CEL OBDII P0171 - Bad Gas! - JeepForum.com

LinkBack Thread Tools
post #1 of 4 Old 06-26-2013, 09:08 AM Thread Starter
4xTroy's Avatar
2002 WJ 
Join Date: May 2013
Location: Pulaski
Posts: 472
CEL OBDII P0171 - Bad Gas!

Not even Jeep specific, but I wanted to share for posterity and search engines.

Last weekend, my 2002 WJ 4.7L started running a little rough and the CEL came on. Checking the code, I had a P0171, indicating the system was running lean. At the same time, I had some black soot blowing out the tail pipe.

Google came up with many suggested troubleshooting steps covering the vacuum, intake, exhaust, o2 sensors, etc..., I was prepared to start what troubleshooting I could without a garage, but then I remembered that I had bad gas before, and this might be the cause of this issue as well.

So when I got down to half a tank, I put a can of sea foam and filled up with 93 from another station. I took her out on the Interstate for some quality WOT time. I pulled off the next exit, and sure enough, the code cleared itself. I ran a few more exits for some more WOT to be sure, and we're back to normal.

Last edited by 4xTroy; 09-01-2013 at 08:37 PM.
4xTroy is online now  
Sponsored Links
post #2 of 4 Old 09-01-2013, 08:36 PM Thread Starter
4xTroy's Avatar
2002 WJ 
Join Date: May 2013
Location: Pulaski
Posts: 472
Ok, it's been like a month now. The P0171 came back, along with a P0139 for the O2 sensor. I've been unable to find any vacuum leaks and fuel efficiency wasn't suffering. I cleared the codes, but they came back.

The other day, I took it in to get the guys at a friend's shop to fix the wiring in the drivers door, and asked them to look for vacuum leaks as well. They couldn't find any either, which made me feel better, but they did suggest that it might be an issue with the IAC Valve. So, today I took it out and cleaned it with some TBC.

Jeep wouldn't start. Huh? Oh yeah, plug the IAC back in.

Try again, it starts but immediately stalls. Start again, give it some gas, it runs fine at ~1000rpm. Let it go, and it dies. After a few more starts, it finally idles, but a bit rough, and I get a new code, P0505 (IAC System Malfunction). Grrr... a few more starts and a couple runs around the block, the code clears. Start and it idles fine. Run at 2000RPM for 20-30 seconds, then it dies when I let off the throttle.

A few hours later, it seems to be better, but I'm not 100% sure I can trust it. Any ideas on this? Would it help to hose the idle intake with TBC while the engine is running?

I know its recommended to stick with Mopar for sensors and such, but what are the after market controllers (BWD/Delphi/Wells) from Advance any good? Getting to a Mopar dealer is a PITA.


4xTroy is online now  
post #3 of 4 Old 09-02-2013, 10:01 AM
Brian & Stewy in 2016!
GilaMtnJeep's Avatar
2003 TJ Wrangler 
Join Date: Aug 2008
Location: Silver City
Posts: 4,265
Just my 2 and humble opinion here.

Don't get the stuff from advance/autozone/etc. If you're gonna buy aftermarket get a good brand. The Echelin brand from NAPA is good quality. I've used them for years and have never had an issue with anything I put on my heep.

Silence is Golden, Duct tape comes in Many Colors.

Journeyman Meterman IBEW Local 611

Work with enthusiasm as though you were working for the Lord rather than for man.


Siena Jeep Owner's Member 25

/l ,[____],
l---L -0lllllll0-

()_) ()_)-O-)_)
GilaMtnJeep is offline  
post #4 of 4 Old 09-02-2013, 09:04 PM Thread Starter
4xTroy's Avatar
2002 WJ 
Join Date: May 2013
Location: Pulaski
Posts: 472
Unfortunately, Napa is only slightly more convenient as Mopar, but I'll keep that in mind.

I think I need to learn more patience. The P0505 cleared and the ECU has apparently re-learned how to use the IAC after it's cleaning.

Guess I need to sleep on these things before posting.


4xTroy is online now  

Quick Reply

Register Now

In order to be able to post messages on the JeepForum.com forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.

User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.


Confirm Password:
Email Address
Please enter a valid e-mail address for yourself.

Email Address:


Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.

Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page

Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are On
Refbacks are On

For the best viewing experience please update your browser to Google Chrome