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jtravers · Mar 16th, 2010, 12:32

Thanks 960kg - and agreed, probably too much detail, but I will counter the fuel pump theory with some more ;-) The pump I put in is exactly the one you recommended in your post - I think the 255 designation is a family while the GSS342 is the subtype or some such:

http://cgi.ebay.ie/ws/eBayISAPI.dll?...=STRK:MEWNX:IT

And you can be as rude as you like, given that you saved me €€€ on the Volvo fuel pump with the information you provided.

Anyway, I also did all of the fuel pressure tests in Vadis and no issues, along with trying the fuel pressure tester in the driver's cabin (!) to see the readings under full flow - also fine.

When I said open loop I wasn't being clear enough, I meant only open loop prior to running conditions - I have checked this on my OBD scanner and it does take a couple of minutes for the system to go CL. Then it drives ok under almost all conditions, idle, WOT, etc.

I'm glad you agree with my suspicion, Old Painless, that being able to blow clear from the air cleaner intake through to the oil filler cap with little resistance is odd to say the least. And, as a compression test showed no variation between the cylinders, I don't think it's a major mechanical fault. That is what got me to the crankcase ventilation system. Could there be any other route this air is taking?

I haven't really looked into the rear lambda sensor as a cause as I thought this was mainly to test the condition of the cat - will check that out.

The exact symptoms I am seeing are: when I start in the morning it will generally idle fine (I cleaned the IAC valve a while ago and works very well now). If I touch the throttle at all the engine will stutter, drop revs to almost cut out and then recover with the IAC again. This reduces as it heats up, and is gone when the OBD shows CL. The remainder of the drive is fine regardless of conditions, but the fuel trims are off the charts.

I performed the compression test with the throttle closed, which I gather now is the wrong way to do it. Anyway, the values I got were 12.5 bar on 3 cylinders and 13 bar on the other.

A few more posts like this and we can publish this as a novel.

Mar 16th, 2010, 12:32	#9
jtravers Junior Member Last Online: Oct 6th, 2010 17:18 Join Date: Mar 2007 Location: Rush, Co. Dublin	Thanks 960kg - and agreed, probably too much detail, but I will counter the fuel pump theory with some more ;-) The pump I put in is exactly the one you recommended in your post - I think the 255 designation is a family while the GSS342 is the subtype or some such: http://cgi.ebay.ie/ws/eBayISAPI.dll?...=STRK:MEWNX:IT And you can be as rude as you like, given that you saved me €€€ on the Volvo fuel pump with the information you provided. Anyway, I also did all of the fuel pressure tests in Vadis and no issues, along with trying the fuel pressure tester in the driver's cabin (!) to see the readings under full flow - also fine. When I said open loop I wasn't being clear enough, I meant only open loop prior to running conditions - I have checked this on my OBD scanner and it does take a couple of minutes for the system to go CL. Then it drives ok under almost all conditions, idle, WOT, etc. I'm glad you agree with my suspicion, Old Painless, that being able to blow clear from the air cleaner intake through to the oil filler cap with little resistance is odd to say the least. And, as a compression test showed no variation between the cylinders, I don't think it's a major mechanical fault. That is what got me to the crankcase ventilation system. Could there be any other route this air is taking? I haven't really looked into the rear lambda sensor as a cause as I thought this was mainly to test the condition of the cat - will check that out. The exact symptoms I am seeing are: when I start in the morning it will generally idle fine (I cleaned the IAC valve a while ago and works very well now). If I touch the throttle at all the engine will stutter, drop revs to almost cut out and then recover with the IAC again. This reduces as it heats up, and is gone when the OBD shows CL. The remainder of the drive is fine regardless of conditions, but the fuel trims are off the charts. I performed the compression test with the throttle closed, which I gather now is the wrong way to do it. Anyway, the values I got were 12.5 bar on 3 cylinders and 13 bar on the other. A few more posts like this and we can publish this as a novel.