i recently bought a 97 150 4x4 screw. has the 4.6 auto. I got the thing dirt cheap from a guy that just hates fords. to date she runs super, even on the coldest days she fires right up. Question check engine is on, ive not run any tests. the fella i got it from said he had testing done and showed 02 sensor bad. with the purchase he sent all the parts along he had bought and never installed. Im thinking of just changing out all 4 while im doing it, the truck has 178k on it. so the others are probably not far behind. does it make sense to just drop the exhaust pipes and do the change out on the shop floor, cause i looked at her from underneath and it looks darn near impossibe to get to the sensors from under the truck. anyone ever done it this way? was it better? thanks all

 

A couple of things to get you straight on first.
You need the code/s first to accuratly run with the issue.
Never trust another's position when they are not supplying any concrete info.
At the mileage the truck has, it won't hurt to change out the front sensors good or bad.
But without the codes you don't really know what your dealing with because codes do not tell you what parts to change.
Codes only tell you what operating system is seeing the trouble not what is causing it.
The linkage between the cause and how it sets a code can be quite far apart.

 

You don't have to drop the exhaust to change the sensors. Pull the front wheels and inner fenders, plenty of room. Use penetrating oil and a 22mm wrench.
Trying to break exhaust open that old would be way more work.

 

If its not throwing a rear O2 code, I would leave the rears alone. All those do is make sure the cats are working.

 

You are exactly right without codes its a guessing game! Good News!! I had to go into Auto Zone today to get some power steering fluid, and i thought hey i got the truck right here and they were kind enough to run the codes for me.. as follows

P0401 ECM has detected to little flow on the EGR system.
possible blocked passage on egr system
failed egr valve
egr solenoid faulty

P1131 detected bank 1 02 at its lean limit
probable cause: misfire on bank 1
vacuum leak affecting bank 1 only
fuel injector problem bank 1
engine mechanical condition

P1151 Lack of 02 switches bank 2 sensor 1
ECM could not adjust fuel trim because of a lean or rich condition.
fuel pressure high or low
maf sensor dirty/defective
vacuum leak on engine
leaking fuel injector or fuel pressure regulator

thats what i know as of today, the truck seems to run fine and if i unhook the battery for few secs then the engine light goes out. but comes back on after 50 or so miles. the idle runs really low after warm up about 400 rpm, hasnt stalled yet but it seems to want to. i cant really say if i got a miss or not, not that i can notice but on a v8 you know...
let me know what you guys think. should i just dive in on the egr and clean the ports out good. maybe thats whats throwing the other 2 codes?? thanks all

 

The idle doing that could very well be a vacuum leak. I am deleting the EGR on mine but won't have it done with a tune for a while yet. I had the 401 code off and on for a year.

 

Your O2 codes are not caused by EGR issues. You may have an EGR problem as well, but it is not the cause of your O2 sensor issues. I am an HHO distributor and have had to learn a lot about O2 sensors since they affect how the ECU controls the fuel injection system (we're talking gassers here, diesels don't have this issue) and therefore MUST be 'dealt with' in order to achieve maximum benefits from using HHO.

A couple things to know about O2 sensors. First, their useful lifespan is about 80k miles more or less, after that they tend to get S L O W like an old person using a walker. O2 sensors (when functioning properly) oscillate between "high" (usually 1V) and "low" (usually 0.1V) voltage levels twice per second, producing a nice smooth sine wave on an oscilloscope, usually from about 0.3V to about 0.8V or a range like that, depending on sensor, vehicle, etc. Also, BTW, two identical model vehicles (say 2003 F150 2dr, 2wd, 4.6 auto, long bed, etc - identical) may have DIFFERENT O2 sensors from different manufacturers, the maker (Ford) just uses what they have in stock - they are both correct and made for that application but may have slightly different parameters, but the ECU is matched to them so they work correctly. So if you buy new ones make sure they match. Anyway, as they age, they tend to slow down the oscillations. I've seen as much as 5 seconds between oscillations, which produced a 'stuck low' or stuck high' code depending on the sensor. This is what is happening with your "P1151 Lack of 02 switches bank 2 sensor 1" error code.

Second, when the ECU sees this signal low or high for so long it proclaims the sensor as bad and ignores it, resorting to 'safe' fuel mapping to try to protect overheating from a PERCEIVED lean burn condition and therefore dumping more fuel than it should. Your fuel mileage is probably suffering and replacing them should net you an increase as the ECU will accept the good readings and provide appropriate more efficient fuel mapping as designed.

A previous poster commented that the rear sensor's purpose are to validate the catalytic converter function and he is right, but if those go bad your ECU will still go to 'safe' mode. If your truck has 178k AND original O2 sensors they should be replaced, anything over 80k on an O2 sensor is pushing its expected lifespan. After you replace them if you still get a lean error code then I would look into the suggested causes, but usually if you have a misfire you will get a code that will tell you WHICH CYLINDER, which it didn't. I would replace the O2 sensors first and if the error codes specify "sensor 1" then they are the fronts, you could just replace those but if you need to replace the rears too it may be a PITA to open everything up again - I don't know that is up to you.

 

ok what i did this weekend was to remove the throttle body completely and cleaned thoroughly. both egr ports were completely plugged tight. the backside of the throttle plate was black with carbon so i just cleaned the whole nine yards while i had it all apart. one problem i got it the lower nut on the egr tube is shot, its still on the manifold but 1/2 the nut is split out at the top so i was able to remove it, and i can sorta slide the flared end back in and then tighten the upper nut guess i will need to get a junkyard riser pipe. I reset the computer and took her into town to get gas, seems alot smoother and it doesnt idle down hard like it did. in gear it idles about 600 rpm now. but the check engine light came back on. i guess its the 02 sensors. will do that on different day cant get that truck in my shop and theres snow on the ground outside. lol