Been doing a bit more tuning and now got it quite responsive.. but.....

have a bit of popping at idle which i have eased quite a bit by setting the zero thottle afr targets slightly richer and tung to them..

problem is i am now getting a bit of backfiring when i let off the throttle

any ideas where i am going wrong?

cheers

I assume you mean spitting back through the throttle bodies?

Its one of two things, either ignition too far retarded, or too lean.

If its just when you lift off the throttle the popping should be in the exhaust. Have you set your overrun fuel cut too lean? Or have your bottom row of the VE tabel too weak?

The theory is if its too lean there isnt enough fuel to burn in the combustion chamber so it gets dumped in the exhaust, eventually it builds up enough fuel in the exhuast for it to ignite and go bang.

Can you post your MSQ?

David

yes sorry should have been more clear..

popping was back through carbs and i have made that richer by tweaking the afr targets so successive runs with megalog viewer dont try to lean it off again. that has all but cured the popping i have a small amount of hunting at idle so i guess i have a small leak on the inlet manifold somewhere need to get a new gasket for that.

as for the back firing.. well that is from exhaust but having spent a coupe of hours researching on here and the internet... i went back out to check my exhaust over and sure enough i have a leak from one of the primaries where it goes into the 4-1 collector just been trying to seal it but i think i am going to have to strip it down to the job properly

one thing i have noticed in my logs is that the afr reading is fluctuating quite wildly.. could that be because the leak is upstream of the sensor?

are you going to the bbq on sunday david? if so, see you there

[Edited on 24-6-09 by DaveFJ]

Yes, any air leak in your exhaust will adversely affect your lamda readings and its pretty important you get it fixed so you can get a stable map.

Hunting at idle is a sure sign of an air leak on the inlet somewhere, and may also be the reason you can't get a nice lean idle.

That said I cant get my pinto to idle nicely at anything over 13.5AFR

PS yeah i should be at the BBQ as long as the weather is nice

[Edited on 25/6/09 by flak monkey]

well sealing the leak on the exhaust seems to have been successful - for now.... still to find out if the exhaust backfire is cured...

got a new intake gasket today so will fit that tonight and try to cure the idle hunting and see how i go from there

Gasket was wildly expensive at £3.60 from Bennets!