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Hi I recently purschased a 2006 cobalt ss 2.4 non supercharged, the guy we bought t from explained here was a cel on and it was pulling a code for bank one running to lean, i thru it on a scanner my friend has and pulled the same code the guy said he has had it in the shop and they can’t figure it out he had car for 9 years starting at 40,000 km and it currently is sitting at 194,000 ! It is causing the transmission to shift hard from p to r and then from n to d and while accelerating from first to second gear auto ! Now I have looked at the maf it looks clean and no obstruction filter is clean I looked at all the wiring to the maf and o2 sensor all look good! So I am wondering what other procedures you guys would suggest to fix problem, car is in amazing shape , motor doesn’t miss a beat, from my research the transmission is doing this cause d by this code, and recently the tc light has come on with a code stating system off, that information incorrectly stored! Any help would be greatly appreciate!
If it is having to add fuel to bank 1 that is what's setting the code. Look for any vacuum leaks in that area. Vacuum leaks get corrected with more fuel. The 2 together cause a high idle and harsh low RPM shifts.
If it is having to add fuel to bank 1 that is what's setting the code. Look for any vacuum leaks in that area. Vacuum leaks get corrected with more fuel. The 2 together cause a high idle and harsh low RPM shifts.
it doesnt seem to have a high idle, and it’s a hard shift whether low speed or you accelerate hard, and do you happen to have a diagram of the vacuum lines ?
Just to clarify P0171 is the only code you have correct? In my experience with these cars small vacuum leaks don't let in enough air to cause a lean code. Also being a 2.4 NA one of the only places you can have a vacuum leak is if your intake manifold was leaking because it was cracked or not sealing against the head. Which if you haven't taken it apart I woulnd't assume it was leaking between manifold and the head. You could also have a leak around your injectors or injector isolators. If you haven't had your injectors out I wouldn't assume that to be leaking either.
It's possible your MAF sensor could be reading incorrectly. Wouldn't hurt to use some MAF sensor cleaner and spraying it down. Don't use anything else.
It's also possible one or more of your of your injectors isn't spraying as much fuel as it should but before I would even consider that I would test the fuel pressure. If fuel pressure is low at idle or especially under load you could have a clogged up fuel filter or fuel pump on its way out. Fuel filters are cheap and easy to change and would be worth doing whether it is the cause of your fuel code or not.
You can narrow down what is causing your lean code by observing your life fuel trims with an OBD scanner. If you have high fuel trims at idle (STFT + LTFT =20% or greater) it is most likely a vacuum leak. If you have high fuel trims under medium load but not into PE you could have a fueling problem, either fuel pressure or injectors.
Edit:still don't think your lean code has anything to do with the hard shifts but I also don't have an automatic nor am I familiar with them.
Any chance someone altered the shifts with a programmer?
Take a look at the MAP sensor and its connections. I would expect a code if it was wiring but if it is not seated in the manifold all the way it can leak and low vacuum will command a harsher shift.
Just to clarify P0171 is the only code you have correct? In my experience with these cars small vacuum leaks don't let in enough air to cause a lean code. Also being a 2.4 NA one of the only places you can have a vacuum leak is if your intake manifold was leaking because it was cracked or not sealing against the head. Which if you haven't taken it apart I woulnd't assume it was leaking between manifold and the head. You could also have a leak around your injectors or injector isolators. If you haven't had your injectors out I wouldn't assume that to be leaking either.
It's possible your MAF sensor could be reading incorrectly. Wouldn't hurt to use some MAF sensor cleaner and spraying it down. Don't use anything else.
It's also possible one or more of your of your injectors isn't spraying as much fuel as it should but before I would even consider that I would test the fuel pressure. If fuel pressure is low at idle or especially under load you could have a clogged up fuel filter or fuel pump on its way out. Fuel filters are cheap and easy to change and would be worth doing whether it is the cause of your fuel code or not.
You can narrow down what is causing your lean code by observing your life fuel trims with an OBD scanner. If you have high fuel trims at idle (STFT + LTFT =20% or greater) it is most likely a vacuum leak. If you have high fuel trims under medium load but not into PE you could have a fueling problem, either fuel pressure or injectors.
