Troublesome Trouble Codes... P0171

[aaron97]

Do yourself a favor, save a bunch of time and just delete them. I only had one bearing leaking, which was the rear passanger side, and it threw both codes. I wouldn't really trust the skateboard bearing, but I hope it works out for you.

I dont want to delete them just yet and there are two reasons for that, one is its not me doing the work because i am stuck overseas and second last time i checked ECU retunes start at $250 and up. I dont want to pay $250 just to end up having to pay it again in a few months when its really going to need a retune after all the mods are done. Future plans include a supercharger, so I will eventually be doing the delete, but for now I just need the car to pass emissions and be a good daily driver for my friend to use and maintain while i am over here.

 

[aaron97]

Well, the Fuel Pump is in and the pressures are all good now, but the 171 and 174 are still there. So now i am looking into what its going to cost me for the retune for the IMRC delete. Only thing left it can be is them bearings. If i do the delete and those darn codes are still there, then i give up until i can get back to the states to take car of it myself.

 

[FunkyBoss]

It could be hit or miss on the factory tune, I guess I've just been lucky not to get a CEL. I'm 99.9% sure it's you bearings. Again, I fought this same problem for a year and the only reason I found the leak was because I was pouring water near the intake to dilute ALOT of spilled fuel, and could hear the water being sucked in through the bearing. Did your buddy try the silicone sealant?

 

[aaron97]

It could be hit or miss on the factory tune, I guess I've just been lucky not to get a CEL. I'm 99.9% sure it's you bearings. Again, I fought this same problem for a year and the only reason I found the leak was because I was pouring water near the intake to dilute ALOT of spilled fuel, and could hear the water being sucked in through the bearing. Did your buddy try the silicone sealant?

No, he already picked up some new sealed bearing and is going to try changing them out this week and see how that goes.

 

[aaron97]

Well, no good news yet guys. He changed out all the seals and IMRC bearings and they are working out good and are not leaking at all now. But the codes are still there and now the car wont idle properly. Installed a new IAC since the old one was gummed up and that didnt help, installed a new TPS and that didnt help either.

We're running out of things to change/clean/fix/inspect. At this point we are going to replace all the old vacuum lines with some new rubber ones. We did a pressure check on the system and it wont hold pressure, so its either got cracked/broken lines or bad components that the lines go to. But since the rubber hose is cheap, we will start there.

Other than that, only things left to change are EGR (valve, vacuum solenoid, and pressure monitor), air/smog pump, fuel injectors.

He is going to replace all the o-rings on the fuel injectors this time, since he has to pull in intake again to replace all the vacuum hoses and to make sure something didnt happen or get over looked on the last install, which might cause the idle problems.

 

[Tx_Diablous]

Dude, I know it sounds far fetched....but I have seen it work. Put a 1/4 inch spacer on the O2 sensors and see if it goes away...I would have not thought it would work either but I saw it with my own eyes.

:shrug::shrug::shrug:

 

[STAMPEDE3]

What did you set the TPS at?

and please tell me you unhooked the battery for a few minutes after changing all this.

 

[aaron97]

What did you set the TPS at?

and please tell me you unhooked the battery for a few minutes after changing all this.

Well, he changed all the vacuum hoses and also fixed all the broken pieces on the fuel injectors. Now the idle is back to its usual self. Its not fixed, but at least its back to its old ways. Which is, when you let off the throttle the rpms come down to about 1500 and sit for a few seconds before coming all the way down to idle. He tells me, after all the work he's done that the rpms come down faster and it doesn't sit at 1500 for as long as it used to.

As for the TPS, i dont know what it was set at, since i wasn't there and doing the work. And as for the battery. He disconnects it for all maintenance and after every time he changes a major part he does a complete system reset so that we can be sure of when the P0171 and P0174 come back its not just left over from before.

He found a leak at the rear right side of the intake where the upper and lower meet and is going to take it all back apart today and try to fix it for the last time. By now he must be a pro at removing and reinstalling the intake system.

 

[aaron97]

Dude, I know it sounds far fetched....but I have seen it work. Put a 1/4 inch spacer on the O2 sensors and see if it goes away...I would have not thought it would work either but I saw it with my own eyes.

:shrug::shrug::shrug:

But that's not a "fix" to me, we shouldn't have to shim the sensors to get the CEL to go away (unless the new sensors were longer), the system should work the way its supposed to work. But i guess, as a last resort to pass emissions we could try it, but i would still want to find the real culprit.

You know guys, this may seem odd, but is there any way not having cats could cause a Lean condition? I was going over it in my head and dont think it would, one because the ECU should detect the Lean condition and simple adjust the fuel map to fix the lean condition, and second, because i ran around for 4 years in my '97 GT without cats and never had a problem like this. I have a new SLP catted x-pipe going in this week (because i need the car to be emissions legal again) and when it gets installed he is going to check the exhaust manifolds for cracks and replace the gaskets as well, just to be sure they are not the problem.

