Driving it off the cliff - Page 2 - 986 Forum - The Community for Porsche Boxster & Cayman Owners

Stl-986 · 07-17-2021, 05:16 PM

As a test I went ahead and used the hand pump and pumped it up to 20hg before heading out to dinner. Came back 2 hours later and it has held at 20hg. This is with it just teed into the vac lines and the engine off.

Stl-986 · 07-17-2021, 05:19 PM

Here is a roughness

I am starting to lean toward intake gaskets on bank 1.

If this gauge is to be believed vacuum is holding steady at 8 with it running. 8 !!

Not sure if I believe it not though, but even if it was slightly off, that is still too low.

blue62 · 07-17-2021, 05:24 PM

Quote:

Originally Posted by Stl-986

As a test I went ahead and used the hand pump and pumped it up to 20hg before heading out to dinner. Came back 2 hours later and it has held at 20hg. This is with it just teed into the vac lines and the engine off.

Have you tried disconnecting the vacuum hose for the SAI from the intake then plug the hole in the intake.
Then see if you still get misfires?

Your test is a good test.
But there is an electrical vacuum switching valve in the SAI system.
Engine off it is not being activated perhaps it is faulty and sticks open with engine running.
Just spit balling.

Disconnecting the vacuum source to the SAI would be a good test.
Simple also.

Stl-986 · 07-17-2021, 05:34 PM

Do you mean the sai pump or #15

Stl-986 · 07-17-2021, 05:36 PM

Or do you mean #18? I know those are known to go bad.

Stl-986 · 07-17-2021, 05:52 PM

Disconnected vacuum line on 18 that goes into the T at the cannister, no difference.

Another test I did was to just disconnect the check valve at the plenum and put my gauge there. Get the same 8hg.

Starting to look like it's an issue with the intake, plenum or flapper in the plennum.

blue62 · 07-17-2021, 06:16 PM

#18 is the switch I was talking about.
I would disconnect at 22 then plug both the intake and the hose to the SAI. Then run the car and see if it changes anything. (misfires) that way you take the vacuum portion of the SAI out of the equation.

If no change then the SAI vacuum system is good and the problem lies some where else.
If it fixes the misfires then the problem is in the SAI system.

Stl-986 · 07-17-2021, 06:27 PM

I caped off the line where it is blue and I put my vac gauge where it is red. No change is reading.

22 is the check valve that goes into the intake. That has been replaced and I tested it and it is working correctly. Old one wasn't and would allow air both ways.

piper6909 · 07-17-2021, 06:56 PM

Quote:

Originally Posted by PaulE

I don't know if it's physically possible, or for that matter advisable on the Boxster. But back in the day we would spray some starter fluid around the intake manifold gasket area on the old British sports cars. If the idle speed increased that was a sign of a vaccum leak at the gasket. But cars were much simpler then, maybe this isn't a good idea on a modern car if you can even get to spray in that area.

Better and much safer than starter fluid is propane. While both can accidently ignite with a spark, with propane you'll just light the torch, which you can quickly pull back and away. With starter fluid, you ignite everything that the liquid was sprayed onto.

Take a propane torch (open but not lit, of course) and run it along everything on the bank1 side of the intake.

piper6909 · 07-17-2021, 07:00 PM

Quote:

Originally Posted by Stl-986

22 is the check valve that goes into the intake. That has been replaced and I tested it and it is working correctly. Old one wasn't and would allow air both ways.

Don't take this as an insult, but since the check valve has been replaced, did you double-check that it was installed in the right direction?

RedTele58 · 07-17-2021, 07:02 PM

Sorry to be late to the party on this one, but I had an almost exact situation last month with my '02S. Same misfire codes on one bank.

I ended up taking mine to my Indy shop where they discovered a bad #4 ignition coil housing on the engine wiring harness. (which looks to me like the only thing you haven't replace)

They state they use to be able to get just the individual housings, but now Porsche wants to sell the entire engine harness. Fortunately for me, they are still able to source the individual units. (And yes, changing one connector housing cleared all the misfire codes)

You may want to check this out before you completely get lost down the rabbit hole.

Stl-986 · 07-17-2021, 07:19 PM

Quote:

Originally Posted by piper6909

Don't take this as an insult, but since the check valve has been replaced, did you double-check that it was installed in the right direction?

No insult taken and it can happen. I made sure it's in the right way with the black towards the plenum

Stl-986 · 07-17-2021, 07:20 PM

Quote:

Originally Posted by RedTele58

You may want to check this out before you completely get lost down the rabbit hole.

I am so far down the rabbit hole I dont know which pill to take...Blue or Red?

Stl-986 · 07-17-2021, 07:28 PM

Going to use my 03 as a test tomorrow.

1st test - disconnect check valve from plenum & connect vacuum gauge. Get reading. If reading is in the 20's I'll do the next step
2nd test - Plug line from flapper to change over valve, take reading. If low, next step.
3rd test - remove rear plenum with flapper and install on 00 car. Disconnect check valve & connect vacuum gauge. If reading is still too low wait for engine to cool down and then replace bank 1 intake gaskets. Take reading again. If low, replace bank 2 intake gaskets and take readings again.

Keep the idea's coming.

ike84 · 07-17-2021, 09:03 PM

I know this isn't gonna help but here goes

Isolated bank 1 misfires confuse me. There aren't any vacuum lines that are isolated to that intake runner. Everything runs to either before the TB or the back side.of bank 2 (where the brake booster line, fuel pressure regulator, and flapper valve attachment are located).

You said you checked the plenum boots - what about the crossover pipe boots? There could be a crack in that.

Did you recently work on the injectors? Maybe one isn't seated properly.

I can't imagine how the runner gasket has gone bad, but I understand your logic though.

Simple thought but have you cleaned your maf recently?

Also, did you get your o2 sensors plugged up properly?

Sent from my SM-G970U1 using Tapatalk

Stl-986 · 07-18-2021, 04:12 AM

crossover pipe boots? All of the plenum boots are brand new
maf is new - also swapped the one in my 03 and no difference
o2 sensors are all new can't really plug them in wrong since the wires are location length specific.

blue62 · 07-18-2021, 05:01 AM

If you do a vacuum test on the intake or at the brake booster with car running at idle and it shows low vacuum.
along with holding RPM at 1500-2500 and the engine smooths out from the lumpy hunting idle then you have a vacuum leak.
Those two things together tell you it is a vacuum leak with 100% certainty.

Stl-986 · 07-18-2021, 05:03 AM

On my 03 at the hole where the check valve goes & cold engine running there is 14hg. The 2000 is doing almost half that at the same hole.

Stl-986 · 07-18-2021, 05:05 AM

This tells me I have a leak somewhere within the intake system. Am I thinking wrong with this?

blue62 · 07-18-2021, 05:07 AM

Quote:

Originally Posted by Stl-986

I caped off the line where it is blue and I put my vac gauge where it is red. No change is reading.

22 is the check valve that goes into the intake. That has been replaced and I tested it and it is working correctly. Old one wasn't and would allow air both ways.

That would test the Vacuum canister and the hoses back to the intake check valve #22
What about the electric switch #18??