tording99Z28

iTrader: (3)

Hey guys. So I have a dilemma that has been going on for like 7 months now. I have the turbo car in my sig. I have been having problems where after the car gets hot from running it starts running lean on me. I have narrowed it down to the ECM as I have discovered that when the lean condition starts happening if I take a box fan and put it on the ECM within a couple minutes the AFR comes down to 14.7 like it should. Turn the fan off and a couple minutes later it starts creeping up. Has anybody ever heard of something like this? I have tried 2 ECM's and they both do the same thing. How can I relocate the ECM to behind the dash? I have no HVAC at all so I have an HVAC delete plate over the hole but the harness for the ECM connectors is not long enough to reach all the way into behind the dash. Any ideas or thoughts or suggestions?

Cam72aro

iTrader: (28)

Can you post a data log showing what it's doing when this happens? I am curious if the commanded afr is changing, or an input is telling the PCM to change fueling. Include map, injector on time, tps, coolant and iat. Also o2 voltages, etc.

tording99Z28

iTrader: (3)

Sure I can do a fresh log right now. You want it to be an open loop or closed loop? It happens in both, just takes longer in closed loop for the AFR to start going up because the ECU does adjust for the lean condition when it starts happening. Once the STFT's hit 50.8% and the ECU can no longer adjust for the lean condition then the AFR starts rising.

necrocannibal

iTrader: (5)

Off topic and kind of a hi jack and deeply apologize but I really like that front piece you have. Did you buy that somewhere or make it yourself? I'd like one of those on my turbo SS.

tording99Z28

iTrader: (3)

This is a perfect example of what I am talking about. Scroll over to 20 minutes into the log and you will see the short term fuel trims start going up to 50.8% and then once they max out the AFR will start going up. If I put a box fan on the ECM while this is going on the STFT's start dropping and so does the AFR back down to 14.7:1. I tried to attach my cfg file but it is not an approved extension here on tech. I can email to you if you want it.

code4

iTrader: (30)

move your iat sensor out of the engine compartment & see if it goes away.

tording99Z28

iTrader: (3)

Not sure exactly what you mean or how to go about that. The wire is only so long and I can not move it very far out of the engine compartment.

code4

iTrader: (30)

extend the wires if you have to, iat heat soak will cause a lean condition that will drive you crazy. pull it from your intake pipe & let it hang down out of the heat & see if your problem goes away.

I have had to put the iat right at the outlet of the A2A intercooler or run two IAT's, it sucks.

tording99Z28

iTrader: (3)

Any idea why a fan on only the ECM then and no other part of the engine corrects the problem? If it was IAT heat soak I would think cooling the ECM would have nothing to do with it.

Also I have been having this problem back into last winter when it was cold out and the IAT temps were like 60 and 70 degrees max.

SPRAYED 01

iTrader: (22)

How do you run 2 iat sensors? Honestly this makes no sense. There are no sensors to cool in the ecm. Any chance the fan is cooling off some thing else at the same time?

tording99Z28

iTrader: (3)

This is possible and likely. To try and detect if it it really is the computer tonight I isolated the computer by pulling it out of the little cubby hole and wrapping it in a blanket and then I used some foam to wrap around it. I then put the fan back on the passenger side back by the firewall and again with the fan on the AFR corrected and came back down to the 14 range where it should be. With the ECM wrapped in a blanket and foam I don't think any of the air from the fan was hitting the ECM so what else is back there in that little area that air from the fan could be hitting causing the fueling to be corrected? I checked the IAT temps and they stay the same with the fan as without so I do not think it is IAT related at all.

Cam72aro

iTrader: (28)

The map sensor reading looks low. At idle your map reading is around 50 or less. I know my car with a 3 bar gm map sensor on it idles around 70. During your run at 16.25 into the log you hit 170kpa or 10psi. Timing is at 20 degrees and afr was reading 12.95 on the wideband, scary. Can you verify the map sensor is reading correctly? It seems low to me. Is the car set to make around 10-11 psi?

Old Geezer

iTrader: (3)

Fan flow on the O2 sensor[s]??

98Camarod

iTrader: (43)

Is the fan externally powered or off of the car that your using? What's the voltage when this happens?

98Camarod

iTrader: (43)

Have you tried just running it OLSD to see if the problem persists? It also looks like when it gets over 217* the STFT's get worse and then reach a max of 225*.

tording99Z28

iTrader: (3)

Yes the car is set to make around 10-11 psi with the spring I have in the gate. The tune needs a final tweaking on by my tuner but I am trying to remedy this hot lean condition issue before I take it to him and spend another $200 for more dyno time. I believe the MAP sensor is working correctly but I really don't have a way to test it. If my MAP is lower than yours then doesn't that just mean my car is pulling more vacuum at idle than yours is?

tording99Z28

iTrader: (3)

Would fan flow on the O2 sensors affect them reading the exhaust gas in the header? They are C6 corvette headers so the O2 sensor sits right on top of the header.

tording99Z28

iTrader: (3)

Externally powered from my garage. Just a standard old box fan.

tording99Z28

iTrader: (3)

Yes the tune I have loaded into the car right now is actually OLSD. It is actually worse in OLSD because the ECM does not correct for the lean condition at all so the WB O2 gauge starts showing a lean condition much sooner. I thought the temperature was related like that at first also but it is not. I have some other logs where it starts happening and the ECT is only 205 and by the time the ECT hits 209 the STFT's are maxed out. I think it depends on the temperature of the air that day. When it his hotter outside the ECT goes up quicker so it is higher when the problem starts occurring than on a day where it is cooler like 80 degrees.

Cam72aro

iTrader: (28)

It does, just interesting how much lower.
The os is a 3 bar sd, right? How is the maf failed in the tune. I know that can cause weird things. How new are the o2's? I know they are showing lean because the car is lean, but are they the reason the car is going lean. I have had o2's do some downright weird stuff. What map sensor are you using? What about a vacuum leak that only shows when really hot?
Just throwing ideas out there and thinking out loud.