Feels like a misfire under load 🤷****♂️

[blue62]

Originally Posted by ike84

Post 21 - he's pointing at the check valve and says " I'm not sure where this goes". I took that to mean he found it disconnected from the runner, meaning that he has a vac leak. I'm not trying to argue with anyone, just trying to save the guy some potentially unnecessary hassle.

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So from his pictures I made a few assumptions.

1. He is in England and in his video he is driving from the right side of the car so it is a European spec car.
So no SAI system. So no spot to put a vacuum gauge like a U.S. spec. car which has a vacuum port on the front crossover tube left side near the throttle body. In plain view.
2. I assume he took things apart looking for a place to connect the vacuum gauge.
I believe he found the vacuum port for the EVAP system which I think is on the front crossover tube right hand side on the bottom. Out of plain view. So as he moved and turned the rubber collar over the check valve came out.

Not assumptions:

1.He has no EVAP system related codes. Which he should have because if the check valve were out of the vacuum port then the EVAP system could not get vacuum so would fail the first EVAP test by the DME/ECU and would set a code.
So most likely he was not running with the check valve unplugged from the vacuum port.

2.Even if the check valve were missing from the vacuum port the vacuum leak would be from a hole about an 1/8"th -1/4" in diameter. Very doubtful that would cause his issue.

Also if I understand your thoughts correctly your saying there is a possible problem with a vacuum leak where the check valve is supposed to go.
So how would you test your theory????
Put everything back the way it is supposed to go. Then test drive the car???
If that fixed the problem great.
But if the problem is still there he would have to go through the work of getting back into the engine bay, accessing the vacuum port and doing the vacuum test.
That is a lot of extra work to run a simple test. Do it while your there.

[colacharlie]

Originally Posted by blue62

So from his pictures I made a few assumptions.

1. He is in England and in his video he is driving from the right side of the car so it is a European spec car.
So no SAI system. So no spot to put a vacuum gauge like a U.S. spec. car which has a vacuum port on the front crossover tube left side near the throttle body. In plain view.
2. I assume he took things apart looking for a place to connect the vacuum gauge.
I believe he found the vacuum port for the EVAP system which I think is on the front crossover tube right hand side on the bottom. Out of plain view. So as he moved and turned the rubber collar over the check valve came out.

Not assumptions:

1.He has no EVAP system related codes. Which he should have because if the check valve were out of the vacuum port then the EVAP system could not get vacuum so would fail the first EVAP test by the DME/ECU and would set a code.
So most likely he was not running with the check valve unplugged from the vacuum port.

2.Even if the check valve were missing from the vacuum port the vacuum leak would be from a hole about an 1/8"th -1/4" in diameter. Very doubtful that would cause his issue.

Also if I understand your thoughts correctly your saying there is a possible problem with a vacuum leak where the check valve is supposed to go.
So how would you test your theory????
Put everything back the way it is supposed to go. Then test drive the car???
If that fixed the problem great.
But if the problem is still there he would have to go through the work of getting back into the engine bay, accessing the vacuum port and doing the vacuum test.
That is a lot of extra work to run a simple test. Do it while your there.

Okay, so the check valve is not broken it was just some sealant around it not sure why but it’s not broken. I blow through it one way and it’s solid, and the other way air can pass.
So here are the readings from the vacuum gauge in the two different ways that you have suggested…
Oh and does anyone know the thread and size of the fuel rail pressure test port cover as pictured? As they’ve sent me a kit without a size I can use ��

[blue62]

Colacharlie.

Your vacuum readings are low. Ideal would be 17-21 in.hg
I see lots of oil dirt residue on the AOS tubes and other parts of the engine.
So that tells me that you have minor vacuum leaks at the connections and or tubes themselves.
Another common place for a vacuum leak is the oil fill tube that runs from the trunk to the engine. It can rub the edge of the body where it passes into the engine bay. (hope that makes sense).
These are closed system engines with crankcase vacuum rather then pressure.
So anytime you see oil or oil dirt residue on the upper engine area, around the intake, or the AOS you have vacuum leaks.

