Driving it off the cliff
 

I am about ready to find a cliff and let this car roll off it. Getting tired of fighting it. This is on my 2000 tiptonic

Symptoms - Misfire codes P0300, P0301, P0302, P0303

Replaced so far:
Plugs
coils
spark plug tubes
oil cap
vacuum canister
vacuum check valve
vacuum lines
all O2 sensors
aos
short aos line
long aos line (royal pain to replace)
maf
varicam solenoid
cam plugs
intake plenum rubber connectors

Had 1 shop do a smoke test which they said didn't leak, but dont trust this shop cause I knew the canister was cracked when they did the test.

Removing the oil cap does cause the engine idle to change. HOWEVER, when putting the cap back on, it causes the engine to die as it adjusts idle back. This is the very strange thing. Video here, but the audio isn't all that great. https://youtu.be/drOXhEi4npA

Here is what fuel trims look like.


http://986forum.com/forums/uploads02...1626536216.jpg

One potential vacuum leak source that is often overlooked is the brake booster line. It's seldom a problem on these, but worth looking at. I chased intermittent troubles on a Cayenne for a few months before I figured that one out.

Yup, thought of that one last night. That one appears to be good. Removing it you can hear & feel the vacuum on that line. I have had this in the back of my mind cause my brakes are rock hard, especially compared to my 03. Both have brand new pads & rotors so they should "feel" similar.

Duplicate ignore

Vacuum leaks can cause misfires but your codes are for just bank 1.
So I would look for something that would affect vacuum on just one bank..
General or common vacuum leaks are going to affect both banks.

First thing I would do is a vacuum test with a standard vacuum test gauge at idle.
I would look to see if it pulls vacuum within spec.
But more importantly I would want to know if there is any action from the needle.
You want a steady needle like it is painted on the gauge face.
If the needle ticks that "could" indicate an issue with valve timing.
Which could cause misfires.

That is where I would start as a first step it is a simple and cheap diagnostic test.
It could "possibly" tell you if the issues is related to valve timing or not..
If it tests out good with a rock solid needle then valve timing is good.

Then I would look for other sources of vacuum leaks on that one bank.
So something within the intake system on that head.

Also the electrical wiring to the coils and the injectors.
I think the last two are unlikely mostly because misfires are affecting all three cyl.
Possible but unlikely.



Also did you record the freeze frame data when the codes where set?
It would be interesting to know the conditions when the codes set and if they set under the same or similar conditions every time.

Durametric doesnt do freeze frame unfortunately. Torque does but I haven't see it very useful but will get that info.

Does anyone know what the actual vacuum numbers should be or what the specs are? I have seen different numbers and can't seem to find them in the fsm. Can only see 25 psi at the brake booster in the fsm.

A general spec. is 18-22 in.hg at sea level.

Deduct 1 in.hg for every 1000' above sea level.
So if your in Denver at 5000' and your gauge reads 15 in.hg that would be 20 in.hg at sea level so you would be good.

But remember the most important part of the test is noting the needle action if any.
What I am really looking for is: is your valve timing ok.;)

2 shops checked timing, including the dealer and both say it is in time. Checking myself also confirmed it. That is about the only thing I think that is good.

Keep the ideas coming.

Oh and thank you too

I would still do a standard vacuum test. There may be some value in doing so.

I did one a while ago (about 2 months ago. if I remember right it was around 14 but will do it again tomorrow to see what it's at.

just for kicks what elevation are you at???
14 in.hg sounds a little low!!

St. Louis isn't that high from sea level around 450-500'

That 14 is a big improvement after I did a new canister, vac lines, check valve & plenum rubber.

If I have a leak the only other place I think it could be would be pass side (bank 1) intake gaskets.

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.

That reading indicates a vacuum leak.
Also indicates late ignition timing dependent on action of the needle.

What does it idle like????
Normal smooth??? or lumpy?? or hunting??

When it misfires do you ever feel it???
Do you have an idea of what RPM range it happens???

Also big question I failed to ask sooner any mods?

Easy one...No mods I'm one that keeps things pretty stock with engines.

Never feel the misfires. I can see them in durametric but that's it.

I would call idle lumpy. It isn't hunting like what happens on lawn mower engines.

Here is the weird thing. When the car is cold at startup the SAI turns on as it should. During this time that the SAI is on there are NO misfires. Which indicates an air leak to me but I would expect to see misfires on more then just bank 1.

I need to pick up a better vac gauge. The only thing I have right now is the gauge on a mity vac which I dont think is all that good or accurate.

So RPM kinda rises and falls at idle.
If you sit in neutral and hold the RPM at 1500-2000 does it smooth out???

SAI injects air into the exhaust. Misfires occur in the cylinders.
So no relationship between the two.

Maybe no misfires on cold startup because it is on a richer open loop fuel map.
So possibly the richer fuel mixture is compensating for the unmetered air of a vacuum leak at first startup.

You can get a vacuum gauge at places like O'riellys for around $25.00
Try to get one with as big a face as possible.
Also some still show the green zone, late ign. time area, late valve timing area.
But they are getting hard to find. Not many people use them anymore.
Everyone has got to the newfangled smoke machine. They only tell you one thing.
Vacuum gauge if you know how to read the needle can tell you a hell of alot.

Do I get that right that you`re only getting the misfire codes when the engine is hot? Perhaps the CPS is failing?

I get misfires as soon as the sai turns off. So I would say...warmish & hot.

Tomorrow I will get it out and get Durametric to do some logging. What would be good for everyone to look at? Thinking...rpm, misfire on each cylinder, what else?

Have a vac gauge coming tomorrow. O'rileys was out as was HF.

If vacuum test shows low vacuum with a steady needle then that says vacuum leak.
If lumpy hunting idle changes to smooth running at 1500-2500-2800 RPM
then those two things together are a very very strong indication of a vacuum leak.

since your misfires start as soon as your SAI turns off the vacuum leak is most likely some where in the SAI system.

Would be interesting to compare rough running of cyls. on bank 1 to cyls. on bank 2
I think Durametric shows rough running for each cyl.

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.

Here is a roughness

http://986forum.com/forums/uploads02...1626571098.jpg

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.

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.

Do you mean the sai pump or #15

http://986forum.com/forums/uploads02/sai1626572048.jpg

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

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.

#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.

I caped off the line where it is blue and I put my vac gauge where it is red. No change is reading.
http://986forum.com/forums/uploads02/sai21626575179.jpg

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.

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.

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?

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.

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

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

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.

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

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.

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.

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.

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

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