Bronco Forum - Full Size Ford Bronco Forum banner

1 - 17 of 17 Posts

·
Registered
Joined
·
16 Posts
Discussion Starter #1
I have a 96 that is giving a "lean fuel on bank 1" (or something like that) code. Since the truck has over 100K miles, I wanted to check the O2 sensors. The Haynes book talks about the O2 sensor mounted in the exhaust pipe near the starter. But PartsGeek showed a rear sensor (the one I described, I suppose) and a front sensor. Question is where is this front sensor. I one mounted in each header somewhere?
 

·
Wrenching for a Livin'
Joined
·
6,950 Posts
sounds like you have a p0171 system lean bank 1. usually its NOT an o2 sensor problem, although it is a possibility.

Normally this is caused by a vaccum leak. checked for cracked plastic lines and make sure your pcv valve is functioning properly.

Also could be the mass air starting to get flakey, but about as likely as an o2 sensor.

On that truck there should be a sensor by each manifold and one after the cat.
 

·
Registered
Joined
·
222 Posts
1st thing I would do would be to clean the maf. I had this same code and cleaning the maf fixed problem. Autozone has cans of maf cleaner pretty cheap.
 

·
Registered
Joined
·
473 Posts
mine through that code it was the mass air flow sensor. the oil from the k&n filter got to it. be careful if you have a k&n filter. expensive part to change
 

·
Wrenching for a Livin'
Joined
·
6,950 Posts
mine through that code it was the mass air flow sensor. the oil from the k&n filter got to it. be careful if you have a k&n filter. expensive part to change
Yes, i forgot about this...ford had a tsb on it for that code and p0174 as well. Clean the maf with some electronic cleaner replace your air filter with a STOCK one, and go from there. if it comes back you may need a maf sensor.

Make sure you have no vaccum leaks thou.
 

·
Cleaning the trails
Joined
·
931 Posts
There are three. One on each Y pipe before the first cat and after it (if I remember right). Get a scantool to see which code it is throwing. Is the check engine (CEL light) on?

The MAF cleaner is the red can of CRC electronics parts cleaner. Autozone has it.. If you get near the 57/60, I can scan it for you after work
 

·
Super Moderator
Joined
·
25,802 Posts
yo, a Mag advised which is great info!
by HardMaple ; "...On a V8 engine, O2 #11 is near the engine on same side as #1 cylinder, #21 is near the engine on opposite side. On ALL single exhaust systems #12 is near the catalytic converters (behind them on California emissions, between them on all others), #22 does not exist. With dual exhaust #12 is around the cat on the #1 cylinder side, #22 is on the other side near the cat.

P0135 = HO2S HTR-11
P0141 = HO2S HTR-12
P0155 = HO2S HTR-21
P0161 = HO2S HTR-22

If you end up replacing the sensor, don't bother buying the Ford Factory socket. I used an open-end wrench (metric 20 or 22mm I think) because a socket wouldn't fit up there. The only real trick is trying to put the new one in because the wiring harness on the Bosch sensor is very long and when you are trying to thread the sensor back in, the wiring will try to spin it back out. But you may not have too much trouble since yours is in the rear position..."
----

the tsb w/DTCs;
DRIVEABILITY - HO2S (HEATED OXYGEN SENSOR), CATALYST, AND FUEL SYSTEM MONITORS - SERVICE TIPS - OBD II VEHICLES ONLY - 96 Bronco, TSB 01-9-7
Source: by Ford via v8sho.com @ http://www.v8sho.com/SHO/TSB0197HO2SServiceTips.htm
 

·
Registered
Joined
·
411 Posts
I too had same issue and it turned out to be a dirty MAF.

Even after I sprayed it with MAF cleaner it would still get p0171 & p0174 codes.

I had to actually rub the crud off (very gently with q-tips and ethyl alcohol) of the thermistors. I used a magnifying glass to inspect and make sure the thermistor wires were squeaky clean - after that no more codes and my bronco stopped pinging at WOT as well.
 

·
Registered
Joined
·
4 Posts
Replacement of the o2 sensors is 20-25 minute job. The two up front are easy but the rear one is a pain... located on top of the exhaust pipe. Tight fit but doable. Good luck
 

·
Registered
Joined
·
222 Posts
maf or vacuum leaks. the 02s are telling you what the problem is, not that they are the problem. Think to yourself, "what is causing a lean condition?" unmetered air and or the wrong amount or air is being measured. This leads to a vacuum leak, dirty maf, low FP, ETC. very very outside chance that it is the 02s.

