What a vacuum leak can cause.

[S13FX]

SO here is a lil story for you guys.

This weekend I went over to my buddies house to turbo his KA24E. When I got there he said dude I have no idea wtf but my car is ****ed up. So I was like well we gotta get it running in NA before we can turbo.

SO I proceed to diagnose the problem and right away I notcied that one of the cylinders isn't firing when he turned the car over. SO we narrowed it down to his #3 cylinder not firing.

So I proceeded to check for spark, and yes there was spark. Then I was like ok it has to be the fuel, so I changed out the injector with a working unit, check if the plugs works. And proceeded to turn the car on, but the damn thign still wouldn't idle. I was like wtf there is spark and fuel and still no idle. So we check the compression and got 150 all across the board on a cold engine. At that point I was completely stmped.

We have fuel, we had spark, and there is compression and the ***** still wouldn't fire. So for some reason I started looking around his intake mani and started noticing vacuum hoses unhooked I was like wtf. I started hookinh them up. After a while we turn the car over we still got rough idle but the #3 cyl was at listing firing this time. I was like no way. So we procced to take his whole intake side apart removed all the egr stuff and the car is running perfect on 3 vacuum hoses.

But let me tell you I could have never guessed that a vacuum leak could cause one cylinder to not fire at all.

[PapaSmurf2k3]

Maybe it was screwing with the FPR?

[Chezedik]

Vacuum leaks time and again cause awful misfire conditions. Make yourself a boost leak detector. You will find any and all that exist, or will exist under boost. I checked mine to 60psi, with no leaks at all!

[GTR PrYdE]

Vacuum leaks time and again cause awful misfire conditions. Make yourself a boost leak detector. You will find any and all that exist, or will exist under boost. I checked mine to 60psi, with no leaks at all!

a boost leak tester will find vacuum leaks?

[DammitBobby]

Yes.

[jmwenick]

I just hook it up somewhere on the throttle body, open the plate, and pressurize it.

[S13FX]

Well do you have a turbo or no? I would assume yes since your in here .

Cause if you do I would hook it up to the inlet side of the turbo and pressurize it from there. That way you can see if you have any leaks along the IC, see if your BOV leaks, etc etc.

[GTR PrYdE]

Ive boost leak tested the evo, but didnt know it hit vac lines too... kicka**. Thank you!

[S13FX]

Just think of it like this. When the turbo spools up it starts creating positive pressure. There for all the vacuum is replaced with positive pressure. Why else would you connect your boost gauge to a vacuum source, and why else would a boost gauge have vacuum display on it too.

[1995240sxSE]

my boost gauge doesnt have vacume on it

[Florida240sx]

yea it does.. when your car is at idle what is it at? 20 which is what the engine is sucking known as vaccum

[The_Chosen_One]

yea it does.. when your car is at idle what is it at? 20 which is what the engine is sucking known as vaccum

They do sell gauges that are boost and vacuum only.

[Ezzo]

what 3 lines did you leave FPR brake booster and?

[Florida240sx]

That's right they do.... Just never seen one in a car.. But have came across them on the web before.... like that boost gauge 60psi

[1995240sxSE]

When I bought mine I was thinking why do I care about vac. I wish I got one with both on it tho!!! Would make things easier!