Vacuum leak located... sort of

[Tishabet]

You guys may recall that I was having a rough idle problem a while back (see this thread) and after trying out the "spray starter fluid around your engine" technique, I found a spot that rings the cherries:



When I spray the fluid anywhere around the vicinity of the FPR the engine goes a little haywire, particularly when I spray under the fuel rail. So now I know the vicinity of the leak, and can even hear it if I get my head close. However, I can't seem to find the leak itself... I did a parking lot examination of all of the vacuum tubes I could find in the area, but didn't see or feel anything amiss. Is there a "gotcha" spot for a leak in this area? I feel a bit ridiculous asking this question... I mean, there is a vacuum leak somewhere in this 6 inch by 6 inch area, but I just can't seem to find it. Any thoughts?

Thanks in advance!

[exitwound]

What if the intake seal on the last cylinder is broken? Easy 20-30 minute fix if it is. There's really not much else there other than the FPR and the vacuum lines and that junction in the vacuum line.

[Tishabet]

Originally Posted by exitwound

What if the intake seal on the last cylinder is broken? Easy 20-30 minute fix if it is. There's really not much else there other than the FPR and the vacuum lines and that junction in the vacuum line.

You mean the seal between the intake manifold and the block? Hadn't considered that it might not be a vacuum line causing the vacuum leak... I'll take a peek.

[exitwound]

It's just a guess, and it would obviously lead to air getting into the combustion that wasn't measured by the AFM.

[Tishabet]

Hey, guesses are what I'm after at this point!

[968rz]

I've seen leaks at the intake gasket before. Get a 3' piece of vacuum hose and hold it in your ear (carefully) as you move the other end around the suspect area (maybe add a straight bit of brake line on the end to make it easy to point) you'll soon know right where the leak is.

[Jeff Laurence]

Maybe an O ring on the last injector?

[Tishabet]

Man, you guys were spot on! Look what I found when I stopped looking at the vacuum lines and started looking at the intake manifold:



New seals are on the way. Do I have to remove the fuel rail/injectors and do the full dissasembly to replace the seal, or can I get away with just loosening up the entire manifold enough to slip the new seal into place? Either way, I owe you guys... thanks!!

[exitwound]

You should be able to loosen the manifold from the block enough to slide them in and out. However, avoid bending them as much as possible of course. There will be spark plugs and the fuel rail in the way when you try to slip them in. Removing the fuel rail isn't that big of a deal. It's 4 10mm bolts and the o-rings of the injectors themselves that need to pop out. With the fuel rail lifted, you can get a good 1/2-1" of clearance when you pull the manifold up.

Woohoo on an easy fix though! Glad we could help!

[Techno Duck]

Fuel rail can be left connected to the intake manifold, just sort of lay everything to the side. There is a good possibility you will need to scrape the old gasket off, in my experience when they are that old they do not come off in one piece.

[choinga]

yes - and make sure you cover the holes FIRST before you start scraping or attempting to remove the gasket - don't need any nasty gasket parts down inside your engine!!

[Tishabet]

Thanks for the advice guys! I mostly want to avoid removing the rail so as not to disturb the seals on my injectors, which I hear are a pain to purchase and replace. Will definitely avoid losing any pieces of gasket in the engine!!!

[evan200]

Originally Posted by Tishabet

Thanks for the advice guys! I mostly want to avoid removing the rail so as not to disturb the seals on my injectors, which I hear are a pain to purchase and replace. Will definitely avoid losing any pieces of gasket in the engine!!!

if you are worried that unseating the fuel rail will disturb the injector seals, then it might be a good idea to replace them anyway, Pelican has the o-ring kits for under $8, and the seals are about $0.25 each. I got mine from the local Advanced and did really have that much trouble replacing them. YMMV though. Good luck.

[krystar]

and after yer done scraping, take a shop vac and vacuum the area for good measure anyway.

[HondaDustR]

I had the exact same thing happen. Check this out if you like pictures.
Fuel injector job in pictures.

Get yourself some AOS seals while you're at it, since if they aren't leaking yet, they will be...and the only way to fix them is with the intake off.

[TexasBlake]

Originally Posted by Tishabet

Man, you guys were spot on! Look what I found when I stopped looking at the vacuum lines and started looking at the intake manifold:



New seals are on the way. Do I have to remove the fuel rail/injectors and do the full dissasembly to replace the seal, or can I get away with just loosening up the entire manifold enough to slip the new seal into place? Either way, I owe you guys... thanks!!

Removing the fuel rail is simple:

http://www.texasblake.com/porsche/tech/fuelrail.html


Taking the manifold off completly isn't too bad, but you may be able to leave it part of the way connected to all the BS stuff towards the back. here's how to remove the intake:

http://www.texasblake.com/porsche/tech/intake.html

[Tishabet]

Should have updated this thread: bought replacement seals etc for injectors and replaced the gaskets about a month ago, have been purring along ever since!