 

[STAMPEDE3]

Very well could be exhaust leak in front of O2s.

 

[aaron97]

Very well could be exhaust leak in front of O2s.

Ya, that's what i originally thought when it was just the Bank 1 code being tripped, so it was the first thing we looked at. But there was no signs of a leak, even though its tough to get in there to listen and look. But after changing all these parts, its been both Bank 1 & 2 going Lean now. I just wish i was there to be doing all this myself, not that i dont trust my buddy but it hurts my pride to let someone else work on my car while i have to sit by and doing nothing.

 

[STAMPEDE3]

I had to find my leaks with my hand, Could not hear them.

Motor cold, crank it up and stick you hand up from the bottom and feel for air coming out.

Seafoam is another way I've found them in the past.
When it smokes it will come out of all leaks.

 

[aaron97]

Anyone ever heard of the Differential Pressure Feedback EGR (DPFE) going bad and causing "too lean" codes.?

 

[aaron97]

It just amazes me on how many things on this car were actually bad. We checked the DPFE and it was bad, put a new one in and rechecked it and the new one is good. That's just a habit we have (because we're aircraft mechanics) to check the new parts to make sure they work. I talked to my buddy and we went over a few things. The TPS was .98 and when he changed the IAC he said it took longer for the rpms to come down so he put the old IAC back in and the rpms come down faster. This is before we found out that you shouldn't put non-Ford brand IAC's on because they move slower. But either part, old or new, the rpms still hang up around 1500-1800rpm once the engine is warm.

He also went over what was happening with the codes. He cleared the codes then drove around, the P0171 was logged 3 times, all at idle speeds. It was 32 miles of driving before the P0174 was logged. The LTFT's where at 25% and RTFT's where 5%, which is the exact situations needed to trip the P0171 & P0174 codes. After researching some ford stuff, we found that most fords had a problem with these codes because the parameters were too strict and apparently some time around 2002 they released a PCM update to change this and give more of a tolerance. He is going to call the dealer today and see if he can get in for a PCM check.

A few other things we found and fixed are: the spark plugs were still gapped for nitrous use. And another thing he noticed was the fans turn on at 210*F when all the books say they shouldn't turn on till 230*F. As well as finding that the cover plate that covers where you would install a chip on the PMC was missing, so its possible that the PCM has been re-flashed. Which is another reason we're going to take it to the dealer to see. If the dealer cant do anything about it, we might just have to buy a new PCM just to be sure its at its stock settings.

He is also going to swap the injectors right to left, then drive around and see if the P0174 pops first, because its always been the P0171 to pop first. If the code swaps, the answer is obvious. Oh and we also made sure its still the stock 24lb injectors in there and not somethng else. But if the codes dont swap we're back to suspecting the PCM and who knows what else.

 

[aaron97]

Swapped the injectors, no change. P0171 still trips first and then a long time later the P0174 trips.

 

[mwolson]

I just noticed this this thread, and am throwing the same codes, but I know what is causing it in my case. My MAF transfer function is not properly calibrated. These codes are thrown when the PCM learning needed to keep the engine running at stoich in closed loop exceed a pre-programmed threshold, and the cause is often a wacked MAF transfer function in a tune.

The evidence that your car has been tuned is there due to the fan turn-on temps. Also, without the cats, you should throw a code, unless the rear O2 sensors were turned off in a tune. And you said something about nitrous...

If you can find anyone to stick an Xcal2 or equivalent on it, have them log your long and short term fuel trims. I think you will find them way off. If that is the case, you will need a new tune.

If it is, in fact, a stock tune, you should try a known good stock MAF sensor if you can.

As for my car, I also know that my PLX M300 WB has a very old O2 sensor in it, and I need to get time to get it replaced because I am also getting a fuel trim difference from bank to bank. I am using the NB output from the M300 to simulate the stock NB on the driver's side. Once I get that fixed, I just need to recalibrate the MAF transfer function. Fortunately I have the SCT PRP so I can do it myself. I am afraid you are going to need a tune...

 

[mwolson]

Oh, and I'd bet an SCT dealer could sell you a stock tune in a chip much cheaper than a dealer PCM would cost.

 

[aaron97]

I just noticed this this thread, and am throwing the same codes, but I know what is causing it in my case. My MAF transfer function is not properly calibrated. These codes are thrown when the PCM learning needed to keep the engine running at stoich in closed loop exceed a pre-programmed threshold, and the cause is often a wacked MAF transfer function in a tune.

