lionelw350

Driving a boosted 99 civic ex. I'm thinking i have a vacuum leak some where as my boost gauge reads -10/-11 at idle and i am pretty sure thats not right. Anyone know of a common sport where there would be a leak. My AFR is also lean on initial start up and under full throttle. Not sure if thats related or not.

Could it also be that there is a sensor or something that needs to be replaced? Any help is appreciated, thanks in advance.

john0270

Your wideband o2 doesn't measure accuratly for 10-30seconds or more untill its good and warm so that could be that issue, does it stumble or miss on cold startup? If you don't have any fuel management your going to be lean at wot. Not timed correctly can make lower vac also

lionelw350

No it doesn't stumble or miss on start up. I have it going in to the dealer on monday so i will tell them to check the timing as well. I have done a few vacuum tests must self and haven't come up with anything so maybe the timing is out.

lionelw350

So took my car to the dealer and they couldn't/didn't find any vacuum leaks. He told me that he thinks my rings are shot, however i did a leak down tests and got 1%,4%,5% and 7% in each cylinder nothing that would indicate a worn out engine.

I also asked if my timing could be off but the mechanic said that it was fine.

Anyone got any other suggestions as to what could be causing my vacuum leak?

busa4

is your bov closed while idling? what engine mods have you done? are you using a wideband o2? do you have a tune?

lionelw350

Turbo kit is all thrown on my car but the wastegate flapper is propped open, so i;m not building any boost. Basically its like a big cold air intake.

I'm starting to think that maybe my boost gauge might just be broken (autometer, not the greatest) and that maybe my O2 sensor might be worn out and just not working properly.

And ya i have a wideband (AEM UEGO) that how i know its running lean.

busa4

what about your bov?

lionelw350

Sealed, no air getting passed the BOV. But i did pull out my Wideband sensor and did a little test on it, which it failed. So i'm going to swap it out with a friends sensor just be sure its faulty.

I'm also going to get a speed shop in town to put a master gauge on my car to make sure that my vacuum/boost gauge is working properly as the dealer found no vacuum leaks in my car.

I do have a question though, is it possible that my O2 sensor needs to be replaced and it might not even throw out an engine code? Does anyone have any idea on how to check if an O2 sensor is functioning properly?

lionelw350

So i hooked up another vacuum gauge to my car and it reads 16.5 In.hg. vacuum. So i'm going with the fact that my gauge is broken (damn you autometer!). Is 16.5 normal or should i still be searching for a vacuum leak?

Looked around and couldn't really find anything to give me a definite answer

busa4

16.5 is good. with a warm engine at idle i am at 18-20.