If your vacuum gauge needle is rock steady when you test then there is most likely no valve train issues. I think your low vacuum is all down to minor vacuum leaks.

With the way your car acts in the video and that fact that it is smooth at any RPM until you give it more gas. Vacuum leaks don't typically act that way once your at around 2000-3000 RPM so I think it may be more of a fuel delivery problem rather then an air metering problem. Low fuel pressure or low volume. Once you step on the throttle there is a momentary lag in the fuel systems ability to meet demand. thats the theory anyway.
Although a faulty MAF (which you have changed out so it is most likely good) or a faulty Throttle position sensor (which has not been tested) could have the same affect.

A confusing thing to me is that you have no misfire codes and your Durametric shows no misfires. Are you certain it is misfiring????

I would do a fuel pressure test at the rail (which I see your preparing to do) next.
There is a spec. for key on engine off. and a spec. for engine running.
If you need those spec. let me know I will look them up.

Sorry I do not know the thread size for the fuel rail test valve.
unbelievable that the sent you a fuel test kit without correct fittings.

[colacharlie]

Originally Posted by blue62

Colacharlie.

Your vacuum readings are low. Ideal would be 17-21 in.hg
I see lots of oil dirt residue on the AOS tubes and other parts of the engine.
So that tells me that you have minor vacuum leaks at the connections and or tubes themselves.
Another common place for a vacuum leak is the oil fill tube that runs from the trunk to the engine. It can rub the edge of the body where it passes into the engine bay. (hope that makes sense).
These are closed system engines with crankcase vacuum rather then pressure.
So anytime you see oil or oil dirt residue on the upper engine area, around the intake, or the AOS you have vacuum leaks.

If your vacuum gauge needle is rock steady when you test then there is most likely no valve train issues. I think your low vacuum is all down to minor vacuum leaks.

With the way your car acts in the video and that fact that it is smooth at any RPM until you give it more gas. Vacuum leaks don't typically act that way once your at around 2000-3000 RPM so I think it may be more of a fuel delivery problem rather then an air metering problem. Low fuel pressure or low volume. Once you step on the throttle there is a momentary lag in the fuel systems ability to meet demand. thats the theory anyway.
Although a faulty MAF (which you have changed out so it is most likely good) or a faulty Throttle position sensor (which has not been tested) could have the same affect.

A confusing thing to me is that you have no misfire codes and your Durametric shows no misfires. Are you certain it is misfiring????

I would do a fuel pressure test at the rail (which I see your preparing to do) next.
There is a spec. for key on engine off. and a spec. for engine running.
If you need those spec. let me know I will look them up.

Sorry I do not know the thread size for the fuel rail test valve.
unbelievable that the sent you a fuel test kit without correct fittings.

Hi blue and thank you for your reply, and also thank you to everyone else who has replied so far.

When I say misfiring- I mean that’s what it feels like, but yes the computer shows no misfires. I had a very similar feeling recently on my motorbike and it turned out to be a coil pack but I thought the best way to describe it at the start of all this was like a misfire. I am also thinking it is probably a fuel issue.

Just to clarify- do you mean that I probably have some small vacuum leaks to address but this will not cause the present problem? Or the small vacuum leaks are the problem? Or are you thinking it is probably the fuel pump, or the regulator, or a injector O ring maybe?

…. And yes please do provide the measurements for the fuel Pressure test if you can buddy Tia ��

Pps- sorry IDK but my pic converter on my iPhone is only letting me compress and not letting me resize unfortunately

[blue62]

Yes it looks from the oil dirt residue that you have some minor vacuum leaks.
I do not think they are the problem. They do need fixed though for optimum performance.
The fact that you can drive the car at any speed or RPM as long as you hold the throttle steady then only get the judder when giving it more gas is not how a typical vacuum leak responds at higher RPM's

So it acts more like fuel delivery issues. either low pressure or low volume.
if it was injectors fouled or not working correctly I would expect the engine to run rough at all RPM
Yours will run smooth as long as you don't demand fuel under load. So if it is a fuel problem I think it would be a pressure or volume issue.

