CEL problem please help - Ranger-Forums - The Ultimate Ford Ranger Resource


2.9L & 3.0L V6 Tech General discussion of 2.9L and 3.0L V6 Ford Ranger engines.

Reply
 
LinkBack Thread Tools Search this Thread
  #1  
Old 10-07-2015
Member
Thread Starter
 
Join Date: Jun 2015
Location: Modesto Ca
Posts: 15
Icon2 CEL problem please help

am getting po171 and po174 codes
this is what I have done
1 replaced upper and lower intake gaskets
2 replaced all vac hoses
3 replaced TB
4 replaced IAC
4 replaced ccv elbow




Now my question is will o2 sensor cause this if so any ideas on which one there are 4 1-at each ex. manifold 1 before cat and 1 after cat
Any and all ideas are appreciated throw them my way very frustrated
thank you in advance
Reply With Quote
  #2  
Old 10-07-2015
RF Veteran
iTrader: (1)
 
Join Date: Jan 2014
Location: Vancouver, BC
Posts: 7,582
No on the O2's, it would mean both O2 sensors on each exhaust manifold would have to fail at the same time, so very very unlikely.

171 and 174 means the computer is opening the fuel injectors on each bank longer than it should have to based on the air volume figure from MAF(mass air flow) sensor.
In other words if the computers calculation was used it would be a "Lean" mix, so computer ignores its calculation and opens injectors longer until the O2 sensors confirm a "normal" burn.

So engine never runs Lean, the codes are just giving driver a heads up that the calculations are wrong.
That could be because of a vacuum leak, but it would have to be from an upper intake manifold leak to effect Both Banks.
It could also be from low fuel pressure, computer can't check fuel pressure, it bases its calculations on factory preset pressure, 1998 Ranger 3.0l should have 65psi pressure at rail.

MAF sensor is where it all starts, these need to be cleaned every 5 years or so depending on driving conditions.
Computer reads the MAF data and bases how much fuel should be added to the available air to get 14:1 air:fuel ratio
Computer opens each fuel injector for specific length of time to add the calculated amount of fuel to the available air
Air:fuel is then burned in the cylinder
O2 sensors can only detect Oxygen in the exhaust, not fuel, if there is not enough oxygen then engine is running Rich and computer reduces the open time of injectors.
If there is too much oxygen then it was a Lean burn so computer opens injectors longer.
This is an instantaneous change in injector open time, so engine never runs rich or lean.
If the open time for the injectors fall outside the preset window for a 3.0l engine with 65psi fuel pressure then computer will set a Lean or Rich code.

The rear O2 sensors are to determine if cat converter is working, they are also used for long term fuel trims, but wouldn't be involved with 171/174 codes.

Last edited by RonD; 10-07-2015 at 06:02 PM.
Reply With Quote
  #3  
Old 10-08-2015
Member
Thread Starter
 
Join Date: Jun 2015
Location: Modesto Ca
Posts: 15
just had fuel rail pressure checked it is 45 to 50lbs could this be causing po171 and po174 codes if so then first check is fuel filter replacement am I correct
Reply With Quote
  #4  
Old 10-09-2015
RF Veteran
iTrader: (1)
 
Join Date: Jan 2014
Location: Vancouver, BC
Posts: 7,582
You should change filter every 5 years or so, and it could cause lower pressure but not likely without other symptoms, i.e. loss of power at highway speeds.

There are 2 fuel pressure specifications for 1998 3.0l Ranger
56-72psi
47-63psi
Not sure why this is?

Your 45-50psi shouldn't cause Lean codes with either, but pressure may drop more when engine is under load and that would cause Lean codes
Reply With Quote
Reply

Related Topics
Thread Thread Starter Forum Replies Last Post
CEL Bank 1 and 2 lean p0171 p0174 HELP PLEASE bryanjints 4.0L OHV & SOHC V6 Tech 21 12-19-2009 12:39 PM
Need help with 1996 2.3L CEL problem USMCWHITENER SOHC - 2.3L & 2.5L Lima Engines 5 08-18-2009 11:32 PM
New owner, problem CEL already Lighting Guy SOHC - 2.3L & 2.5L Lima Engines 6 04-17-2006 10:36 AM
CEL distress.. Help please! NHBubba_Revisited 4.0L OHV & SOHC V6 Tech 42 05-04-2005 01:19 PM


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not 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 Off
Refbacks are Off



All times are GMT -6. The time now is 01:31 AM.


We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.