Over purging??

[V8CER]

Guys
having real problems getting my 99 4.5 running smoothly have changed Plugs, leads.coils and lambda's
at idle (960RPM) with the throttle pots hard against the lowest value (12.2) I am still getting minus 20 as the best adaptive value, all values are similar for both banks ignition timming is a bit low 14 degrees not sure if that is the Austec map? every thing else is OK, I have read the 'Help' notes and assume it is over purging.
If I disconnect the purge line that should prove it but I cant get to it for a few days2. So can someone inform me what the purge valve does, is it cleanable/ replaceable? and any other tips?

Thanks in anticipation

RGDs peter

[Gazzab]

Replace the throttle pots?

[V8CER]

sorry forgot to mention changed throttle pots

[JensenA]

Have you balanced the 2 banks?

[V8CER]

yes balanced,readings the same figures for both banks it is over fuelling which is why the throttle pot reading is at its minimum then on light changing throttle it tends to flat spot because the pot value is so low.

[marcus1970]

They should only be that low when the throttle stop is completely wound down.

The readings should be around 14 to 16 when at idle with around 900rpm.


This is a rough guide - once you have the enginme runing reasonably, you can tweek the pots and idle to get addaptives as close to 0 as poss.

Most peoples aren't 0 at idle, as lots of things affect the fuelling.

MB

[V8CER]

Yes I know that is what I am trying to say if I wind the pots to 16 the adaptives are minus 35ish I cannot get a zero or positive EVER .
I assume I am drawing fuel down the purge line!? or the pump pressure is too high but the adaptive map only shows the issue at low RPM so I believe it to be a Purge valve issue.
Has anyone any experience with the purge valve??

[GreenV8S]

Seems like a bit of a stretch to me, but you could test your theory by disconnecting the purge valve or the purge line. If that cures the problem it would suggest you're on the right lines.

ETA: Just noticed you pointed that out in your very first post, sorry!

So, if it's running rich either the fuel pressure is too high, or the map isn't quite right for that engine, or the engine is using less air than normal at idle, or it's getting some unmetered fuel or other combustible from somewhere. Unless you have the mother of all blow-by problems I think you can probably rule out the last one. Did you check the fuel pressure?

Edited by GreenV8S on Thursday 13th November 23:32

[Old Geezer]

Injectors stuck open, worn or need repalcing?

Why not get it back to Austec and let them tell you whats wrong?

Someone had this problem last week???
Are the lambda sensors plugged in the correct way round?

[V8CER]

checked the lambda's connection OK and response to individual pot movement is correct.All the plugs came out OK so dont think it is an injector.THe map shows lean after 2K which I assume is driven by the pot position?
Austec is an 90 mile round trip and I just cant get it there at the Mo and I really would like to fix it myself I convinced myself that the cost of running the cerb is OK if I do as much as possible myself.
If it is the purge system could I blank the purge line and vent the filler cap ?

RGDs peter

[methodwares]

have you tried setting up the throttles from scratch? backing the idle screw off and disconnecting the linkage rod from one side, then set the t-pots to 15 or so. reconnect the linkage and adjust it if one of the t-pots change as the link bar is too long/short. bring the idle screw back up till the t-pots read 19 (for a 4.2, or 17.5ish for the 4.5).

see what happens, and try resetting the adaptives as well.

[ridds]

I'd send it back to Austec first off. If they've changed the fuel and spark values there's a good chance you won't be able to get a positive adaptive value now. Have you seen a positive adaptive value since the change?