Why do I run EXTREMELY lean when I get up to operating temperature?

[DSMTyson]

Alright, I've been having trouble with my car running REALLY lean. I'm going to try to desribe it as best I can. All the a-f ratios are give or take .5.

When I first start up my car. The o2 will cycle between 12.9-14.3. Normal for the temps outside. And it will gradually get leaner as I get close to operating temperature while cruzing. At 140*, it cycles at 14.7-16. When i get to operating temperature it will all of a sudden switch from cycling at 15-16.7, and go to 16.7-18+++. Then after some more driving It will cycle from 17.5-the wideband not even reading anything because it goes so lean. Even after I fixed a boost leak and reset my fuel trims.

Now, I have ruled out the following: exhaust leak(I can feel the power leave when it goes lean, and it misses), clogged fuel filter/fuel strainer, fuel pump going out, coolant temperature sensor.

When I give it 3/4+ throttle it will switch to my open loop a/f ratio, which is 11.3. But when i cruise in open loop it will go lean just like it would in closed loop, then when i give it some"lead foot" action it will go to 11.3(normal).

Now the longer I cruise, the leaner it gets, no matter what. I am cunfused. Coolant readings are acurate. I reset everything on DSMLink back to stock values and it is still doing the same thing.

 

[UofACATS]

Can you post a log please?

 

[91stocker]

Sounds like IAT heat soak.

 

[Jst4Cyl]

Boost leak? I've seen FMIC's do this when cracked. Sounds like its expansion from the introduced heat the car creates.

 

[DSMTyson]

Can you post a log please?

I would post a log, but my laptop wont be fixed until friday.
------------------
I'm still using a 2g maf, so an IAT sensor is out of the question.
------------------
I thought it would possibly be a boost leak. But how could a boost leak make me run lean? I always thought that a boost leak would make me run rich because metered air is leaking. Therefore, there is less air for the same amount of fuel.

Please correct me if I am wrong.

 

[91stocker]

I would post a log, but my laptop wont be fixed until friday.
------------------
I'm still using a 2g maf, so an IAT sensor is out of the question.
------------------
I thought it would possibly be a boost leak. But how could a boost leak make me run lean? I always thought that a boost leak would make me run rich because metered air is leaking. Therefore, there is less air for the same amount of fuel.

Please correct me if I am wrong.

Ah gotcha, i seen v3 so i assumed SD

 

[DSMTyson]

Ah gotcha, i seen v3 so i assumed SD

Nah, you can go either way with it. I hope to be going SD this summer.

BTW I just did: new o2 sensor, plugs, and wires.
____________________________________________

Any ideas of what i should check? Besides Fuel pump strainer, fuel filter, fuel pump.

 

[zdravko_k2002]

My car was just doing something very similar to this but in my case it would go lean and the car would bogg lose power and seemed like it was running on 2-3 cylinders and not be drivable any more i would have to shut off my car start it back up and hope that its not lean and drive it for a little while till it did it again and it pissed me off I checked everything injectors fuel pump leaks plugs wires all that bs and everything seemed good....untill I opened up my ECU. Long story short I had 2 blown drivers visibly they were browinish and little fried up so i sent my eprom ecu to ecmlink and they replaced the drivers and said few of my caps were bad fixed it all up for 60 bucks and car has been running like a charm ever since. Im not saying this could be your problem but its def worth checking out, because thats ### it was for me. Also if you have a stock noneprom ecu try to put that in with your stock injectors and see if it runs fine, mine def did so I figured it either had to be my ecu or injectors and it was the ecu, but let me know what you find and how everything turns out.

 

[DSMTyson]

My car was just doing something very similar to this but in my case it would go lean and the car would bogg lose power and seemed like it was running on 2-3 cylinders and not be drivable any more i would have to shut off my car start it back up and hope that its not lean and drive it for a little while till it did it again and it pissed me off I checked everything injectors fuel pump leaks plugs wires all that bs and everything seemed good....untill I opened up my ECU. Long story short I had 2 blown drivers visibly they were browinish and little fried up so i sent my eprom ecu to ecmlink and they replaced the drivers and said few of my caps were bad fixed it all up for 60 bucks and car has been running like a charm ever since. Im not saying this could be your problem but its def worth checking out, because thats ### it was for me. Also if you have a stock noneprom ecu try to put that in with your stock injectors and see if it runs fine, mine def did so I figured it either had to be my ecu or injectors and it was the ecu, but let me know what you find and how everything turns out.

That is exactly what my car is doing. I'm going to check my ecu this morning. Thank you.

______________________________________________________

Dude, you are the ####ing man! I took my ecu out and opened it up, and sure enough, I had multiple caps that were leaking. I'm going to have to send it in to ECMLink.

 

[zdravko_k2002]

Hey man Im glad I can help you out my car was driving me crazy for about a month left me on the side of the highway multiple times it was just getting so annoying I was so angry I even posted my car for sale but after figuring it out and fixing it all up she runs like a champ now Im glad you figured out your problem sometimes it just gets frustrating after you have checked everything and you still cannot find a solution to your problem I know how you was feeling thats why when I saw the title of your post i was like let me check this out , but get that ECU fixed and when you get it back and put it back in PM me and let me know how the car runs and if it fixed your problem I hope it does and most likely will but still let me know gotta keep these rare vehicles on the roads and not inside the garage you know what I mean )

 

[DSMTyson]

Hey man Im glad I can help you out my car was driving me crazy for about a month left me on the side of the highway multiple times it was just getting so annoying I was so angry I even posted my car for sale but after figuring it out and fixing it all up she runs like a champ now Im glad you figured out your problem sometimes it just gets frustrating after you have checked everything and you still cannot find a solution to your problem I know how you was feeling thats why when I saw the title of your post i was like let me check this out , but get that ECU fixed and when you get it back and put it back in PM me and let me know how the car runs and if it fixed your problem I hope it does and most likely will but still let me know gotta keep these rare vehicles on the roads and not inside the garage you know what I mean )

I can only imagine if this was going on for a month with no avail. 2 weeks had me pissed off, scratching my head, and cursing at my car for being a bi*** . Thanks again. I'll pm you when i get my ECU back and let you know whats going on.