missing under boost

[jeff]

being a gti-r newbie, looking for some help here

intermittant misfire as soon as boost comes in, power drops considerably when you nail it, new plugs - leads, distributor cap and cleaned up rotor arm.

uprated airfilter and exhaust fitted, at some point i think its had a boost controller as the soleniod is loopped and the vacum hose off the air intake just afetr air fllow meter has been blanked. may be relevant . may not be??

also wallbro 225 feul pump fitted in anticipation of some other mods

any thing else i should do?

thanks

 

[Matty B]

Has it just started doing it ? Could be the air flow meter playing up. If you've got a mate with an 'R' try there AFM on your motor, thats what i did anyway when mine fooked up.

 

[GTiR-Aholic]

You say you put new leads.. are they genuine or copy? or magnecor's? (If they're copy's.. I'd try another set!)

 

[jeff]

they are 2nd hand magnecors - ive sorted out the vacum hosing as the boost solenoid had been looped and its running better, but, still intermittant misssing - altho its not nearly as bad??

dont know anyone else with an R nearby.

are they symptoms the same when the afm fucked up mate, its defo only missing under boost.

 

[saddler]

did you close the plug gaps !!

 

[gtir_pimp]

where abouts are you then? gaping the plugs shouldnt make any difference. put my new ones straight in and its fine. do you know anyone with a KV tester to test the leads?

 

[jeff]

i can see how the plugs having too big a gap could make it miss, as the boost increases the pressure inside the cylinder making it harder for the spark to jump, but i trust my mechanic to have gapped them correctly - he posts on here haha. wot should the gap be on them? and should it be closed when running increased boost?

suppose it could be poss ive got the wrong plugs - might pull one out to check

 

[saddler]

i can see how the plugs having too big a gap could make it miss, as the boost increases the pressure inside the cylinder making it harder for the spark to jump, but i trust my mechanic to have gapped them correctly - he posts on here haha. wot should the gap be on them? and should it be closed when running increased boost?

suppose it could be poss ive got the wrong plugs - might pull one out to check

my can got hesitation (missfire) under boost @1bar... try them at 0.8

 

[saddler]

where abouts are you then? gaping the plugs shouldnt make any difference. put my new ones straight in and its fine. do you know anyone with a KV tester to test the leads?

do a search of the above.. and then tell me gaping the plugs shouldnt make any difference

 

[gtir_pimp]

just saying i went to allparts, got new plugs put them in and away i went with no problems at 1bar or 1.3bar. it will obviously make a difference if the gaps to close or too far but if theyre new and not been messed with they should be ok. or are they a colder plug or something?

 

[PobodY]

Does it depend which plug you're using? Maybe it makes a big difference with iridium plugs, but not the normal kind?

 

[Matty B]

When did it start doing it ? Did you change some parts and it started doing it or was it running fine and then it started ?

 

[catchmeifyoucan01]

could be your fuel pump i had the same issue with my walbro fuel pump and that was only a week old! and that was causing it to miss -fire when hitting boost.

 

[jeff]

cheers for all the suggestions people

ill check them out over the next week, as im away until the weekend