Another possibility is a restricted exhaust.
Both low vacuum and your judder could be caused by a restricted exhaust.

You can test for restricted exhaust with the vacuum gauge.
PITA I know
With engine at operating temp hook up the gauge and hold your RPM as evenly as you can at 2000 RPM for a minute to minute and a half.
watch the needle if it slowly drops from the initial reading you have an exhaust restriction. like plugged cats. or bent exhaust or something not allowing exhaust out.
If exhaust can't get out fuel/air can't get in.

































'

[blue62]

Colacharlie

The only specs. I could find in my book are for 1997-2001 models so you may want to do a search of the forum to see if you can find other specs.
Or post another thread and see if anyone knows.

Here are the specs. I found
engine off key on. 3.8 plus or minus 0.2 bar
engine idling 3.3 plus or minus 0.2 bar

[blue62]

Colacharlie

One more thing sorry.

When you found the P1128 code was your check engine light on?
Erase the code if you have not and lets see if and when it comes back.

[colacharlie]

Originally Posted by blue62

Colacharlie

One more thing sorry.

When you found the P1128 code was your check engine light on?
Erase the code if you have not and lets see if and when it comes back.

I’ll do the checks that you say tomorrow, and thank you for the details on psi’s. Oh, and is this exhaust check you’ve explained to be performed with the vacuum gauge set up as before?

I’m beginning to think that the engine light on the dash is not working, as it did not come on with the fault that is showing on the computer. I’ll also check tomorrow that it’s working when I first turn the key slightly ��

… I was watching this (thanks STL) but I can’t find a fuel pressure regulator as it’s shown in the video

https://m.youtube.com/watch?v=hddx5Ux1v4Y

Unfortunately it doesn’t say the year of his car and I wonder if mine actually does have one or not?

[blue62]

It would be best to just put the vacuum gauge directly into the intake vacuum port and plug the check valve off.
So NO TEE fitting just what ever you need to hook the gauge directly to the intake. If you need a length of hose between the gauge and the intake so you can sit in the car and work the throttle and watch the RPM thats fine.

With that check valve (which connects to the EVAP system) connected and involved in the test there is the possibility that the EVAP system could run it's test while your trying to do the exhaust restriction test.

What happens is that the DME/ECU sends a signal that puts the entire EVAP system under vacuum then checks for leaks over a period of time.
So it draws on vacuum from the intake. If that happens at the same time your holding RPM at 2000 and watching the needle the needle is going to slowly drop just like an exhaust restriction.
So you could get conflicting results.
hope that makes sense.

You may throw EVAP codes or other codes because the EVAP vacuum line it is unplugged during the test.
If you do just clear them after you done testing.

[blue62]

Originally Posted by colacharlie

I’ll do the checks that you say tomorrow, and thank you for the details on psi’s. Oh, and is this exhaust check you’ve explained to be performed with the vacuum gauge set up as before?

I’m beginning to think that the engine light on the dash is not working, as it did not come on with the fault that is showing on the computer. I’ll also check tomorrow that it’s working when I first turn the key slightly ��

… I was watching this (thanks STL) but I can’t find a fuel pressure regulator as it’s shown in the video

https://m.youtube.com/watch?v=hddx5Ux1v4Y

Unfortunately it doesn’t say the year of his car and I wonder if mine actually does have one or not?

The car in the video has it's fuel filter outside the fuel tank on the underside of the car.
I believe your fuel filter is inside the fuel tank. So the fuel systems are a little different. I think the change started with 2002 models.
So you probably have what they call a closed fuel system. My book says the closed system can not be volume tested the way the car in the video is tested.
says you need special equipment.

But you can pressure test at the fuel rail.

[Stl-986]

2002 is when they moved the fuel filter as part of the fuel sender.

Blue - Why do you keep calling the air induction system the evap system? The black/white check valve connects to the air induction which includes the vacuum canister, flapper in the resonance tube and even the valve on tiptronic cars to the tiptronic cooler. EVAP system is for the fuel system like the carbon canister.

