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

Hello all.

I have a 2.7 2002. The car starts okay and drives okay as long as you stay on a constant throttle. As soon as you try to accelerate a bit harder the car judders and appears to be misfiring. I have change the plugs and a couple of coil packs which looked bad. I have plugged the car into a Durametric (just arrived) and it shows no misfires on any cylinders. I’ve removed the oil filler cap With the car running and the car does idle worse so I’m guessing it’s not the air oil separator.

At any time when driving, if you hold a constant throttle the car runs great, but as soon as you put the car under load you get this big juddering. I will post a picture of the Durametric read out in a while. I only purchased the Durametric tool recently so any advice on how to use it to see what’s going on will be very helpful. By the way the geometric is showing no fault codes at present when driving.

Here’s a list I’ve compiled in case someone sees something I should do first….

Crank position sensor?
O2 sensor?
throttle calibration ?
air leak- vac leak test with smoke?
How test fuel pump is okay?
Idle control valve ?
Dirty throttle bodies?
Fuel pump relay?
Injector sticking open?
Injector seal issue?
Check MAF voltage- new one now installed.
Unplug MAF to see if anything changes?
leak in the intake manifold?

First thing, are there any codes? With the way you are describing it, there should be codes. MIL ever come on, flash?

If you replaced the maf, was it aftermarket or porsche? exact same pn?

cps wont be the issue cause the car starts
o2 sensor - maybe but you need to look at fuel trims & all of the voltages....or just throw parts at it
icv - There isn't one
throttle body - never hurts to clean it properly
fuel pump relay - doubt it,the car starts & runs
injector - possible
intake leak - possible

Proper diag is needed before just doing things.

Video also helps to show what it is you mean. You say constant throttle it is ok, but that is putting load on the car...then you say putting load on the car causes it. Kind of confusing with that. Load is anything above idle.

So how about giving us some background on the car.
How many miles?
Any problems in the recent past??
Any work done on it besides changing plugs and coils in the recent past?
Any Modifications to it?
Are you running a stock air filter??
Automatic or standard transmission?
Has the Check engine light ever come on or flashed?

With performance issues you want to stick to basic diagnostic rules.
The primary rule is:
Simplest things first...... Then work you way up the diagnostic tree step by step from the simplest to the more complex.

With that in mind you could start with re-calibrating your E-gas pedal.
Also a simple "Vacuum test" with a PROPER VACUUM GAUGE.
Not a smoke test.

Those two things are very simple to do.
A proper vacuum gauge is very inexpensive and a valuable diagnostic tool.
The first Vacuum test to do is:
Find a place to connect the gauge directly into the intake.
Have the car fully warmed up:
Let the car just Idle (I believe you Brits call it tick over):D
Record the reading and very importantly the action of the needle if any.
Ideal reading is 18-22 in.hg with a rock steady needle.
Watch the gauge for several minutes at idle look for any changes in reading or needle action.

Let us know how you go.

Look through mine & gabedrummin recent posts if unsure, wealth of info in both of them

Maybe a good fuel system cleaner.?

Sent from my SM-G991U1 using Tapatalk

After market MAF
Nope, no codes, no MIL, doesn’t flash
Throttle body now all cleaned
Yes was thinking of doing a fuel pressure test STL- hoping to get a kit tomorrow

As for the injector- is there a a way to test at home or is it a whip out and take to a specialist thing?

Hi Blue.

How many miles? 147’000 miles with recon engine in 2014 so around 110,000 miles all in on this present engine
Any problems in the recent past?? Nope
Any work done on it besides changing plugs and coils in the recent past? Nope
Any Modifications to it? No mods at all
Are you running a stock air filter?? Yes stock
Automatic or standard transmission? Auto
Has the Check engine light ever come on or flashed? No buddy

Lol at ‘tick over’. Aluminium gets me.

I’ve read your post which relates and thank u for the information.

Yes good idea- I’ll do a video later when I’m with the car 🙏

I’m new to the Durametric myself so is the Egas recalibration done via the Durametric?

Regarding a place on the imlet Manifold to do the pressure test- do you know a good place possibly?

Note- by steady throttle, I mean- take car judders badly under acceleration but take the car upto any speed or rpm’s while driving and then hold the pedal still and the engine sounds perfect (eg at 30mph on a flat road the engine and car sounds as it should). As soon as you depress the gas pedal the juddery missfirery situation comes back again.

To recalibrate the e-gas:

Disconnect your battery for around 15-20 minutes so the computer can drop learned values.
Reconnect battery.
Turn key to on position for 1 minute. Do not start engine... do not touch throttle.
Turn key off for at least 10 seconds.
Start car let it idle for a few minutes to relearn idle fuel map.
take car for a test drive and see if it changed anything.

For vacuum testing go to the thread titled Car Dies go to post #50 on page three
look at the hose marked with the yellow yes you want to tee your vacuum gauge in where it meets the intake just before the resonance flapper.

Let me know how you go;)

Was I correct?? Do you call idle tick over??:D

Damn I almost forgot these cars do not do well with after market MAF sensors.
The only brand you want to use is a Bosch. (Porsche MAF sensors are rebranded Bosch)

Is this the same car that you replaced the VarioCam solenoid in?????

Lol! Tbh I’d say 60 percent say tick over but real petrol heads and older people say Idle 😀

[QUOTE=colacharlie;639911]Lol! Tbh I’d say 60 percent say tick over but real petrol heads and older people say Idle 😀

Sorry about that Blue - I sent my reply at 3am while just up for a bleary eyed wee wee and forgot - yes I did the variocam Unit and solenoid last week as my local garage (who had no Durametric kit) said they interpreted the code as a bad solenoid. Pretty gutted after allot of work to replace it but hey ho, at least it’s ruled that out 👍

Tried that buddy but thank u for your input 👍

[QUOTE=colacharlie;639912] What code? You said it wasn't showing any codes.

At this point it would be a good idea to just do a video of what it is doing. Also with duramtric running graph the following and post a screenshot:

rpm
cam deviation (all values)
cam angle (all values

Do another one with:
rpm
misfires (all cylinders)

Stl unfortunately the garage wrote a code down from their standard diagnostic and then looked it up on their PC to find it was the camshaft actuator at fault, but they deleted the code and we have no record of what it was.

Heres a video of the car after the egas Pedal calibration (batttery off for 30 mins etc process as suggested) ....

https://www.youtube.com/watch?v=I4-RdyNMT94

I’ll do another video today with the durametric data you’ve suggested

‘’A proper vacuum gauge is very inexpensive and a valuable diagnostic tool.
The first Vacuum test to do is:
Find a place to connect the gauge directly into the intake.
Have the car fully warmed up:
Let the car just Idle (I believe you Brits call it tick over):D
Record the reading and very importantly the action of the needle if any.
Ideal reading is 18-22 in.hg with a rock steady needle.
Watch the gauge for several minutes at idle look for any changes in reading or needle action’’



Guys I’ve read your other posts like ‘car dies’ but can’t work out where I’m meant to be connecting for the vacuum test. Might you post a pic of an arrow pointing to the location of it in the engine bay please?

there is a picture in that post

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.

Some things may be slightly different too cause you will have a ROW tune.

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

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

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.

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.

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.

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.

Here is another link:
http://986forum.com/forums/boxster-general-discussions/66666-vacuum-diagram.html

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.

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

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

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.;)

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.

Sent from my SM-G970U1 using Tapatalk

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

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

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

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.

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.

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.

Sent from my SM-G970U1 using Tapatalk