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

[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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[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.

Sent from my SM-G970U1 using Tapatalk

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