Air fuel ratio query (LC-1 fitted today) advanced question!?

5th February 2011, 22:03

I know I have a problem with my idle as its runs super rich whilst the choke is on from cold but it runs rich on idle when warm anyway.

I just fitted my LC-1 today, seems to be working properly and my gauge adjust itself but the readings on idle are 10.3 : 1 on average :/

I think im right in saying that gasoline engines should be 14.6 to 14.9?

also does idle generally show a richer reading? I can get 14 ish when im driving along and gauge shows 22 when backed fully off of the throttle.

Anyone got this setup? or know much about air fuel?

5th February 2011, 23:17

i know youre right in that the stoichiometric ratio, at which combustion in a petrol engine is most efficient, is 14.7:1. so you are running rather rich there :/

and im not sure but im thinking on idle itll run slightly richer becuase you dont have the 'ram air' sort of effect youd get when driving, as no air is being forced through the induction system like it would through your gill when youre moving forward. if that makes sense. also when youre backed off the throttle the system will ony inject enough fuel to keep the engine going whilst you deccelerate, hence the lean mixture there. not sure on this tho XD

have you checked things like temp sensors, map and maf sensors? cos if those sensors have an internal resistance or an internal fault the ecu could be tricked into thinking the engine is cold, or that there is more air coming in than there actually is, and so will dump more fuel into the engine

5th February 2011, 23:22

sorry had another thought XD you checked your air filter? if thats dirty you wont get enough air through and thatd cause it running rich. also check things like thermostats, like if the engine is warming up atall. or see if youre injectors are leaking. maybe lambda sensors? if theres a carbon build up on the one nearest the mani (before the cat) then the ecu will think the engine is running lean and will inject more fuel in. could be quite alot of stuff XD

6th February 2011, 00:25

Cheers for the post, much appreciated. I did try and do some research before posting so that I sort of knew what I was talking about :/ ? lol

Good call on the rich running on idle might be right there!
Ive tried fitting a friends sensors to my car but it didnt stop it missing and running super rich on idle (sounds cammed when first started)

After all the things ive tried Ive not cleaned my air filter and I know its quite dirty, hopefully try that tomorrow

Oh and Ive just fitted an innovate LC-1 with gauge so its not the first lambda im sure, also the second one is new and in an alloy sleeve in the engine bay.

Can anyone confirm if lambda's run richer by loads on idle?

Cheers all

6th February 2011, 09:32

its quite alright

hopefully i was some help. kinda a bitch to diagnose cos any sensor in the fuel system can screw the ecu about lol. good luck with the air filter! fingers crossed lol

8th February 2011, 10:24

not had time to do the air filter yet but anyone got an idea about air fuel ratio's?