Help with code P0171

[venams03]

I just installed a new JLT Carbon Fiber Big Air CAI kit (127mm) on my '08 GT500 and loaded a new tune from Lund that was supposed to match my mods (only other mod is a 1.5" Stainless Works Offroad X (no cats) and 3" catback (very open exhaust).

I had a previous Lund tune loaded just for the exhaust prior to adding the JLT CAI andit really improved the throttle response.

Now after adding the CAI and the new tune, it just doesn't seem to be as punchy which is odd. I also can't hear the supercharger whine unless I abolutely floor it in second gear, and then it's only heard for a short time and very faint. This is disappointing since the main reason for adding the CAI was to get back the supercharger noise.

Anyway on my third trip out the "check engine" light comes on. My XCAL=3 says it's P0171. Googled and posts say that the engine is running lean? That is scary to me right? It's bad to run lean on a supercharged engine right?

Any suggestions on what to do? I'm afraid to drive it now and Lethal (where I bought CAI) and JLT are closed on the weekend so I can't goto them for help right now

 

[GNasty]

P0171 is a lean condition. More than likely since this happened after the CAI I would guess you have a vacuum leak somewhere. Double check your work to make sure all clamps are tight, hoses are installed, and that the mass air flow sensor is seated properly.

 

[spitin venom]

There is unmetered air getting in to your engine. Check after the MAF.

 

[venams03]

I checked the MAF connection, EGR and vacuum hose and all appear to be OK. The only other connection after the MAF is the rubber boot connection at the Throttle body. Maybe I should take the tube off and reconnect all over again?

 

[GNasty]

I would definitely check it. I have seen the rubber get folded under the throttle body when installing it.

 

[Van@RevanRacing]

I checked the MAF connection, EGR and vacuum hose and all appear to be OK. The only other connection after the MAF is the rubber boot connection at the Throttle body. Maybe I should take the tube off and reconnect all over again?

Yes.

You need to go through it thoroughly. Make sure all of the clamps are snug and tight and that all of the connections are good. P0171 is unmetered air after the MAF causing a lean condition.

If you installed an oil separator at the same time make sure the drain isn't open and make sure all oil separators are good and tight and have proper connection in the PCV system.

 

[venams03]

Cleared the DTC code first.

Then I took everything off and used thinner to clean the areas that will seat with the rubber. Reinstalled everything once again and made sure all connections/areas are snug. Reattached MAF connection, EGR and vacuum line and made sure those were tight as well.

Took it out for a spin and seemed OK but I noticed once again that the RPMs were staying rather high once the clutch pedal was depressed. It takes longer for the RPM to drop than when it was stock or with the previous tune. When stopped at a light it kind of abruplty stumbles at 1100rpm before dipping to about 600rpm before leveling off at 800rpm. This is new and I don't know why that is happening?

Also topped off the tank with "fresh" 93 octane since the residual was in the tank over the winter.

Same results. I don't feel a "seat of the pants" difference and I have to absolutely nail it in 2nd gear to see 7-8 pounds of boost and I can barely hear the supercharger whine for just a bit before the exhaust drowns it out.

Not sure what to think at this point?

 

[GNasty]

These symptoms really sound like a vacuum leak. If you have a propane tank, attatch a small hose to the end of it. Open the propane bottle and hold the hose around the areas that you have worked on. The propane will enter the airflow and change the fuel mixture therefore changing the idle speed. When the idle speed changes, you have found the location of the vacuum leak. I didn't see it in your list, you didn't change the throttle body did you?

 

[venams03]

I didn't change or do anything to the throttlebody. There is a barb and rubber nipple on the right side that I was told was a vacuum line but I inspected it and didn't find any problems?

 

[walked_u_hard]

You have a bad O2 sensor or you have an exhaust leak. If your car was actually running lean you would have both 171 and a 174 codes(lean both banks). Easy way to test this is to swap the front O2 sensors from side to side, if the code follows then you have a bad O2, if not u have a exhaust leak.

This happened on my Cobra and drove me nuts trying to track it down!

