timing - lean engine question

[Vt-Brrrlina]

just a question for those more in the know...

as of recent had heaps of proplems with my vp v8
backfiring etc..

its now fixed thanx to you guys cheers

have replaced

O2 sensor
dizzy cap
rotor
leads
spark plugs
had injectors cleaned
new belts
new oil
new fuel filter and oil filter


anyway my engine light is still coming up lean error code on occasion have now done a 1000 k;s since the last backfire and no hint of problems in that sense jsut wondering what your thoughts are

i have retimed the engine to as close as possible to 10 degrees which is what its supposed to be -

i guess my question is does timing have anything to do with my engine running lean and for what reasons wouyld you increase or decrease your timing???? otherwise any more ideas why it could be running lean

cheers
Ben

[Morton]

Did you set the timing with the diagnostic terminal shorted? I'm sure you did, but just checking

You generally retard timing if the engine is pinging - and that generally happens when it's running too lean - which leads to hot-spots and predetonation.

I think. Don't quote me on that.

[Vt-Brrrlina]

yeh was in diagnostic when i set it - and worked a treat - sounds heaps healthy cept for the engine light - just figure there must be a way to kill it lol - without taking the bulb out lol

just not sure what timing actually does and whether its an issue - ive got no idea what mods to my engine if any - its standard ex police - pacemaker extracters and cold air intake if that also helps
i also put 18 inch chromies on and noticed it treks along at lower rpm on average so dunno if this affects anything at all????

[Vt-Brrrlina]

**bump*** anyone please ?!?!?!?!

[Not_An_Abba_Fan]

Running lean is most commonly a vacuum leak.

[immortality]

since checking the error codes, have you reset the ecu to clear the codes it has stored?

when you had the injectors cleaned, did you get a report that gave you before/after flow figures etc.

does the idle roll/stumble a little (indication of vac leak), it's also possible you have a fuel pressure problem but check the vacuum first as it's easier and cheaper. to check fuel pressure you will need a pressure gauge

[Vt-Brrrlina]

have checked fuel pressure all good - so will check vacuum leak next cheers for ya input

[VrWagz1]

^^^^^as above have you cleared the codes yet. The dont clear themselves, you need to do it or they just keep showing up.

[Vt-Brrrlina]

yeh sorry have cleared the codes and doen the rev up to 3000 rpm for a coupla mins to reset the idle air controller

[immortality]

possible dodgy O2 sensor. did you get a genuine holden one or a cheap ebay jobby? something else to check is you exhaust manifold gaskets. a leaking exhaust can in some circumstances let air in possibly causing false O2 readings.

[Vt-Brrrlina]

ah ok nah went to repco and suipposedly got the proper o2 sensor , and have been to the exhaust fella just recent to get the extractors welded up he assures me no leaks - hmm has me stumped

on a side note what does timing do -- eg advance or retard why would u adjust it it it needs adjusting

[Morton]

Timing is all to do with when the spark happens in relation to engine rotation. i.e. whether spark occurs at Top Dead Center, or slightly before (advance) or slightly after (retard).

And then of course the 'degrees' of advance or retard relate directly to the number of degrees of crankshaft rotation.

[Vt-Brrrlina]

ok - so having pacemaker extractors, otrcold air intake and running premium inleaded - is that gunna require any timing advances or retarding or is that nothing to do with anything/

[Morton]

Not at all You should always have the timing set at 10deg advance in diagnostic mode, depending on your tune.

For a car without a tune, you can advance to around 14deg and get good power, but it's better to set it to 10deg and have the spark changed in the memcal

Spark always changed through the rev range. The 10deg advance is only base timing. For example, timing will be set at 20deg? I think when idling, which is why you short the diagnostic plug under the dash, so the timing reverts to base.

[Vt-Brrrlina]

ah ok - yeh did it to 10 deg in diag mode i think lol - i read that each mark is 2 degrees and i went from the advance side

||||A||||R||

think it goes something like that so timed it from the left

[Morton]

Sounds about right Five notches to the left is where it should be at. You can eyeball it at the dizzy if you like - but I did that, and it came out at 15

[Vt-Brrrlina]

ha ha nah went an bought a timing gun and did it as good as i could seems to run alright just with everything ive done cant stop the computer coming up running lean so its got me stumped - off to the mechanics i thinking