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holding back


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i have a j-spec tt 6spd and the last couple of days when i put my foot down its started to go then it feels like it holds back then goes agian filled it up acouple of days ago with shell optimax could it be some bad fuel?:(

 

about 3weeks ago i fully decated my sup and fitted a CW intercool its running at 1.1-1.2bar and i have not yet uprated my fuelpump could this have something to do with it? it seemed ok till the last couple of days though:search:

thanks for your help

Neil

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You need to get a better pump or at least get on a rolling road and check the AFRs throughout the rev range - could be running badly lean!!!

 

There's a misfire thread in the FAQs somewhere, that gives examples of the feelings you get, and as Jake said it could be plugs if you're still on warm plugs.

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What spark plugs are you using? How new are they? What gap are they set to?

 

 

Do you have a fuel cut defencer fitted? Any warning lights on the dash when this cut-out happens?

 

using ik24 plugs fitted 3000mile ago ruffly yes i have a fuel cut defencer fitted and there is know warning lights. doesnt do it on full boost its when you floor it starts to accelerate then holds back the accelerates agian then its gets to the second turbo kicks in and its fine.

it doesnt do it all the time noticed it 4-5 times in the last couple of days

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try doing an ecu reset and see if it clears, mine has been a bit funny possibly with duff fuel and it doesn't fully recover after, worth a shot.

 

and yes get the fuel pump done asap! and maybe a wideband o2 to be safe, think lucifer still has some left from the group buy...

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You need to get a better pump or at least get on a rolling road and check the AFRs throughout the rev range - could be running badly lean!!!

 

There's a misfire thread in the FAQs somewhere, that gives examples of the feelings you get, and as Jake said it could be plugs if you're still on warm plugs.

 

i ve just been reading the FAQ's and it this sounds like the problem i am having

 

3 - Overfuelling.

3a - mild overfuelling - You will get a drop in power. The acceleration will fall off and recover once you leave the rich spot. It kind of feels like you've hit a very strong headwind.

 

but would it be the same for funning lean?

 

is this the fuel pump i need

http://www.mkivstore.com/provisioning/eshop/index.php?target=products&product_id=1589

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Could be down to your fuel pump, as it is only at 9v until you hit 4k rpm, is it around the 4k mark that you are then OK again? Obviously the higher boost from number one with a decat could cause this problem.

 

Do you have a boost gauge? EGT gauge? AFR Gauge?

 

If not, get a boost gauge fitted, and either an EGT or AFR gauge fitted. MKIVStore are doing AEM AFRs for £169 ATM.

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yer around the 4k mark every thing seems ok, i would say its around 2500-3000rpm a feel it hold back then when the second turbo kicks in at arond 4000 it all seems ok so what you said makes sence.

 

yes i have a boost gauge fitted but no others was thinking of getting a AFR one tho so, would be a good idea to get one

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Bah why is everyone suggesting upgrade the pump? The standard pump is more than capable unless it's dodgy, and I would think there are much more likely candidates for this problem than a dodgy pump.

 

If it is running rich (still sound like plugs to me) then quite possibly knackered O2 sensor.

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wouldn't dodgy plugs give me the fault when its working hard ie when the second turbo is working?

 

Not necessarily. When I first got mine it would only do it around 4k when the second turbo came online but then be fine upper end of the rev range, swapped plugs and was fine afterwards.

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i was told you did, hmmmm glad i havent bought one now i would of been done out of £100 odd quid !!

 

http://www.stealth316.com/2-fuelpumpguide.htm

 

"The Denso fuel pump 195130-1020 (the Supra Turbo MKIV pump) is one of the best in-tank upgrade choices if you are using injectors up to 550 cc/min and are providing at least 13 volts to the pump. When 18 volts are supplied, the Supra pump is good for injectors up to 880 cc/min. At 13.5 supplied volts no other in-tank pump, except for the R33 Skyline GT-R and A'PEXi BNR32 fuel pumps, flows significantly more fuel up to 70 psi line pressure or 27 psi boost."

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Not necessarily. When I first got mine it would only do it around 4k when the second turbo came online but then be fine upper end of the rev range, swapped plugs and was fine afterwards.

 

i ll have a look at the plugs but thought irdium plugs were supose to last 10,000 odd miles and its only been the last couple of days i ve notice the holding back it was fine since de-cating.

i have been away all lasst week and not used the sup but cant think why that would of afected any thing:(

 

is there any way of testing to see if my fuel pump is worn out as it is 11years old as far as i know

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http://www.stealth316.com/2-fuelpumpguide.htm

 

"The Denso fuel pump 195130-1020 (the Supra Turbo MKIV pump) is one of the best in-tank upgrade choices if you are using injectors up to 550 cc/min and are providing at least 13 volts to the pump. When 18 volts are supplied, the Supra pump is good for injectors up to 880 cc/min. At 13.5 supplied volts no other in-tank pump, except for the R33 Skyline GT-R and A'PEXi BNR32 fuel pumps, flows significantly more fuel up to 70 psi line pressure or 27 psi boost."

 

Are you sure you are not thinking of the UK spec pump and not the J Spec which is a different part?

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