juddering on boost, what next?
 

hey again guys,

i have a 1995 sti redtop

its failed the mot on emissions so ive bought new spark plugs which i have now fitted and a new lambda sensor which i have yet to fit, may have to replace the CAT too.

my biggest problem though is that its running either very rough on boost or just cutting the power altogether when i floor it and it just then judders violently until i lift off, which i have to do almost immediately coz its so bad. its just had a service but its been doing this for a while now, really annoying me. any ideas?

ps: i am very new to scoobies so try and keep answers simple for me ta, lol

it may not have a cat fitted,hence the overboost you are feeling and why you have failed emissions , what modifications do you have? cheers bryan

the only mods as far as i know are just hks mushroom filter and turbosmart dump valve. only had the car 6 months and havent modded myself.

coil packs would be my first choice to check, were they last checked when the spark plugs were changed? (rubber boots on the end pulled off to inspect?) as even the slightest of a hair line crack and a little bit of damp weather can cause the problem you are experiencing.

also i found the same on mine, failed on emissions so took the sneeze valve off and it made it alot better as it confuse's the maf.

trying not to sound too stupid but wots a sneeze valve?

will check coil packs tmoro, thanx

agree with the above... try swapping back to the original recirc valve rather than the dump valve. Or check (or have someone check) the dumpvalve is adjusted correctly before you go spending out on un-necessary stuff. If its got a diagnostic function (check engine light) then check the fault codes by connecting the plugs under the dash and reading the 'flashes' of the light. The info is in technical archive i'm sure

sorry i meant dump valve, just a different name for people who aren't keen on them.:thumb:

thanks guys, gonna take dump valve off asap. havent got the standard one though. are they expensive? can i get an aftermarket recirc one?

I would think a fair few people on here will have one spare, rough guess at dealer price is going to be at mid to higher end of double-figures, maybe more.