P0171?!?! Need help plz
#1
CF Veteran
Thread Starter
Join Date: May 2009
Location: Columbus, Ohio
Posts: 1,471
Likes: 0
Received 1 Like
on
1 Post
Year: 1996
Model: Cherokee
Engine: 4.0L
P0171?!?! Need help plz
So I have the P0171 System to Lean MIL. I checked my 02 sensors replaced the downstream.I have a small Crack in my headers.I get about 6 miles per gallon and pour black smoke on the high revs.Can't figure out whats the problem.It runs fine until about 45 then it starts to knock and surge.but 0-35 mph it feels fine.Any Advice??
#2
Senior Member
Join Date: May 2008
Location: Michigan
Posts: 814
Likes: 0
Received 7 Likes
on
7 Posts
Year: 1996
Model: Cherokee
Engine: 4.0
Small crack in the exhaust is letting air into the system that is tricking the O2 into thinking the engin is running lean. The computer sees this and reacts by dumping fuel to compensate. I would fix the exhaust and replace both Up and Down stream 02 sensors to start.
#5
Senior Member
Join Date: May 2008
Location: Michigan
Posts: 814
Likes: 0
Received 7 Likes
on
7 Posts
Year: 1996
Model: Cherokee
Engine: 4.0
Im 100% sure on my opinion, without seeing the vehicle and doing diag over the interweb from what you have typed, Im still about an 80%. Is the exhaust only cracked in that spot or is it cracked some place else you can't see? The computer reads the up and down stream o2 sensor outputs and compares them, if the computer sees that the engin is running lean it is going to add fuel, causing black smoke and poor fuel mileage
Thread
Thread Starter
Forum
Replies
Last Post
nasonguy
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
3
01-11-2011 09:09 AM
mattsmako
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go here
0
05-25-2010 06:34 PM
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)