P0171 - System to Lean (Bank 1) The Adaptive Fuel Strategy continuously monitors fuel delivery hardware. The test fails when the adaptive fuel tables reach a rich calibrated limit. For lean and rich DTCs:
Fuel system
Excessive fuel pressure.
Leaking/contaminated fuel injectors.
Leaking fuel pressure regulator.
Low fuel pressure or running out of fuel.
Vapor recovery system.
Induction system:
Air leaks after the MAF.
Vacuum Leaks.
PCV system.
Improperly seated engine oil dipstick.
EGR system:
Leaking gasket.
Stuck EGR valve.
Leaking diaphragm or EVR.
Base Engine:
Oil overfill.
Cam timing.
Cylinder compression.
Exhaust leaks before or near the HO2Ss.
 

·
Registered
Joined
·
16 Posts
Discussion Starter #11
Thanks to all. I replaced all the hardline vacuum hoses, replaced the air filter, and cleaned the MAF. Result: cleared the codes and none returned. Appreciate all the help. BTW: bought the OBDII scan software from OBDCOM ( http://www.obdcom.com/ ). It is hosted by a laptop & comes with the connector. Great detail and easy to use.
 

·
Registered
Joined
·
1 Posts
Hey I'm having the same problem I cleaned my maf and throttle body which hoses should i check for a vacum leak and how do i check for that
 

·
Banned
Joined
·
19,980 Posts
Check ALL the vacuum lines & exhuast at idle using a stethoscope without its probe (open hose). Click these & read the captions:

. .
 

·
Registered
Joined
·
78 Posts
My 96 was running pretty damn rough and I just attributed it to the 261,500 miles that it now has on it. When it got really bad I started looking around for an easy reason. Turns out that after I replaced all of the vacuum lines, the EGR solonid and PCV valve she runs like a top!!! Once again, the KISS principle was the correct way to go.
 

·
Super Moderator
Joined
·
25,802 Posts
yo Rickmastick & Richard729
Vacuum Leak Test; see my Post #11 at http://fullsizebronco.com/forum/showthread.php?t=206824&highlight=Vacuum+Leak+Test;+idling

note that many overlook HVAC systems vacuum circuits for doors & associated vac motors, dedicated vac tank (in additition to Emission Vac Tank);
"...The air handling system is designed to provide defrost when no vacuum is applied to any of the three air door vacuum motors. This is done to prevent a situation where defrost cannot be obtained due to a system vacuum leak. Instead, a leak in the vacuum control circuit will send all airflow to the defroster outlets. This condition may occur during acceleration (slow leak), may exist at all times (large leak) and may happen only when certain specific functions are selected, indicating a leak in that portion of the circuit. ..." by Ford



PCV valve/ grommet;intake manifold gasket & throttle body (Worn throttle shaft) and lower intake; & vac tree

Read More
Normal Engine Vacuum at Idle is 15-22 in-Hg for 96 Bronco
 

·
Registered
Joined
·
1 Posts
yo miesk5 thanks for the reply most help ive goten with my truck in giving me a clue on what the heck is going on. I have both right bank and left bank lean codes so im guessing exhaust manifold when i go to give it full throttle it shakes and kinda stutters also leaks quite a bit of oil ... dont know if that has anything to do with it. im gong to start the trouble shooting with some carb cleaner and check the lines and proceed from there thanks man and will thank you in advance for anymore advice and for the advice already given.
 

·
Super Moderator
Joined
·
25,802 Posts
yo RIXK, YW, a quixk test for any vac leaks in HVAC system is; "...In 92-96, The air handling system is designed to provide defrost when no vacuum is applied to any of the three air door vacuum motors. This is done to prevent a situation where defrost cannot be obtained due to a system vacuum leak. Instead, a leak in the vacuum control circuit will send all airflow to the defroster outlets. This condition may occur during acceleration (slow leak), may exist at all times (large leak) and may happen only when certain specific functions are selected, indicating a leak in that portion of the circuit. ..."
 
1 - 17 of 17 Posts
Top