AM.
20 April 2009, 10:03 AM
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Defo sounds like either the gauge isn't reading correctly or the actuator is farked.
If there is no check engine and the car isn't in limp mode you won't hit fuel cut until the car makes, or thinks it's making 1.3 bar (I believe) on std ECU (std ecu runs at .7/8bar). Even with a decat the car doesn't gain .5/6 bar boost.
What does it feel like when it dies off? Fuel cut feels like you have just driven in to a wall and 100mph, it's a brutal feeling.
Explain what happens when the car "cuts"
If there is no check engine and the car isn't in limp mode you won't hit fuel cut until the car makes, or thinks it's making 1.3 bar (I believe) on std ECU (std ecu runs at .7/8bar). Even with a decat the car doesn't gain .5/6 bar boost.
What does it feel like when it dies off? Fuel cut feels like you have just driven in to a wall and 100mph, it's a brutal feeling.
Explain what happens when the car "cuts"
Last edited by Stealth; 20 April 2009 at 10:05 AM.
20 April 2009, 07:15 PM
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I've told him to get it on the rolling road to get it checked properly but he's not interested 
I'm fammiliar with the fuel cut brick wall feeling and I'd say it's deffo that, just ont understand why at just over .5bar
The car needs a looking at, CEL light, lambda sensor on downpipe doesnt seem to be connected, which we reckon is related to another problem. once the car has been run and is hot, if you turn it off and go to re-start, it will fire up, run for a second or 2 then cut out, it does this a random amount of times before it finaly starts and idles fine...as I say though we think thats to do with the lambda sensor.
I thought too that with the cat being removed, boost would raise slightly as less back pressure but we're pretty sure the guage is reading correctly so still none the wiser.
CEL light, lambda sensor...Then take it from there...
I'm fammiliar with the fuel cut brick wall feeling and I'd say it's deffo that, just ont understand why at just over .5bar
The car needs a looking at, CEL light, lambda sensor on downpipe doesnt seem to be connected, which we reckon is related to another problem. once the car has been run and is hot, if you turn it off and go to re-start, it will fire up, run for a second or 2 then cut out, it does this a random amount of times before it finaly starts and idles fine...as I say though we think thats to do with the lambda sensor.
I thought too that with the cat being removed, boost would raise slightly as less back pressure but we're pretty sure the guage is reading correctly so still none the wiser.
CEL light, lambda sensor...Then take it from there...
Last edited by vroooom ptssssh; 20 April 2009 at 07:18 PM.
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20 April 2009, 10:28 PM
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thanx again guys
thanx again guys for ur help im gona check out the cel light prob in work go on from there hopefully get some answers my mate vroomm ptssssh has also said about the none start when hot fault thats a pain in the *** hole
Last edited by bigworm2k9; 20 April 2009 at 10:31 PM.
21 April 2009, 12:57 AM
#9
The lambda sensor is located in the drivers side exhaust manifold, the sensor in the downpipe is the 'cat on fire' or 'exhaust gas temp sensor', if the car has a decat exhaust then the sensor in the d/p is obsolete as you have no cat to melt, mine is fully removed and blanked, no probs
Restart problem could be the 'coolant temp sensor' on the way out
As i said before, get the CEL working, its there to help you find the faults
Restart problem could be the 'coolant temp sensor' on the way out
As i said before, get the CEL working, its there to help you find the faults
09 May 2009, 12:45 AM
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well peeps the latest on my scoob is that iv'e changed the spark plugs and the ect sensor and also done an ecu check which came up with no fault codes
the car is still running the same hitting the boost/fuel cut at 5k in 3rd 4th and 5th
im about to buy a 3" downpipe as the origional ****ed cut up and de-cated one is blowing and corroded im jst not sure where to go next with it *** its still running the same any ideas
09 May 2009, 10:35 AM
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If it happens at 5k then it doesnt sound like boost spiking/fuel cut to me. When i put my 3" downpipe on mine i got boost spikes/ fuel cut at 3-3.5k ( when full boost starts ? ) Unless you've got some crazy turbo where you only get full boost pressure @ 5k ?
10 May 2009, 03:10 AM
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**** knows mate its doin ma head rite in dont know any history of the car b4 i had it but turbo looks standard car goes well 1st and 2nd but say for instance im trying to race someone and i go for it as soon as it hts 5k its like hitting a brick wall no revs and now power soon as it drops to 4ish it comes back and u can take it past 5 if u bring it in slowly u could probably red line it buut if u drop a gear and go for it soon as u hit 5 again the brick wall jumps out the road and shouts halt u mother forker 
dont know any history of the car b4 i had it but turbo looks standard car goes well 1st and 2nd but say for instance im trying to race someone and i go for it as soon as it hts 5k its like hitting a brick wall no revs and now power soon as it drops to 4ish it comes back and u can take it past 5 if u bring it in slowly u could probably red line it buut if u drop a gear and go for it soon as u hit 5 again the brick wall jumps out the road and shouts halt u mother forker
Last edited by bigworm2k9; 10 May 2009 at 03:12 AM.
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