Cold air, leaner A/F ratio...normal or problem?

[tekdeus]

It was cold out tonight, but no where near freezing. I noticed my AFR's which were tuned to 11.5 hitting 12 and 12.5 on occasion. Would cooler air do this? I don't see how unmetered air could be leaking in... Do I need to retune for winter? Running Lex AFM, SAFC, 550's, etc.

Also, my Lex AFM and accordian pipe had a very light coating of oil, and I think it's from my PCV setup. Should the AFM be cleaned, and what would be a safe product? Brake cleaner? Just wondering if the oil might be affecting the readings.

 

[jdub]

Don't clean the AFM electronics, it's a sure fire way to trash the module...especially using carb or brake cleaner. The "MAF" cleaner you find at parts stores are just as bad. The 7M Karman Vortex sensor uses a foil mirror...any of these products destroy it. You can remove the electronics and clean the AFM body if you wish. If you're using a K&N filter, that is the source of the oil. I'd get an AEM Dryflow filter...the K&N filters are crap.

Cold air = denser air. This can cause a lean shift and you will hit fuel cut earlier too. It depends on how you have the SAFC tuned to modify the Ks output from the AFM.

 

[gaboonviper85]

It was cold out tonight, but no where near freezing. I noticed my AFR's which were tuned to 11.5 hitting 12 and 12.5 on occasion. Would cooler air do this? I don't see how unmetered air could be leaking in... Do I need to retune for winter? Running Lex AFM, SAFC, 550's, etc.

Also, my Lex AFM and accordian pipe had a very light coating of oil, and I think it's from my PCV setup. Should the AFM be cleaned, and what would be a safe product? Brake cleaner? Just wondering if the oil might be affecting the readings.

do not spray anything on your afm....it is very very sensitive and will be ruined....the oil from you pcv shouldn't have back traveled as it's behind the afm....are you running an oiled airfilter such as a k&n?

Cold air shouldn't make you run lean unless something is wrong with the afm signal as cold air requires extra fuel...don't really know what to tell you other than don't touch the afm.

 

[gaboonviper85]

jdub beat me :-(

 

[tekdeus]

I'm using a dry Apex'i filter, I forgot to mention that. Perhaps it's my recirculated BOV that is pushing some of the oil and vapors back towards the AFM? It lets out a hell of a lot of air at 15psi.

 

[gaboonviper85]

I'm using a dry Apex'i filter, I forgot to mention that. Perhaps it's my recirculated BOV that is pushing some of the oil and vapors back towards the AFM? It lets out a hell of a lot of air at 15psi.

Could be but I think the vacume caused my the turbo and motor would still suck more than the bov...it should keep all vapors clear of the afm...but I'm no scientist..

 

[grimreaper]

ive seen the pcv blow by build up and make its way down to the filter, (no catch can, pcv port is at an angle on the side of the pre turbo intake tube, filter is lowest point on intake track).

 

[Poodles]

PCV vapor will make it's way down to the filter...

Now, on cleaning the AFM. If you pull the electronics, don't loose the o-ring that seals the back temp probe (the front o-ring is captive on the vortex generator). Once the electronics are out you can clean the hell out of the housing. Make sure not to damage the honeycomb at the front.

DISCLAIMER: If you do this next part wrong, it's your fault if you break the AFM!

Now, you can (carefully!) use rubbing alcohol to clean the vortex generator and the temp probe. Do not get anything into the holes where the sensor is! Mine had quite a bit of buildup on the front of the vortex generator, which would probably throw the signal off.

Once it's all clean and dry, reassemble (don't forget the o-ring!) and you'll be good to go.