Normal fuel pressure?

[Andy]

Good evening all.

I’ve been battling this problem for a long time, now I’d finally like to get it sorted once and for all.
Basically the car idles low (around 500-600 rpm) and lacks power/misfires while on the move. When I say it lacks power and misfires, the misfire is just noticeable (especially on an average speed duel carriageway for example) and I can feel it doesn’t quite have the pull it used to if I put my foot down.

In August last year I started checking various potential causes, and I thought a good place to start would be to check the compression. I tested it 3 times just to be sure.

The results:

1st test: - 1: 230. 2: 224. 3: 225. 4: 233

2nd test: - 1: 236. 2: 235. 3: 229. 4: 232.

3rd test: - 1: 238. 2: 236. 3: 235. 4: 241.

With the test, I held the throttle all the way open at the throttle body and had someone crank it until the needle stopped moving on the gauge (I’m not a pro mechanic, so wether this is the correct procedure... ).

Next I tested the fuel pressure.



That’s 2.4 bar (I think) plus or minus at idle (500-600 rpm).
A video for better reference:



As you can see, it goes up with the revs and then settles back down at idle. Should it do this?

Could a weak/dying or incorrect fuel pump cause these symptoms?
I’ve changed the crank sensor, the coil and the plugs. The ht leads and fuel filter are both relatively new, and I’m not getting any EMLs for any other sensors... I don’t know what else to possibly check.

Any help or suggestions would be very much welcomed.

Thanks.

 

[TomF]

Compression figures look good mate, they are all within spec

Fuel pressure should be 3.0 bar with the vacuum pipe to the regulator removed, yours looks to be behaving normally.

 

[Andy]

Ok, well that’s good to know. Maybe two things I can check off the list. Thanks Tom.

Could there anything else which may cause poor idle without throwing up an EML.

 

[TomF]

You could try another fuel pump to see if its any better, a weak pump will still make pressure but will struggle under load.

Have you tried cleaning the idle control valve to see if that brings the idle speed up?

 

[DavebGsi]

You could try another fuel pump to see if its any better, a weak pump will still make pressure but will struggle under load.

Have you tried cleaning the idle control valve to see if that brings the idle speed up?

Yea, ideally you would drive it down the road with gauge still on it to see if the fuel pump can keep up. have you done anything like clean the airflow meter?

 

[DavebGsi]

well done on renewing ur membership btw

 

[Andy]

Thanks for the suggestions fellas, I’ll certainly give them a try.

I got a new fuel pump from AutoVaux the other day, but I’m in a shitty situation right now and I’m afraid to change anything (if it’s running and starting, I’d rather leave it for now unless it might possibly help pass the MOT).

 

[Andy]

well done on renewing ur membership btw

It was the only way I could add the video above, or so I thought. Computers were never my strong point.

 

[DavebGsi]

It was the only way I could add the video above, or so I thought. Computers were never my strong point.

Good you should be supporting the club haha then u can ask for help

first thing, u need to ceck the pressure while driving