Troublesome Trouble Codes... P0171

[COBRASVT]

My 171 code was caused by an exhaust leak....

 

[STAMPEDE3]

My 171 code was caused by an exhaust leak....

What I'm still thinking.

 

[aaron97]

Did your friend go back to the dealer about the PCM flash? If the car had nitros and possible a SC, it's probably still tuned for those things which would really screw up the tune since they are no longer installed.... With all the stuff you've changed, and since you haven't found any exhaust leaks (which is what I suspected to be the problem), I'm leaning toward a really bad tune or maybe even a faulty PCM. Have you checked the ground for the PCM?

Ya, he took it back to the dealer and had them do it again while he watched.

Going lean when you let off on the gas is normal. That part of it is nothing to worry about.

Any way your buddy can capture some logs for us to look at?

Problem is that it is going so lean the PCM has a hard time rebounding from the lean condition and fights to bring it back, which is when it trips the pending code.

What I'm still thinking.

I know, but he is 100% sure there is not a leak. Couple other things i didnt mention, remember before the 171 would always pop first and then the 174. We swapped the injectors around and that didnt change, but after all that other stuff and eventually we fixed it and she ran fine for about a week. Then the codes came back, but this time its the 174 that pops first followed by the 171. So i ordered a set of FMS 24lb injectors. But the codes came back as well as the high idle issues.
I talked to him yesterday and turns out, he forgot to do a full PCM reset. So he did that and so far he is still getting the pending codes but they are not tripping the light. He drove it for 3 drive cycles and still only has the pending codes. So maybe the PCM is starting to relearn the new injectors. He is going to get another real time read and see if that's the case. Hopefully it is and the pending codes will go away.

On another note, all this troubleshooting has still been a positive thing, because everything that was changed was bad. So when all is said and done, everything under the hood is new except the motor itself. And the dual oil catch cans are working like a champ. I will post pics in a few, i was impressed with how clean they are keeping the intake now.

 

[aaron97]

Some before and after catch can shots. The Before pic was taken after a Seafoam cleaning. The After pic is with about 1200 miles after cleaning of the intake.

Before:

After:

Where the catch cans are mounted.

 

[Tx_Diablous]

I found a service tip put out by ford if you like I can e-mail it to ya. Not sure it will help much but it is good reading. Let me know.

 

[aaron97]

I found a service tip put out by ford if you like I can e-mail it to ya. Not sure it will help much but it is good reading. Let me know.

Thanks, that's actually a good piece, but i had it already and followed everything it mentions as probably causes.

My buddy is going to mess with the car more this weekend and we'll see what happens with the pending codes. Thing i dont get is, the code is pending every drive cycle, but the books say the CEL should come on after the pending codes have been tripped for two consecutive cycles. I dont know, we'll see.

 

[aaron97]

After another PCM reset, he has driven several drive cycles now and not codes, not even Pending codes have come back yet. So looks like changing the fuel injectors helped after all.

 

[Tx_Diablous]

Check this out. It can take a while to set everything depening on how he is driving it.
http://www.obdii.com/drivecycleford.html

 

[aaron97]

Check this out. It can take a while to set everything depening on how he is driving it.
http://www.obdii.com/drivecycleford.html

Ya, he knows about all that and knows the drive cycle is complete when the P1000 goes away. Sometimes it takes a couple days, because like you said, depends on how he is driving it.

 

[mwolson]

I finally got some time to do some part throttle datalogging today to start fixing my lean bank codes. Thought you might be interested.

It is pretty obvious that my MAF transfer function is way off. I logged the MAF AD counts and the STFTs with adaptive turned off. My banks are about 3% apart, but I suspect most of that comes from using the NB simulator out of my PLX M300 WB on the driver's side, with a new Bosch sensor. However, the passenger side O2 sensor may be the original, so I am thinking of replacing it. So I averaged the two banks together to figure my correction factor for the time being.

Here is the data I got:

MAF_AD_COUNTS Bank Ave
177 0.996
179 0.995
237 1.210
246 1.136
275 1.079
303 1.184
314 1.175
355 1.196
365 1.207
385 1.190
392 1.207
395 1.174
404 1.166
407 1.217
435 1.166
454 1.125
503 1.126

You can see that it is pretty close to 1 at idle, but it goes out of wack fast. The regions where the STFTs are over 20% off, actually maxed out over 25% a lot, and I am sure that maxing out is what is causing my codes. I am too tired to fix the bottom end of the transfer function tonight, but I'l keep you informed as I progress if you are interested.

 

[aaron97]

Ever heard of high IAT's causing Lean conditions? We noticed the IAT is 138 degrees... and just for comparison (I know another cobra would have been better but..) we looked at the IAT's on his Audi A4 and it was only 102 degrees under the same conditions.

