AFR goes lean when fan kicks in? PL Files...

[GangsterMD]

Hi guys, I was playing with my car in the garage working other bugs out... when I realized it wasn't idling very good. So I plugged in the laptop and realized whenever the fan cut in the air fuel went up to 15's and 16's - and it starts running crappy. Then when the fan cuts out the AFR goes down to low 13's and it idles nice. Then I remembered I had upped the fuel pressure the other day when checking things over as it was low. However I wonder it it's running rich now as when the fan is not on, and you touch the throttle it stumbles a bit. However when the fan is on, and you touch the throttle it perks up nicely. I would really like some advice on this. I've attached 2 idling snapshot powerlogger files.
Thanks
Darren

 

[novaderrik]

maybe the electrical load from the fan is dropping the system voltage, which slows down the fuel pump and makes the spark weaker.

 

[1fast6]

maybe fan wash?

 

[Pittsburghkid]

I can't see the snapshots but are you getting good voltage on the tps sensor with the fan on?

What fans are you running? Stock? Dual? other? If aftermarket, does the fan have a separate relay to handle the extra load?

 

[TurboDave]

It's definately odd, how your system voltage drops at fan cut in. It drops for a very short period of time and quickly recovers, which all appears normal, but the car stays lean. Even though you're in open loop.

 

[Chuck Leeper]

Get it to occur, again. Then, check voltage at the pump....

 

[GangsterMD]

Thanks for the help guys. I have GBodyParts.com's dual fan setup with relays. Thought about fan wash but IAT sensor is in the maf pipe and intake air temp doesn't change. From what I can see fuel pressure transducer does actually show increase of about 1psi when fan kicks in? Which should be due to the corresponding drop in vacuum right? I have the Casper's TPS voltage enhancer, and the fuel pump is hot wired. Let me know if you need anything else?
Thanks again.

 

[Jerryl]

Deleted "Fan wash" post . . . looks like you already looked at that. :redface:

 

[mikestertwo]

Is Psi4 fuel pressure? I'm only seeing 23 psi.

 

[GangsterMD]

Hmmm... Mikester that's interesting as I'm seeing 35 psi on the display - and the guage on the dash I'm pretty sure is displaying the same.

 

[TurboBob]

to read other peoples data (like the fuel pressure) you need to configure your PLC software like theirs.

As far as a lean idle when the fan kicks on, that is very typical for fan wash.

(you said you have a powerful fan, so its not surprising) Do you have a cold air kit, or are you drawing in underhood air?

Bob

 

[GangsterMD]

Fan Wash?

Hi Bob. I do not have a cold air kit. Since my iat sensor is in the maf pipe before the maf sensor, and the iat didn't seem to change I didn't think that was it. But there's probably more to it than that?

 

[WSLN 6]

Unplug your fans and see if it does the same thing when your fans "should" be turning on.

 

[TurboBob]

Hi Bob. I do not have a cold air kit. Since my iat sensor is in the maf pipe before the maf sensor, and the iat didn't seem to change I didn't think that was it. But there's probably more to it than that?

its not the temperature, its the turbulence.

Bob

 

[GangsterMD]

Well that's good news I guess Learn something new every day. Thanks Bob.

 

[TurboDave]

Hi Bob. I do not have a cold air kit. Since my iat sensor is in the maf pipe before the maf sensor, and the iat didn't seem to change I didn't think that was it. But there's probably more to it than that?

Your aircleaner is way out on the edge and well past the radiator. I would think that fan wash should not be an issue on yours. My aircleaner sits way out there like that also, and I don't see a fan wash issue.

I also have a fairly significant voltage sag for a second when the fans turn on, but no air fuel ratio change of any consequence and it certainly doesn't stay that way.