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Missing Under Boost?

Nishant

By Nishant,
in Engines & Forced Induction

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Nishant Apprentice

Nishant

Posted
Posted

hey all...while driving on the motorway i noticed there was an occasional miss/splutter when the car started to hit boost. And about an hour or so later when i got back onto the motorway and put my foot down on 3rd it started to miss/splutter really badly as soon as it hit boost. It eventually gets up to 11psi but with a bit of missing along the way. There seems to be a slight miss every so often when the car is idling at about 900 rpm. other then that the car drives fine when off boost. It seems to have gotten worse since it started. Initially i thought it was the coil packs so i put in the wasted spark setup i had but it still did the same.

I will put new plugs in it tmrw as i left the iridiums that it came with in it as they looked to be ok when i had pulled them out. Could be it the fuel pump dieing? Have got another ignitor pack that i can put in as well.

any suggestions welcome :P

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Nishant Apprentice

Nishant

Posted
  • Author
Posted
usual things to check

Put Copper plugs in

Coil packs

Fuel pump

Bad connections

Clean AFM

Basically the common stuff

have gone to wasted spark ( and the car actually ran better ), have got a set of copper plugs that i will be putting in it. fuel pump well am in the process of geting a Walbro 500hp pump and yeah will clean the afm tomorrow. Whats the best stuff to use to clean it anyway?

Nishant Apprentice

Nishant

Posted
  • Author
Posted

ok been playing around with the car since after wrk and heres wat ive done so far

1.cleaned the afm - no diff

2.changed the CAS - no diff

3.unplugged the O2 sensor made no diff but idle went up slightly and went back down when i plugged it back in

4.the line going from the BOV to the plenum seemed rather loose so i put a new one on with hose clamps on it

have got a set of copper plugs gapped at .7 - .8mm which i will put in tmrw

will try the other ignitor pack tmrw as well

can hear the factory pump whining away when i give it some gas ( can hear it inside as i dont have backseats in there atm.

i also noticed while driving that it builds up boost and starts missing/spluttering at about 5psi onwards which is roughly 4500rpm i think. and if i put my foot up it then it goes up to 11.5psi and it doesnt hold the boost though...any amount of boost it builds slowly goes away...like its leaking or something. and while building boost it sounds more like its leaking in surges which in return feels like its missing.

I have an external wastegate and was wondering if that could be the issue as the gasket on it seems rather naffed and i think it is leaking through the flange dats connected to the manifold. Could this be the problem??

skylinegtts Experienced

skylinegtts

Posted
Posted

ive got the same problem

i thought it was the plugs so changed them and fouled straight away that is all plugs. plugs are at 1.1 but did not miss, and nothing has changed on the car, this problem started at the drag day and two day before it was running fine. so im not sure if its the gap.

took out the coil packs and inspected them but they looked fine, although i did check the resistance and all of them were at 1.9 ohms.

mine happens when i put my foot to the floor/WOT other than that it drives fine. also i can hit 10psi on anything but WOT without any missfiring.

by the looks of it i think its the coil packs just getting too old. but not sure... if anyone can help ASAP it would be greatly appreciated need to get it fixed by next weekend.

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