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

[colacharlie]

Originally Posted by blue62

Your engine is a little different then mine (I have a 2000S 3.2) so layout may be different.
But if you go to post #50 in the "Car Dies" there is a picture of part of the intake.

Also anyplace after the throttle body that you can attach your vacuum gauge to.
The gauges usually come with a section of hose and "TEE" fitting. So look for a small hose coming off of the intake then use the "TEE" fitting to connect up.
If that is of no help let me know and we will get you sorted.

A few questions:
If you sit in neutral or park can you make the engine judder or misfire by working the throttle or does it on happen while driving.?????

In the video you exhaust sounds a little odd to me even at idle.
Is there any possibility of an exhaust leak????

Could just be the fact that is is a video.
But need to rule things like that out.

Is it a stock exhaust system or aftermarket???

Try this as a test:
Disconnect your MAF sensor (just unplug it) then take the car for test drive. Let me know if it changes anything.

I’m not sure what this was attached to but do you mean put the pressure Tester tube on here?

[colacharlie]

Originally Posted by blue62

Your engine is a little different then mine (I have a 2000S 3.2) so layout may be different.
But if you go to post #50 in the "Car Dies" there is a picture of part of the intake.

Also anyplace after the throttle body that you can attach your vacuum gauge to.
The gauges usually come with a section of hose and "TEE" fitting. So look for a small hose coming off of the intake then use the "TEE" fitting to connect up.
If that is of no help let me know and we will get you sorted.

A few questions:
If you sit in neutral or park can you make the engine judder or misfire by working the throttle or does it on happen while driving.?????

In the video you exhaust sounds a little odd to me even at idle.
Is there any possibility of an exhaust leak????

Could just be the fact that is is a video.
But need to rule things like that out.

Is it a stock exhaust system or aftermarket???

Try this as a test:
Disconnect your MAF sensor (just unplug it) then take the car for test drive. Let me know if it changes anything.

Driven with MAF unattached and no change really.

Here’s a pic of my vacuum test and it shows a very steady 15 hg so …. Now I’ll do the durametric

[Stl-986]

You really should read through my post about driving off a cliff. Will explain a lot as well as show you what goes where, where to put your vacuum gauge, what the devices are, etc.

That black/white device is a 1 way check valve. It does in the hole in your 2nd picture. Plug that back in. Also reconnect the upper AOS hose.

Once that is all re-connected, connect your Vacuum gauge & T to the white side of the check valve and the other into into the factory T.

[Stl-986]

You really should read through my post about driving off a cliff. Will explain a lot as well as show you what goes where, where to put your vacuum gauge, what the devices are, etc.

That black/white device is a 1 way check valve. It does in the hole in your 2nd picture. Plug that back in. Also reconnect the upper AOS hose.

Once that is all re-connected, connect your Vacuum gauge & T to the white side of the check valve and the other into into the factory T.

[blue62]

So first:

It looks to me like the black and white check valve has been broken and an attempt to repair it has been made.

You can check it by removing it then blow into one side then suck on it.
It should pass air in one direction only.

If it has been repaired in should be replaced.

Second:
Your vacuum gauge should have come with a "Tee fitting"
Insert one leg of the "Tee fitting" where your finger is pointing in the second picture.
Then Hook the Vacuum gauge to one leg of the "Tee Fitting" via a section of hose.
With a short section of hose connect the black end of the check valve to the third leg of the "TEE fitting.
Leave the white end of the check valve connected where it is in the picture.
Connected this way your vacuum gauge is in direct line with the intake.

If you connect the gauge the way STL-986 describes then the gauge is connected after the check valve.
You do not want that. That is an improper way to connect the vacuum gauge for and intake vacuum test.

When you do the vacuum test make sure all your hoses in the picture are reconnected.
Have the car fully warmed up.
Connect the gauge then just let the engine idle.
Record the reading and the action of the needle if any.
Then just watch the gauge for a few minutes. See it the needle wanders or ticks or exhibits any action or movement.

Then disconnect the check valve from the TEE fitting and plug that leg of the TEE fitting off.
Now you just have the vacuum gauge connected to the intake.
Run the test again the same way. check for any changes in readings or needle action.