The evidence that your car has been tuned is there due to the fan turn-on temps. Also, without the cats, you should throw a code, unless the rear O2 sensors were turned off in a tune. And you said something about nitrous...

If you can find anyone to stick an Xcal2 or equivalent on it, have them log your long and short term fuel trims. I think you will find them way off. If that is the case, you will need a new tune.

If it is, in fact, a stock tune, you should try a known good stock MAF sensor if you can.

As for my car, I also know that my PLX M300 WB has a very old O2 sensor in it, and I need to get time to get it replaced because I am also getting a fuel trim difference from bank to bank. I am using the NB output from the M300 to simulate the stock NB on the driver's side. Once I get that fixed, I just need to recalibrate the MAF transfer function. Fortunately I have the SCT PRP so I can do it myself. I am afraid you are going to need a tune...

I've already swapped the MAF to a new one. As for the cats, I haven't mentioned any problems because there are none. I have MIL eliminators installed and there are no codes from not having the cats. I have also already bought an SLP x-pipe that has cats and it will be going on shortly. And i didnt know about the nitrous until the past week, and even so the car hasn't had N2O on it for more than 4 years (because that's how long I've known the previous owner). But i had my suspicions, then when i found the holes in the trunk that match what a n2o bottle bracket needs, along with a toggle switch and relay that aren't hooked to anything. Then finding the plugs gapped to .35 is what finally convinced me. I asked the previous owner if he knew or not and he thinks he remembers the owner before him saying it did but wasn't sure.

Oh, and I'd bet an SCT dealer could sell you a stock tune in a chip much cheaper than a dealer PCM would cost.

Got off the phone with dealer and they said they can reflash the PCM back to stock and install all the updates for just under $100. So i have an appointment for that on Wednesday. Time is running out, i only have till March 8th to fix this problem and get it registered. If i cant meet the March 8th deadline the car goes to storage and wont get touched for a year or two, until i can get back to the states to do the work myself.

 

[aaron97]

These codes are thrown when the PCM learning needed to keep the engine running at stoich in closed loop exceed a pre-programmed threshold,.

Here is the info if you (or anyone else) wanted to see it. Its in relation to TSB 01-9-7 which effects all 1994-2001 Mustangs.

P0171 - System to Lean (Bank 1), Description: The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when he adaptive fuel tables reach a rich calibration limit.

DTCs
Lean: If the LTFT reaches Max, >25% and RTFT >5% - P0171 Bank 1 Lean: P0174 Bank 2 Lean

P0171 Possible Causes,
Fuel System:
· Contaminated fuel injectors
· Low fuel pressure or running out of fuel (fuel pump, filter, fuel supply line restrictions)
· Vapor recovery system (VMV)
Induction System:
· MAF contamination
· Air leaks between the MAF and throttle body
· Vacuum leaks
· PCV system concern
· Improperly seated engine oil dipstick
EGR System:
· Leaking gasket
· Stuck EGR valve
· Leaking diaphragm or EVR
Base Engine:
· Exhaust leaks before or near the HO2S
· Secondary air concern
Powertrain Control System:
· PCM concern


And as you may have read, the data logger we have will log what the DTC's at the moment they trip the codes. And what we found was data consistent to what it reads with the >25%,>5%. In all the TSB stuff, it states the two main culprits are the MAF or degraded O2 sensors. And since we've already replaced the O2s and MAF and the new MAF ohms good and after finding that evidence of a PCM retuned, maybe the PCM was originally tuned for use of the n2o, and they took some fuel out of the maps to compensate for the n2o kit adding fuel, assuming the n2o kit was a Wet kit... but this is all just speculation, i no way of actually knowing what was really done and tracking down the guy that did all his isn't going to happen, because he sold the car to my friend back in 2003. And the whole time my friend had it, the only problem had was clutch related. The CEL problem was a recent development over the past year or two.

Well, at this point we'll just have to wait to see how the PCM retune goes.

 

[aaron97]

Okay, the appointment to re-flash the ECU is later this week. In the mean time we took care of a few things that needed some attention. Like drain/refill the rear end and change the pinion shaft seal, drain/refill the trany with Royal Purple, installed the SLP catted x-pipe and Speedcal.

While he had the exhaust apart he looked for leaks or evidence of leaks and there was none. Even now that the SLP exhaust in on, it didnt change anything with the CEL. Just gotta take it easy over speed-bumps now because the cats hang low (running Sportline springs). But it sounds a littler better now.:rockon:

IMRC's cleaned and rebuilt with new seals and bearings.

Intake cleaned and going back together.

The SLP catted x-pipe.

The IMRC's before cleaning but after Seafoam..

Installed a Catch Can to try and cut down on the oil getting into the intake. Going to install a second one as soon as I find another one to make a matched pair.