Edit:still don't think your lean code has anything to do with the hard shifts but I also don't have an automatic nor am I familiar with them.
ok thank you I will do these test! I can check my fuel pressure using an obd scanner ?
Any chance someone altered the shifts with a programmer?
Take a look at the MAP sensor and its connections. I would expect a code if it was wiring but if it is not seated in the manifold all the way it can leak and low vacuum will command a harsher shift.
As far as I know no the guy we bought from bought it 9 years ago at dealer and it was his wife’s daily driver , he said codes always been on and shifted hard and had it in and out of shop and they couldn’t figure out the cause, so idk what to think on that!! The motor doesn’t skip a beat runs solid I will definately check these options out
No I think you will need a fuel pressure gauge that you connect to the schrader valve on your fuel rail.
ok will try these options!! As for the fuel pump I remember the guy saying one fuel line cracked so he had the whole pump and everything replaced , but he said the car has had this code since he bought vehicle and no shop could figure it out!! So I will do these things you provided and see if it helps
Any chance someone altered the shifts with a programmer?
Take a look at the MAP sensor and its connections. I would expect a code if it was wiring but if it is not seated in the manifold all the way it can leak and low vacuum will command a harsher shift.
as I recall the guy we bought from just had the map sensor replaced on the vehicle !
If the code started showing up after that it could have a leak. Check your fuel trims at idle
and as far as I know he’s had code since he got it he said and shops couldn’t figure it out ! then got a code for the map sensor so had it changed this is what we were told when buying
I assume those fuel trims are at idle given the 891 RPM. Those fuel trims are quiet high meaning it is making adjustments via the rear o2 sensor you are either intaking more air than it is calculating via the MAF sensor. This could definitely indicate a vacuum leak though I would think it would raise your rpms. HGT or someone that knows more about open and closed loop could probably clarify.
I assume those fuel trims are at idle given the 891 RPM. Those fuel trims are quiet high meaning it is making adjustments via the rear o2 sensor you are either intaking more air than it is calculating via the MAF sensor. This could definitely indicate a vacuum leak though I would think it would raise your rpms. HGT or someone that knows more about open and closed loop could probably clarify.
yes this was at idle! It’s just the freeze frame from the obd scanner ! And if someone can help me that would be amazing so frustrated
ALso thru another code being p1174 along with p0171 if this can help out I have no rough idle starts up no problem so I’m not thinking injectors , I have sprayed around the intake and that watched for change in rpm and nothing ! I have cleaned maf tool intake if to throttle body tightened up all bolts on intake and valve covers! Made a good deal to the air intake ! It’s all stock !! Only thing I can lean towards is a faulty o2 sensor or pin hole in exhaust manifold, did research and some forums saying that there is a bulletin for injectors needing to be changed and reprogram tcm , if any of this helps at all, I have to unfortunately take it on a highway drive today but hoping to pull it into shop tmrw and do some work checkin g exhaust etc
ALso thru another code being p1174 along with p0171 if this can help out I have no rough idle starts up no problem so I’m not thinking injectors , I have sprayed around the intake and that watched for change in rpm and nothing ! I have cleaned maf tool intake if to throttle body tightened up all bolts on intake and valve covers! Made a good deal to the air intake ! It’s all stock !! Only thing I can lean towards is a faulty o2 sensor or pin hole in exhaust manifold, did research and some forums saying that there is a bulletin for injectors needing to be changed and reprogram tcm , if any of this helps at all, I have to unfortunately take it on a highway drive today but hoping to pull it into shop tmrw and do some work checkin g exhaust etc
Well update made it to city where appointment was 2.5 hour drive and pulled codes my map sensor code came up apparently previous guy had it replaced is it possible that’s all the problem is is my map sensor ?
Freeze Frames are captures of the available data perimeters the second the code is set.
I notice a couple things.
Your long term fuel trim has been having to add a lot of fuel and is almost maxed out.
Your engine vacuum is very low... only 10hg. I mentioned earlier that your map sensor may be leaking or not completely inserted. That would cause a vac leak commanding more fuel and show a low reading as it is. I would watch the pre cat O2 and spray some carb spray around the manifold and map sensor looking for the O2 V. to jump up when you hit the leak.