 

[99cobraUgotbit]

You have a bad O2 sensor or you have an exhaust leak. If your car was actually running lean you would have both 171 and a 174 codes(lean both banks). Easy way to test this is to swap the front O2 sensors from side to side, if the code follows then you have a bad O2, if not u have a exhaust leak.

This happened on my Cobra and drove me nuts trying to track it down!

+1......02's could be the issue. Switch them out and see what happens

 

[jamied]

I also have an 08, when I went from the stock air box to an open element I needed to adjust the MAF transfer curve. It's a different intake so the transfer curve will be off. The flow of the closed air box of the 2007-09 vs the 2010-2013 is different. Ford will have the data from a flow bench. For a JLT you will have to start from scratch. Jon can revise your tune. Jamie

 

[venams03]

You have a bad O2 sensor or you have an exhaust leak. If your car was actually running lean you would have both 171 and a 174 codes(lean both banks). Easy way to test this is to swap the front O2 sensors from side to side, if the code follows then you have a bad O2, if not u have a exhaust leak.

This happened on my Cobra and drove me nuts trying to track it down!

But wouldn't I have gotten the code prior to installing the new intake/tune if I had a bad 02 or leak?

I emailed Jon Lund II and he told me clear code and see if it comes back. So far no code but I told him that I also have hanging RPMs. If I run through the gears, when I depress the clutch pedal (netrual) and off gas the RPMs used to drop to idle around 800RPM. With the new intake and tune it stays kind of high and takes a long time to drop. Makes downshifting/engine braking kind of hard. When I approach a light and push the clutch in it hangs around 1100RPM and then makes an abrupt "Burp" and drops to about 500RPM before leveling off finally at 800RPM?

 

[stkjock]

when you loaded the tune - did you allow the car to relearn the idle?

 

[venams03]

when you loaded the tune - did you allow the car to relearn the idle?

Sorry for my ignorance. How is that done exactly. I believe that I started the car and waited for about 2 minutes before I took her for a spin.

 

[APMECH]

But wouldn't I have gotten the code prior to installing the new intake/tune if I had a bad 02 or leak?

I emailed Jon Lund II and he told me clear code and see if it comes back. So far no code but I told him that I also have hanging RPMs. If I run through the gears, when I depress the clutch pedal (netrual) and off gas the RPMs used to drop to idle around 800RPM. With the new intake and tune it stays kind of high and takes a long time to drop. Makes downshifting/engine braking kind of hard. When I approach a light and push the clutch in it hangs around 1100RPM and then makes an abrupt "Burp" and drops to about 500RPM before leveling off finally at 800RPM?

If you verified everything is connected properly, and it ran great just before this, I would definitely suspect the tune. (you changed 2 things right? cai and tune?) Any local dyno shops in the area that can tune it?

 

[stkjock]

Sorry for my ignorance. How is that done exactly. I believe that I started the car and waited for about 2 minutes before I took her for a spin.

load tune
start car
idle for 4-5 mins a/c off
turn on a/c
idle 4-5 mins

 

[venams03]

load tune
start car
idle for 4-5 mins a/c off
turn on a/c
idle 4-5 mins

Thanks STK.

Lund emailed me a new tune to try. I guess there actually was a parameter that held the RPMs higher during shifts.

Going to download and reflash the car and see what happens. Hopefully that will take care of the RPMs issue and the P0171 code.

APMECH, Yes that was the only 2 things I changed: intake and tune so I was leaning towards the tune as well

 

[stkjock]

He probably adjusted the dashpot setting - after you load the tune do the relearn.

 

[walked_u_hard]

But wouldn't I have gotten the code prior to installing the new intake/tune if I had a bad 02 or leak?

Its possible, things go bad when they go bad.

If its not a bad O2 then yes it would most likely be the dashpot decay settings that are causing this. If you dont add at least 10% these cars wont decel properly, and rpms wont want to drop between shifts.

dashpot decay will change how fast your RPM's drop after the accelerator is released. You can think of it this way, dashpot will change how fast the throttle blade closes and by how much. Its rare to be left out, but this time of year tuners are absolutely slammed with people wanting tunes since people are starting to drive their fun cars again, so some small things could be over looked.