OK guys, I think this co-incides with the cold weather, but on cold start-up my vaccum is only reading around -10 psi, and then slowly goes to -18/-20 after a few minutes of idling.. (where it always used to be)

 

If I start to drive it when it's like that it's very lumpy :(

 

I've hunted around the engine but can't find any leaks when it happens - so any ideas?

 

I've already got a new coolant sensor which I'm putting on in the morning, so I'll see if that helps.

You are lucky to find any vacume leaks by just listening.

 

I thought the cold air means the vacume will be lower because the air is more dence. Or is that the wrong way round,.

Hi Jaffa

 

I have been seeing this too, but it does indeed return to the left after 10 minutes. The car still runs fine from cold though.

 

You have a -20 on your guage?

 

Mine is -14 to +14 psi (uk car). Normal vaccum is between -10 and -14 but currently -7 to -10 in very cold weather.

 

perhaps the cold is playing havoc with the rubber hoses causing them to contract (much the same as fuel hoses do occassionally per earlier threads) leading to vacuum leaks?

 

Richard:confused:

I was thinking along the same lines re vacuum hoses, will start over-hauling them soon.

 

PS aftermarket boost-gauge :D

Hmm. Could be a problem with loose pipes when cold, then expanding and sealing the leak?

 

Mine reads -18 or 19 from startup.

 

(Aftermarket gauge as well.)

I think this is completely normal. The ecu lets in a bigger richer mixture when stone cold. It takes time to lean off to a normal vacuum on tickover.