vacuum leak?

[gotham.r]

hey guys,

on the weekend I decided to clean out my plenum and throttle body as well as install the mace 25mm MI and 12mm PS. my car is a vx s1 v6 ecotec

had no problems with the install part, went quite smoothly but after I started the car it was running an alternating rough idle and making a hissing noise like there's a vacuum leak.. I've checked over the seals/gaskets with some soapy water and can't seem to find anything..

it seems to be running rich and churning through petrol like no tomorrow, a friend and even Steve told me that it can take a week for the car to reprogram the ecu but I'm not sure if this is correct?
any help is appreciated

 

[cander24]

Your symptoms and the fact you have a 'hissing' noise would suggest a vacuum leak. Have you also checked the vacuum lines to the throttle body and rear of the plenum?
Any pcm trimming/learning should happen fairly quickly.

 

[gotham.r]

yeah that's what I was thinking but I've checked over all the lines and the seals so I'm not sure what else to do other than redo it all..

 

[Deltak]

If it is a vacuum leak, soapy water doesn't help as the vacuum sucks it in!

What you need is, with the car idling, carelfully spray some WD40 or similar at suspect joints. The one thats leaking will cause the engine to race for a short time.

Hope this helps.

 

[gotham.r]

thought about that, was insure as it's flammable? but I'll give it a try, would it be worth looking for some high temp silicone and going around the edges?

 

[gotham.r]

found the leak then, would it be worth re-sealing the whole thing or is it possible to get some sort of high temp silicone and go around the edges?

 

[Brett_jjj]

Id be taking it apart and refitting the gaskets and spacer etc again properly as they shouldnt leak at all when correctly fitted, somethings not quite right there somewhere..

 

[gotham.r]

had another look over it again turns out one of the bolt holes In the plenum had cracked creating a massive hole for a vacuum leak.. so that was my problem, obtained a brand new plenum and throttle body and reassembled it all without the manifold spacer and is now running even better than before the problem so thanks for all your help

 

[havavb]

Hey guys rather then make a new thread about something that's been brought up about a million times, id just post in one already, I know I have a vacuum leak, it was staying on demister and would change after I fiddled around with the knob for some time (vt s pac non climate control btw). Basically it didn't bother me too much. But now the air is venting out from my footwells on demister (which is a pain in the backside) as today wet weather window began fogging up. turned the heater on (1) whilst on demister, could feel it at my feet so fiddled with the knob to switch positions, which it would change sometimes. So I cranked it upto max so it was easier for me to determine where the air was following from and it changed perfectly on max (I think 3 or 4?). Which I turned it back down to 1-2 and boom back at my feet. So basically I know where im looking at the hoses behind the intake (I will be looking tomorrow morning rain hail or shine lol). But my questions are: a) is there an easy way to determine where the leak is by visual inspection or should I have the car running? b) if the problem doesn't lie in the engine bay, it would be under the dash id assume? or even the heater control panel?

 

[djwatson93]

**** just done a plenum spacer myself 2 month laters just got this vaccum leak hope mines not cracked -.- just got rid of the spare parts car