[blue62]

Originally Posted by Stl-986

2002 is when they moved the fuel filter as part of the fuel sender.

Blue - Why do you keep calling the air induction system the evap system? The black/white check valve connects to the air induction which includes the vacuum canister, flapper in the resonance tube and even the valve on tiptronic cars to the tiptronic cooler. EVAP system is for the fuel system like the carbon canister.

As I said in an earlier post "It appears to be" connected to the EVAP system.
Perhaps I am incorrect
Which vacuum canister are you referring too???
Where is the EVAP system drawing it's vacuum from on his car??
Vacuum hose layout for European spec. cars would be helpful.

[Stl-986]

the vacuum lines, change over, cannister, check valve, sai are all part of the air induction system, same as ours. EVAP is for the fuel system. Only thing different on his car would be the secondary O2 sensors not being present and a ROW tune, otherwise it is the same as us spec. On RHD the location of a couple parts will just be different, but they will still be there such as the vacuum line to the fuel damper (on the right side of engine instead of left). The intake & vacuum system are all the same as US cars. EVAP is going to be at the front of the car like ours in the right wheel well.

You can get the row PET from here: https://www.porsche.com/central-eastern-europe/en/accessoriesandservice/classic/genuineparts/originalpartscatalogue/

The vacuum cannister is circled in blue:

[blue62]

Originally Posted by Stl-986

the vacuum lines, change over, cannister, check valve, sai are all part of the air induction system, same as ours. EVAP is for the fuel system. Only thing different on his car would be the secondary O2 sensors not being present and a ROW tune, otherwise it is the same as us spec. On RHD the location of a couple parts will just be different, but they will still be there such as the vacuum line to the fuel damper (on the right side of engine instead of left). The intake & vacuum system are all the same as US cars. EVAP is going to be at the front of the car like ours in the right wheel well.

You can get the row PET from here: https://www.porsche.com/central-eastern-europe/en/accessoriesandservice/classic/genuineparts/originalpartscatalogue/

The vacuum cannister is circled in blue:

I did not realize that Euro spec. cars had SAI. thanks for pointing that out.
Even thou the components for the EVAP. system are in the wheel well. The system is still put under vacuum for leak testing by the DME/ECU. So it is connect to a manifold vacuum source somehow.

If you have things like changeover valves, check valves, charcoal cannisters, vacuum cannisters, included as part of various vacuum test you run a high risk of inaccurate and misleading readings.
If a valve energizes and opens to something like a vacuum cannister while your doing a exhaust restriction test. The needle on the gauge is going to drop slowly just like it would if the exhaust is restricted. That is why you isolate as many vacuum operated systems as possible from those types of tests.

That is why I tell the OP to run his test either without the check valve connected or to run two test one with it connected and one without it connected.

What the system is called downstream of the check valve I couldn't care less.
I know it has a vacuum component that can skew the test.
When I tell the OP to include or don't include check valve in the test. he knows what I mean.

[Stl-986]

Just wanted to make sure. You had me very confused when you were calling it the evap system. You have educated me enough so it's all good.

[blue62]

Originally Posted by Stl-986

Just wanted to make sure. You had me very confused when you were calling it the evap system. You have educated me enough so it's all good.

It's all good.
Actually I am not very familiar with Porsche's of any model.
My 2000S is the only one I have ever had "hands on".
But I never have any issues with it so I don't have to dig very deep into it.
But an internal combustion engine is just an air pump. No matter what make of car it is in.
But I do know at least the basics of most systems on older cars like our Boxsters.
Things like EVAP, SAI, they are very similar from one make to the next.
So if you have good knowledge of the basic's of a system it's like a good foundation to a house. You can use and build on that knowledge no matter what make of car they are on.
Things like vacuum testing for diagnostics, using a vacuum gauge to set timing, or carbs on old school cars, compression testing, and general diagnostics I have been doing that for 50+ years.
Now electrics that's my weak spot
I know nothing, not a damn thing about turbo's, except they push air and are more or less free horse power.

