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View Full Version : P0174,P0171 Codes...

Wicked
03-18-2005, 08:01 PM
I have been getting codes for lean condition on both banks. The codes are triggered by long term fuel trims of over 20%.

After I put the supercharger on, my car ran great for a long time and it still does.

I guess it was about 6-8 months after adding the charger that I started getting the P codes for lean condition on both banks. The PGM I borrow from work shows a snapshot, it looks nearly identical everytime....same speed, tps, rpm, etc. The conditions I remember off the top of my head are 1800rpm, 50-something mph, 5th gear. I forget the load, TPS, etc but they all seem normal. By definition of the codes, my long term fuel trims are over 20%. I believe it happens in the contructions zones of I20, the only place I'd be going 50mph(my speedo is off so its actually 58mph)

I originally thought it was related to an exhaust leak on the driver side. But I fixed my exhaust leak, then got the code again, this time for both banks.

I have tried different O2 sensors with no luck. I also tried disconnecting my Air/fuel gage to make sure it wasn't creating an error in the O2 signal. Even if it had been it would onyl affect one bank anyway.

I guess the only other thing that may have changed is MAF position. I guess its possible that at that specific RPM/airflow the MAF gets confused.

I'm planning to get the car tuned soon hopefully and I want to clear up any items that might screw up the tunability.

Any ideas?
Wall96cobra
03-18-2005, 08:22 PM
sounds like a vacuum leak to me
uvbnhad
03-19-2005, 01:32 PM
before you rack your brain and all that have you tried the simplest thing and unplugged your battery for a bit? After you did some stuff it might not have reset the computer and cleared the code. Just a suggestion before you really start diving in. I've seen it clear up several times before. Of course I could be wrong.


EDIT: Not saying this will absolutely fix your problem. Just might be worth trying before you really dive into trouble shooting.
Wicked
03-19-2005, 04:30 PM
sounds like a vacuum leak to me

I tried that. Haven't found any vacuum leak. I originally thought it might be related to the PCV system at first since it WAS a big vacuum leak. But I have that fixed now so I'm pretty sure thats not it. I thought that at first I looked all over for possibilities and not finding anything. Might be worth another loook though, just looking for other possibilities as well.

Interceptor, I have tried many changes and have disconnected the battery(usually overnight) everytime to reset the Keep Alive memory. Still keeps coming back.
Wicked
03-20-2005, 02:07 PM
I checked the vacuum line to my boost gage and the vacuum line to my bypass valve and neither is leaking.

I think the only other thing is the idle air bypass, I may have taken that off once before. I will check it with some smoke to see if it leaks.
CrimsonRacing
03-20-2005, 02:43 PM
speaking of codes.........

I pulled mine yesterday and returned 4

186-MAF injector pulsewidth voltage too low

157-MAF sensor voltage too low

could these be caused by the C&L?

The other 2 have been corrected.
Wicked
03-20-2005, 07:44 PM
Dirty MAF element?
Wicked
04-07-2005, 05:30 PM
I checked the vacuum line to my boost gage and the vacuum line to my bypass valve and neither is leaking.

I think the only other thing is the idle air bypass, I may have taken that off once before. I will check it with some smoke to see if it leaks.

I replaced the IAC gasket and it didn't solve the problem.

Only other thing that has changed along the way is the MAF position. I think this is the next place I will look.
Wall96cobra
04-08-2005, 06:31 AM
Hey Brad did you ever hook up the extender? Do you think you're still pegging the maf?
86GT
04-08-2005, 10:27 AM
Reseting the EEC is not a good idea in my opinion. You need to find the cause of the fault, not just reset it and then let it come back. If the problem cures itself or if you find the problem the code will disapear. I believe on the EEC-V systems it takes a sample of ten and if two fail it will throw the code. It keeps doing this even if the code has already been set. This is so it can unlatch the code if the problem goes away.

Do you have a tuner of some sort(Tweecer, EEC Tuner) that can datalog? If so you can do a couple of runs to find out where the 20 lean condition is occuring. If it is at WOT or so on.

Other mechanical areas to check would be a leaking EGR or exhaust manifold gasket. The exhaust gasket are the hard ones to determine. It gould be a small leak that you can not hear.

Wait a minute, I just read that it was both side. This leads me more to the EGR. The MAF element could be dirty or just plain going bad. Chargers may shorten the life of the MAF electronics due to the temperature increase. The early MAF failure thing is just my opinion.
Wicked
04-08-2005, 10:26 PM
Hey Brad did you ever hook up the extender? Do you think you're still pegging the maf?

Nope, waiting for a tune. Its wired in but has the dummy coupler in place.
The problem is not related to peggging maf as it occurs at low rpm, low load, cruising.

86GT, I agree about the exhaust leak/both banks not being the problem.
I am thinking the MAF is a possibility. I can look at the EGR, but I have never messed with it on this car.