Got back from a trip to san diego... drove 1200 miles total.... truck was awesome, it performed well. love the power the 5.0 has driving on the hilly california freeways. anyway, on the drive back to here (arizona), the CEL came on about 140 miles away from home.... stopped to get gas and checked everything (oil, tranny oil, coolant, all other fluids, checked for smoke, belt was ok, and smelled exhaust for anything funky), all was ok. no abnormal noises either. shut the truck off a few times during the rest of the day as we did some shopping and went out for food, all separate trips. CEL stayed on.... on the last trip home for the night it went off while driving and hasnt been on since... this was this last wednesday and its now friday and still hasnt come on. i will get the code read if it is still stored on tuesday. any ideas beforehand? i'm thinking a sensor somewhere that got too hot, like an o2 sensor or the cats...

97 X 5.0 AWD; 90,000 miles

 

over the course of the last 20k miles on my 97 (190k+ now) the sensors on the catalytic converters have gone... in most cases it started as you said, intermittent CEL for a while and then on all the time.

 

Scan the code, get us the number, then come back here if you need help deciphering said code.

We can't tell you what to look for. That's what scanning for codes is all about.

You will have a code stored in the computer, despite what a normal autozoner will tell you.

 

i had a blazer and every time i drove it into the mountains the cel would come on got it checked out and it was the air in the mountains was thinner and the computer could not adjust the fuel curve enough for the thinner air

 

got 'er read today and P1131 came up twice. he said one was stored and one was actual. dont know what that means since the CEL wasnt on, should have been just 1 stored. anyway, the reader said "fuel air metering". any ideas? thanks fellas.

the CEL came on at about sea level, or maybe 100 feet above. but i had just got done driving 4000+ feet mountains for 90-100 miles. dont know if its worth anything. it hasnt come on since then (this last wednesday)

 

i've read that an o2 sensor could be bad or the MAF could be dirty/contaminated....

 

DTC P1131 indicates the system is correcting RICH for an overly LEAN condition. The Heated Oxygen Sensor (HO2S) voltage is less than 0.45 volts. This is usually due to a vacuum leak after the MAF. It can also be caused by a bad PCV valve or PCV system hose.

It can also be caused by low fuel pressure or a plugged injector.

However, since you have just completed a quick altitude change, I would reset the code and see if it comes back.... My2c

 

there is no vacuum leak anywhere in the intake system, my bet is the pcv system. its so rusty back there... i havent checked it out yet since i've owned the truck, but just about everything else in there is rusted through and through.

 

If you want to bring it by tomorrow, Sunday, I'm free in the morning. Down at Gilbert and Ocotillo. I'll PM you my phone number. I can scan your truck and look at real time data, all the O2's and we can clean your MAF sensor to see if that helps.

 

i have to work all day tomorrow, my weekends are tuesday and wednesday..... tuesday would be the first day i could come by. let me know if either works for you. thanks a ton for the offer

 

Tuesday night is OK. 5:30 or so? Give me a call.

 

OK so we scanned it and got 2 different 1131 codes. Book says bank 1 sensor 1, that's front right side sensor. Ran real time test and got OK switch both banks sensor 1, no switching running lean bank 1 sensor 2 and very slow switching bank 2 sensor 2.

This 5.0 has a goofy exhaust. It is a dual exhaust all the way back until the muffler where its a 2 into one out muffler. There are either 4 cats or 2 cats and a resonators...if those are even still used. I found the bank 2 rear O2 in between the cat and other thing, cat or resonator. I couldn't see any of the other 3 sensors...which have to be there or the scanner wouldn't have shown them.

We cleared the codes with the scanner, ran it again and nothing. CEL has not come on in some time. But by the previous codes and the scanner readings, something is still not right.

I'm puzzled as to why there was a front sensor stored code but bothe rear sensors showed bad performance. I don't even understand why there are 2 rear sensors either unless they are somehow supposed to indicate cat performance. The cats don't affect O2 levels...but then again I hated chemistry so who knows what reaction goes on inside the cat.

Maybe Mrshorty can help.

So it's not prudent to go throwing components at a problem to see if symptoms just go away. If someone can explain what we saw and know it's a bad right rear O2 and the left rear looks lazy so change it too, then lets hear the advice.

Otherwise, I would do some more investigation...when was the last tune up? What do the plugs look like right now? Recheck the vacuum lines and intkae (though that looked pretty clean to me). Are there any obvious things, low hanging fruit?

Other thing too is that exhaust looked pretty darn rusted. Anyone know the effect of a rusted out Cat?

Could be the sensors are OK and telling you a real situation that is being caused by some other bad component(s).

 

yea. what jeff said. the exhaust should be stock, dont know if the previous owner messed with it, didnt seem like the type. hasnt had a tuneup since i've owned it (last october) and i havent checked the plugs. they look like a s.o.a.b. to get at.....

i really dont think there is a vaccum leak anywhere with the intake... i've taken it apart and put it back together an umpteenth amount of times... and the joints seem to be in great condition

no other obvious problems, truck performs like a champ. the only other thing is low mpg. and i'm assuming a bad (2) o2 sensor can cause this as well....
the exhaust sounds great, no leaks that i can hear and no funny noises.

the CEL hasnt come back on...

anyone else have any ideas?

 

Indeed, the 5.0L has four catalytic converters... when I get home today I can see if the shop manual has anything about diagnosing the sensors (as well as the locations) around them.

 

all OBDII compliant cars/trucks 96-NEWER have O2 sensors before and after the cats. The rear sensors basically detect cat performance. If you hollow out a cat the rear sensor picks that up right away. If you are positive there are no vaccuum leaks after the MAF and none at the intake the problem sounds like a lazy O2 sensor. Probably a good idea to change Bank 1 sensor 1 and bank 2 sensor 1. Rear O2 sensors probably ok