[ike84]

The evap system hooks to the plenum just beyond the TB, it runs into the same connector that the AOS breather connects to. It has nothing to do with any of the vac lines that he has pictured so far.

STL is right, some euro cars (Germany and GB) have the SAI system just like ours. There are several different versions of emissions tunes for Europe. Only true ROW cars (sold in middle east for example) did not have the SAI system.

ColaCharlie - do yourself a favor here. There is a diagram of your vac system in the trunk. The line that comes off of one of the bank 1 (passenger side) boots either on the plenum or resonance tube, has become dislodged. As I said earlier, it is the tubing that goes to the SAI and resonance flapper actuator, along with the vac reservoir. Study the diagram, find pics of how everything should be connected (Stl has a nice pic on the post he suggested you read) and hook your stuff up properly. Then see what happens.

This isn't rocket science. You have a vac leak on bank 1. You are leaning out and detonating (not misfiring, big difference) on bank 1. It is happening at WOT because your fuel trims can adjust for the leak while under closed loop operations. When it goes open loop (i.e. WOT) you lean out and throw the code. If you don't believe me, buy a $15 elm327 tester and download your long term fuel trim data. $5 says that your bank 1 is going to be positive and much higher than bank 2 which should be close to zero or at least very low positive single digits.

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[blue62]

Originally Posted by ike84

The evap system hooks to the plenum just beyond the TB, it runs into the same connector that the AOS breather connects to. It has nothing to do with any of the vac lines that he has pictured so far.

STL is right, some euro cars (Germany and GB) have the SAI system just like ours. There are several different versions of emissions tunes for Europe. Only true ROW cars (sold in middle east for example) did not have the SAI system.

ColaCharlie - do yourself a favor here. There is a diagram of your vac system in the trunk. The line that comes off of one of the bank 1 (passenger side) boots either on the plenum or resonance tube, has become dislodged. As I said earlier, it is the tubing that goes to the SAI and resonance flapper actuator, along with the vac reservoir. Study the diagram, find pics of how everything should be connected (Stl has a nice pic on the post he suggested you read) and hook your stuff up properly. Then see what happens.

This isn't rocket science. You have a vac leak on bank 1. You are leaning out and detonating (not misfiring, big difference) on bank 1. It is happening at WOT because your fuel trims can adjust for the leak while under closed loop operations. When it goes open loop (i.e. WOT) you lean out and throw the code. If you don't believe me, buy a $15 elm327 tester and download your long term fuel trim data. $5 says that your bank 1 is going to be positive and much higher than bank 2 which should be close to zero or at least very low positive single digits.

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Ike
I keep looking at the picture in "Car dies" thread that your referring to and also Colacharlies picture.

In both pictures the white end of the check valve is plugged into a three way connector.
In the picture in "Car dies" thread one of the other two legs of the connector , connect to a four way connector. The vacuum canister is just to the right.
The third leg is connected to the electric /over vacuum switch that lets the resonance flapper move.
So if I understand you correctly your saying either the resonance flapper leg is disconnected or the vacuum canister leg is disconnected???
Or am I misunderstanding??

Thanks for the clarification on where the EVAP hooks in. I will check it out on my Boxster tomorrow so I have a visual.

[ike84]

Blue, no worries dude, it has literally taken me 2 years to piece together my understanding of this cars vac system, and there's still more to learn!

In post 21 of this thread he is pointing at the check valve, the black end of which is not connected to anything, and says "not sure where this goes". Check out stls pic - that end should connect to a hose that runs to one of the intake boots. On most it's the bank 1 plenum boot, on mine is the bank 1 resonance tube boot.

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[ike84]

Fwiw, bank 1 vac leaks have been the bane of existence for many forum members over the years. That circuit is complicated, there are a bunch of parts, ALL of them are nearly impossible to access without removing the intakes (at the very least the plenum and resonance tubes), and all can fail. I was recently having a sidebar with Stl about deleting that whole circuit if possible, and when he asked me why I said to prevent vac leaks down the road lol.

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