Let me know how you go.

[Stl-986]

Disagree with Blue on the location, but your other pictures show bigger issues.

1st - replace that check valve, it's obviously broken/been messed with. Pricey for what it is. If you are able to blow air through both sides of that check valve, it is bad and can cause problems.
2nd - Dont use that pump/gauge. It will be wrong. Get a real vacuum gauge. You WILL get wrong readings with that gauge. Again, read through my entire post, lots of good info there
3rd - Your rear plenum has the rubber on the wrong side. it should be on the other by the fuel damper
4th - You only want to T into 1 place, you have it Teed into multiple.

I would get all of your vacuum system connected correctly above all. Get everything connected the way it should be (again look in my post there are diagrams/pictures). Once you do all of that then and only then should you T into a line. You want everything still connected the way it should be, all you are doing is taping into a line with the T for a proper gauge.

With the pictures you have posted it really looks like things are just not put together correctly and you have a bad check valve. I bet that once you replace the check valve & get things properly connected & installed you wont have any issues.

[Stl-986]

Here is another link:
Vacuum diagram

[Stl-986]

Here is a video to watch. Might not be your issue, but, does sound like the same kind of issue. idles fine but when you give it gas it has issues.
https://www.youtube.com/watch?v=wEWepuDUes4

He has some good videos to look through as well.

[ike84]

Wait, everyone hold up a minute...

Over the last few days, a clear understanding of the vacuum system components has been bestowed upon me...

That check valve lads to the half of the vac system that controls the SAI function and the resonance flapper.

This means two things -

1 - you have a MASSIVE vac leak if that is not hooked up properly

2 - you resonance flapper is not functional

Both of these things will cause problems while running. Especially the vac leak - stomp on the gas, get a huge amount of unmetered air, run super lean, detonation...which is your problem right?

That is, unless I've totally missed something

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[blue62]

Originally Posted by ike84

Wait, everyone hold up a minute...

Over the last few days, a clear understanding of the vacuum system components has been bestowed upon me...

That check valve lads to the half of the vac system that controls the SAI function and the resonance flapper.

This means two things -

1 - you have a MASSIVE vac leak if that is not hooked up properly

2 - you resonance flapper is not functional

Both of these things will cause problems while running. Especially the vac leak - stomp on the gas, get a huge amount of unmetered air, run super lean, detonation...which is your problem right?

That is, unless I've totally missed something

Sent from my SM-G970U1 using Tapatalk

You are correct with some caveat's.
This is not a North American version. it is a European version boxster
So no SAI system
What he is hooking into is the EVAP system.
At least that is what it appears to be.
The proper way to test engine intake vacuum is to disconnect the EVAP and SAI systems.
Then you test out the EVAP and SAI systems seperately.

So I am trying to have him run two tests one with EVAP system connected via the "TEE Fitting" and a second test with the EVAP system disconnected.
So depending on what the readings are and what the action of the gauge needle is (if any) and any differences from one test to the other(if any).
I will know what to have him test next.
If he has vacuum issues maybe I can point him in the right direction.
We should be able to isolate them to a system. SAI EVAP or Intake

If his vacuum tests are good then there are a few very simple tests he can do with the Duarametric that will tell me if his MAF sensor, potentometer, (gas pedal) and throttle position sensors are working correctly.

If all the above test out good then I would have him move to the fuel system.
Starting with a fuel pressure test at the fuel rail.

Simplest things first:
Go step by step from simplest to most complex
one system at a time.
The simplest system to start with considering his issue is the intake system.