The codes came back, but they only come up at idle when the engine is at normal operating temps. I don't know what the air temp was that day, but 138 sounds too high and he said it takes a long time while driving to get the temps to start coming down.

Does anyone know what the normal IAT's should be? Like xx degrees above ambient air temps? That would be a good start. The stock air filter box and filter are from a '01 GT and the snorkel is removed, would that have anything to do with it?

 

[mwolson]

The codes will only get triggered when the car is running in closed loop because it happens when the learned fuel trims pass a pre-programmed threshold. The car runs in open loop for a couple of minutes (a bit longer when cold) on starting, and at WOT, for example. But during normal driving, it runs in closed loop, always learning the typical adjustment required from the O2 sensors. That is when your codes will usually be thrown.

The PCM compensates for IATs, so that should not be the root cause of the lean condition.

That said, the less hot air you can pull in from the engine compartment, the better your car will run. Pulling the snorkel could make it easier for hot engine compartment air to get in, but I never liked the stock air box with or without the snorkel. I prefer a system that has less room for hot air to come in. Unfortunately, the Volant CAI I use is no longer available for our cars.

 

[aaron97]

The codes will only get triggered when the car is running in closed loop because it happens when the learned fuel trims pass a pre-programmed threshold. The car runs in open loop for a couple of minutes (a bit longer when cold) on starting, and at WOT, for example. But during normal driving, it runs in closed loop, always learning the typical adjustment required from the O2 sensors. That is when your codes will usually be thrown.

The PCM compensates for IATs, so that should not be the root cause of the lean condition.

That said, the less hot air you can pull in from the engine compartment, the better your car will run. Pulling the snorkel could make it easier for hot engine compartment air to get in, but I never liked the stock air box with or without the snorkel. I prefer a system that has less room for hot air to come in. Unfortunately, the Volant CAI I use is no longer available for our cars.

Ya, i understand that, but when doing real time reads, you can tell the lean code condition is only at idle or sometime right when you tap the gas at idle, never while driving. Its a rarity now, but its still happen every now and then and throws the code.

I talked to him and the out side air temps that day were less than 80 degrees, so that's almost a 60 degree difference from what the ambient air temp and the intake air temp. Doesnt that seem like a huge difference? And with it being less than 80 degrees outside, wouldn't you think the IAT's would come down considerable when driving, its got to be getting hot air from somewhere or a faulty reading. I wonder if making my own CAI will help or moving the IAT sensor into the filter housing.

I'm just not having any luck.. its going on 2am where i am and my bathroom has started a waterfall from the ceiling. It was so loud it woke me up. What really sucks is i have to get up a 4am for work...:cuss:

 

[mwolson]

I have my IAT sensor after my non-intercooled blower so my IATs are typically between 100 and 150 degrees above ambient, sometimes as high as 200. Of course mine is throwing lean codes, too, but it wasn't before. And you saw my trims, so my problem is pretty obvious. I really don't think high IATs is it.

If you want to run an experiment, pull the IAT sensor out of it's grommet, plug the grommet and let the IAT sensor hang on the outside of the fender. You could even put a fan on the sensor to ensure it is staying cool. I wouldn't drive it that way, but you can see if it throws any codes that way.

Regarding your plumbing situation and your car situation, Eric Clapton said it best, "If it wasn't for bad luck, I wouldn't have no luck at all." Born under a bad sign.

Good luck.

 

[Tx_Diablous]

I have talked about shims on the o2's. I can see you do not want to try that....ok with me. You do not have stock pipes as I remember and I hear a lot of people without stock pipes have o2 problems. I am running Bass ANI-X catted (I hope I got that right I catch such shit when I use the wrong terms) with flowmasters and have never had an O2 code. Could it be that the pipes you are using just dont put the 02 close enought to the collecter? Your air temp does not throw an alarm with me but if you want, tell me where you took the temp and I will measure the temp with a temp probe where you took your temp. Mine is a mostly stock 98 with a 96 bottom end I put in 3 weeks ago.

 

[RoadZOmbie]

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.

That catch can how functional/effective is it as opposed to the smaller Glass/Plastic canisters?

 

[aaron97]

That catch can how functional/effective is it as opposed to the smaller Glass/Plastic canisters?

Its very effective, if you look at the before and after pictures, you'll see after the install, there is no oil wetting in the intake manifold at all. Those canisters came off eBay for about $20 each. One was blue so i had it repainted black to so they would match. As for your question, i dont know how much more effective they are over the smaller glass type.

 

[98 svt]

That looks like a big cluster **** though.
It may be effective, but it sure as hell doesn't look good.

I don't feel oour cars really NEED the catch can, but I'm sure it helps.
If I were to use one, I'd use a small setup.