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

[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.