The greatest amount of unmetered air from a vacuum leak is entering the system "at idle".
When you stomp on the gas as you say, the unmetered portion of the air entering the system becomes less and less a part of the whole.
So typically when you have an intake vacuum leak your idle is a little higher because it makes the fuel/air mixture lean and or the idle is lumpy or hunting.
When you give it gas the engine smooths out because the unmeterd air is becoming less and less a part of the entire amout of air entering the system.
If he was running super lean and creating detonation (as you suspect) he should be getting a flashing CEL and some DTC codes. misfire codes something He has none.
So I am trying to go with "my diagnostic procedure" to help him find the problem.
So

[colacharlie]

Originally Posted by blue62

You are correct with some caveat's.
This is not a North American version. it is a European version boxster
So no SAI system
What he is hooking into is the EVAP system.
At least that is what it appears to be.
The proper way to test engine intake vacuum is to disconnect the EVAP and SAI systems.
Then you test out the EVAP and SAI systems seperately.

So I am trying to have him run two tests one with EVAP system connected via the "TEE Fitting" and a second test with the EVAP system disconnected.
So depending on what the readings are and what the action of the gauge needle is (if any) and any differences from one test to the other(if any).
I will know what to have him test next.
If he has vacuum issues maybe I can point him in the right direction.
We should be able to isolate them to a system. SAI EVAP or Intake

If his vacuum tests are good then there are a few very simple tests he can do with the Duarametric that will tell me if his MAF sensor, potentometer, (gas pedal) and throttle position sensors are working correctly.

If all the above test out good then I would have him move to the fuel system.
Starting with a fuel pressure test at the fuel rail.

Simplest things first:
Go step by step from simplest to most complex
one system at a time.
The simplest system to start with considering his issue is the intake system.

The greatest amount of unmetered air from a vacuum leak is entering the system "at idle".
When you stomp on the gas as you say, the unmetered portion of the air entering the system becomes less and less a part of the whole.
So typically when you have an intake vacuum leak your idle is a little higher because it makes the fuel/air mixture lean and or the idle is lumpy or hunting.
When you give it gas the engine smooths out because the unmeterd air is becoming less and less a part of the entire amout of air entering the system.
If he was running super lean and creating detonation (as you suspect) he should be getting a flashing CEL and some DTC codes. misfire codes something He has none.
So I am trying to go with "my diagnostic procedure" to help him find the problem.
So

Hi again one and all.

I’ll redo the test In the way You’ve suggested but here’s what I found yesterday …

https://youtu.be/LBDL8U04HRE

https://youtu.be/ra3oX95adVM

[blue62]

The first thing you need is a proper vacuum gauge.
A mighty vac like your using is not ideal for for the type of tests we are trying to do.
Google automotive vacuum test gauges or look up some you tube videos on automotive vacuum testing. Then you will see the type of gauge I am talking about.

Then do the vacuum test with it hooked up the way you had it in your pictures.
Then run the test again but disconnect the check valve from the TEE fitting and run the test again.

I need readings and needle action from both tests..

The P1128 code is for a lean condition on bank 1
So did the Check engine light come on???

Lean conditions can be caused from many things.
Bad sensor like the MAF
Bad O2 sensors
Exhaust leaks
Vacuum leaks
valve train issues.
Fuel delivery issues.

The reason I had you recalibrate the E-gas
The reason I am having you do the vacuum tests
also the reason I had you unplug the MAF
all the things I am having you do is how I would go about trying to finding the cause of the problem.

Simplest to most complex step by step one system at a time.

[ike84]

Blue, I'm not disagreeing with your testing. It doesn't make sense to me though to ignore what the OP has showed us and recommend extensive diagnostics instead of telling him to fix what is broken and see if that resolves the issue.

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[Stl-986]

In blue's defense, From the beginning there were no codes....now there are.

[Stl-986]

OP - You should re-size your pictures also, they are just too big.

[blue62]

Originally Posted by ike84

Blue, I'm not disagreeing with your testing. It doesn't make sense to me though to ignore what the OP has showed us and recommend extensive diagnostics instead of telling him to fix what is broken and see if that resolves the issue.

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Tell me what it is that you see broken???

[blue62]

ColaCharlie,

One thing I forgot to mention is that you want your climate control (heater air conditioning) turned off when you do the vacuum tests.

[Stl-986]

That white/black check valve looks broken

[blue62]

Originally Posted by Stl-986

That white/black check valve looks broken

Yes
Go back and read post #25
I told him a simple effective way to test it.
I also suggested he replace it if it had in fact been repaired.

[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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