CTR_B

iTrader: (1)

I can't seem to figure out why my car has a continuously lean A/F (15.0 to 18+) condition. Doesn't matter if I'm in boost (wot) or just driving normal (partial Throttle).

When my car was tuned it was on pump 93 oct and while under boost had a 10.5 - 11.5 A/F but today on the way to the king meet I notice a power loss and the 15-18+ A/F ratio.

I have a walbro 255, 450cc DSM injectors, B&M Adjust FPR and the FP gauge say 50psi with the hose disconnected and between 45-48psi (hard to tell) with vacuum.


Any thoughts/ideas would greatly help.

CTR_B

iTrader: (1)

What would cause the engine to lean out like this?

tagperformance

Bad fuel pump or clogged fuel filter

CTR_B

iTrader: (1)

Fuel pump is bran new... Walbro 255. How ever I am not sure about the fuel filter, But I still have 50psi at the gauge. (gauge is on top of the filter)

Joseph Davis

Ignition misfires will cause lean conditions. If it's not fuel pump (doubtful, Walbros are pretty stout whether china knockoff or not) or fuel filter (likely) like the gentleman before me suggests, then what probably happened is you glazed your plugs by running too rich for a period of time. 11.5:1 is the max cooling you get from AFRs for most (not all) water jacketed engines, and a lot of cars are lightly misfiring at 10.5:1... which makes that 10.5:1 reading a somewhat lean reading caused by misfires.

CTR_B

iTrader: (1)

Is it possible to take the plugs out and clean them lol? or am I in need a some new ones?


Like I said Im not sure on the life of the filter but I'll look into replacing that tomorrow just to see and if I can't clean the plug I suppose I have to by new ones as well.

I just do understand, When I start my car and it's at idle my Wideband will show 14.xx for a second then it stays pretty steady at 15.6 till on get on the gas then it just goes up.

would previously running 110oct have any affect/cause this issue?

Joseph Davis

If you have a Bosch sensor attached to your wideband it can be harmed over time by leaded fuel like 110. You might want to verify with another sensor before going any further using your wideband as a diagnostic tool.

CTR_B

iTrader: (1)

I ran 4 gallons of 110 once, Would that actually be enough to harm it?

grndcont

dude, i have the same problum. i have the dsm 450's, a brand new walbro lp pump, and a brand new filter. it runs fine on the dyno, but every now and then when i'm driving (especialy when stoped) it just pegs lean. the car noticably bogs down, and runs like ****. i'm deployed right now, but when i get back i was going to change out the dsm's and see if that helps.

thinking back, i might replace the pump as well, the dsms worked fine before i changed that out.

CTR_B

iTrader: (1)

Everything was good up until today. I just went out and started the car, When I hold the throttle to about 2500 rpms I notice a fast vibration as if maybe a missfire? It's too late to truely test and find out but I will be sure to in the morning.

I hope joseph was right and its only my plugs being fouled..

grndcont

i think a missfire or fouled plugs would cause more of a rich condidton. the mixture would not be fully burned in the cylinder, and would show up on your wideband as excess fuel in the exhaust.

Joseph Davis

Since a wideband OXYGEN sensor detects oxygen in the exhaust, not fuel, you are wrong.

CTR_B

iTrader: (1)

Hmmm

Flashmn

My car bogged down and seemed lean when boost hit, turned out to be a f'd up coil.

CTR_B

iTrader: (1)

I can tell this isnt going to be easy

grndcont

dude, a wideband oxygen sensor detects the proportion of oxygen in the remaining exhaust gas. think of exhaust as a compound gas, containing nitrogen, water vapor, carbon dioxide, carbon monoxide, hydrocarbons, nitrogen oxides.
dont be fooled by it's name. it's looking at all of this and what the ratio is, I.E. "air-to-fuel ratio"

jjspec

If you are misfiring there is more o2 in the exhaust because it didnt get burned in the combustion process, just passed through the cyl with the unburned fuel. Good luck.

grndcont

CTR B I apologize for helping to take this post away from its intent. please keep us updated on your progress.

CTR_B

iTrader: (1)

Please explain what you mean by this?

Would a turbo with a blown intake seal cause this?

The fuel filter is less then 2yrs old, The fuel pump is less then 4mo old, The tank was dropped and cleaned 2yrs ago, I have 50 psi with out vac and 45 psi with vac so that means my FPR is good right?

I tried even turning the PSI up on the FPR to 80 psi and it still never went bellow 15.60 A/R. The only time you can see it bellow 15.6 is when the car is Ice cold, Then you'll see it go between 14.5&14.8 for a few seconds then it'll go back to 15.6

I notice a significant power loss under wot and a good studder (Bogs the takes off) when trying to accelerate under partial throttle in 3rd or 4th gear.

Joseph Davis

I'm fairly well versed in what a wideband does, thank you. What does any of this jibber jabber have to do with a misfire creating a false lean reading, and not a false rich one as you have stated?