Dropping revs when changing gear/engaging clutch and long ''hissing'' noise

paz

Active Member
Hi all,

Following on from my earlier thread about a boost leak, I checked over the car and could track down any problems. I then drove the car for a couple of 30 mile round trips and had no problems (apart from a different ''dump'' noise when changing gear).

However, last night I noticed that the car is running slightly rough (nothing massively noticeable, just a slightly rough idle and minimal 0-4 knock readings on the SAFC-II) and when I change gear, the revs seem to be dropping quicker than normal, down to about 700rpm and then the engine catches itelf and revs before stalling. To be specific it has never stalled or come particularly close, it just sounds like it would if the revs continuesd to drop at that speed.

At the same time when changing gear at even extremely low boost (i.e. accelerating to 2000-3000rpm and the changing up) I'm getting a long hissing noise from the passenger footwell - by long I mean approximately 2-3 seconds or until I engage the next gear).

So, I'm not sure what this is - do the problems being intermittent seem to sway away from a boost leak or dodgy MAF? The one thing I was wondering with the particularly long 'hiss' noise when chaning gear is could my BOV be leaking? Has anyone experienced anything like this before?

Cheers

Paz
 

gtir_pimp

New Member
dump valve could be the problem. i have a hks ssqv and a mate had a spare bailey dump valve lying around so we fitted it to my car to see if it still worked and every time i changed gear or revved the engine whilest still the revs dropped to around 500rpm after the dump valve hisssssed. it was like it shut off too far. and my old hks dump valves sound changed so replaced it. think it was leaking as my car was a bit down on power.
try swapping it for a known good one and if you cant find one then bung the pipe the valve comes from and blank off the vac pipe to it
 
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paz

Active Member
So do people think I should look at the DV first, or should I start somewhere else - is there anything logical to tracking problems of this type?

Cheers
 
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