The reason I said tune earlier, there is a map with IAT and ECT multipliers in that increase the fuel by given amount based on temp. So with it being cooler outside now you may be dipping into a larger multiplier in that map which is causing the car to have to add/subtract over 20% to get to stoich. That will throw a 0171 code, it is probably IAT since the car will be open look during warmup. This is just something to check, but also check for air leaks.

 

Ahhh, now the car isn't throwing any codes! LOL Went to start it up yesterday and no codes, driven it around town several times, with nothing happening.


The weather has been mild around here (Dallas,TX) too, even when the code did come up, so I'm pretty confused....

 

I would lean to a multiplier table in the tune then. A vacuum leak does not fix itself, and if it is outside temp related, then that is path I would look at. I am sure the history code it there, but it just means that you are dipping into and adder or multiplier table that is taking you over the threshold and reporting an issue. What are you LTFT's

 

sounds like an air leak after the MAF to me, if your stuck thinking its an 02 Simple test then take them out and swap them side to side and reset the codes. if it comes back on and its still the same side issue then look elsewhere.

while looking at your scanner data look at your sensor readings to see if its passing back and forth lean to rich at idle, cruise speeds and 3/4 throttle. The sensor voltage should go up and down alot switching from lean to rich in most conditions except full power.

best way to test an 02 is with an oscilloscope, but they are easy enuf to swap out..
Side note: if you elemenated the back to 02's why dont you just swap it to the front

 

I also live in the Dallas area and Sunday I had my CEL pop on and I ran a diagnositics. Got a P1011 code thrown and the P0171 code as pending. The P1011 code is an air flow performance code. I thought maybe something got stuck in the bottom air intake or the filter was dirty. So I took of the Killer Bee CF and the filter, checked the TB, checked under the car. Everything looked fine. I put it back together and reset the CEL and drove again tonight. The car felt like it was missing at hwy cruising speeds. Ran another diagnostic and got the P0171 and P0174 as pending codes again, but not yet thrown to activate the CEL.

The point here is this didn't happen until the weather cooled considerably. I have a QM600 cam and headers with a tune. Carlos retuned my car this summer to smooth out the daily driving and it was wonderful and great...LOVED the new tune. But when this happened the other day...out of the blue, I wondered if it could be the cooler denser air causing the issue.

So, I reset the codes again tonight after getting to work. I am going to switch over to my HPTuners and log the drive home during the cold morning air and see what we get. I'll send it to Carlos and see if there is something going on in the LTFT. I suspect the reason given above about the LTFT and dipping into another part of the map is the reason this is happening. May need a different tune for the cold weather.

Jay

 

Please let me know how that goes.... my car hasn't had the CEL pop since, no issues. I maybe have a very slightly rough idle, but that's about it, I think you're talking abour the "surging" with your cam, are you an automatic?

 

Bingo, this is what I have been trying to explain if there is no air leak.
You will not need a new tune or a whole tune anyways, you just need a adjustment to a ECT or IAT table. He should be able to fix this easy.
Thanks

 

This is really amazing. At the end of the cooler air season in the late Winter or early Spring I started getting P0171 and P0174 codes and was able to reset these with my scanner. They always came back and seemed very temperature dependent. When it warmed up a little my car stopped throwing codes. It did not throw any P0171 and P0174 codes all summer. Just over the past couple of weeks when the air temperature dropped in the 40's to 50's the codes came back again. I just finished resetting them the first time this season. Here we go again.

It is really wierd that we have several people seeing these codes with the cooler temperatures. I live in Virginia.

 

It's not weird -- it's chemistry. Cooler air means denser air. Denser air means more oxygen. More oxygen means you need more fuel. If you run out of range and can't add enough fuel, you throw a lean code.

 

Is it dangerous to run lean in the cooler temperatures or should I take it back to my tuner and have him make some tweaks in the tune? I always thought running lean was not a good thing.

 

Running lean is bad. A retune is in order to correct.

 

This may be a simplistic answer, but another similar post with both the P0171 and P0174 codes had duct tape as a solution.

I tried it and it works. On the 08 when a gap develops between the radiator cover and the front cross bar, the turbulent air flow can throw the codes. That thread has some nice photos and I think that there was a TSB on this subject as well.

I taped up the gap and a few small holes with a home depot special black super adhesive gorilla duct tape. The color matches the plastic, I cleared the codes, and they have not returned.

 

logically you are correct, but you are wrong as when it comes to the lean code. These cars are very smart, not just Corvette's but the electronics.
The MAF sensor reads the incoming air, it know's how much air is entering the engine. The MAP sensor knows how much pressure there is and it bounces the two off of each other. The IAT knows the temp and it add fuel according to a table based off temp. No matter the changes outside the ECM accounts for those. There are two things that can cause this without a special set of circumstances. One there is a vac leak somewhere and the engine is breathing extra air that is not being measure by the MAF. Two is in the tune, he could have an adder or multipler table that is off and it is why it is only happening a certain temp, this latter is what I think is wrong with it. Anyways any tuner should be able to figure this out when they log the car.

 

Do a search for the following thread:

Service Bulletin 08-06-04-040

May not apply in all cases, but it is safer than chasing the cause of the problem by messing with the mixture.

 

Exactly correct.

Since all these tables are out there and available to be messed with, some tuners will change the hack or rape a table. The most common one to change is the PE table. Some engine with lots of mods should have a complete re-tune that includes PE, MAF, and VE tables.

But some tuners don't want to take the time to do that, so they will simply change the PE table to get the desired A/F ratio at WOT. They will command 10.5 to get the injectors to deliver enough fuel to have an actual 13:0. Seen that happen for real.

When not in WOT, the LTFT% table will try to make the adjustments. If the VE and MAF is so out of tune, the LTFT% will be all over the place and could throw a code if its off by 25%. That's not that far out of bounds. I had a loose vacuum hose, and it was off by 25% and threw a code.