1995 f350 460 speed density E4oD
Have a check engine light its code 173 with the o2 not switching and the system being rich. I have replaced the o2 with a brand new bosch. Still a light. Took it to the shop and they checked all the stuff, fuel pressure ok, MAP readings ok, ECT-ok, IAR-ok, they said that the "cat converter is broke and incorrect"- replaced the cat with a piece of straight pipe and it was not clogged when I took it out. Have reset the computer by unhooking the batter numerous times. The light comes on about 15 minutes after I start driving and it will go away every time I turn it off and then about 15 minutes into driving it, it will come back on. Last time I checked the codes when the light came on it also showed a 126 that the MAP sensor was out of range. Have not noticed a loss of power since this has started happening and it does not smell any richer than it has before sooooo...
ANY IDEAS???

 

get some brake clean and shoot it around the intake an vacuum lines. Mine just did this and was getting 6mpg and I found that the egr valve was loose sucking air so it was dumping fuel trying to compensate If I sprayed it it would shut the motor down but it ran fine other wise. so look for a vacuum leak

 

Since the "shop" you took it to was full of bad advice I would not trust any of their test results. Re-check the fuel pressure, you can rent a tester at most auto part stores.

Code 126, if valid, is probably the root cause of your rich Code 173. You can test it with a DVM that has the function to measure frequency. You can use the same DVM to test the other sensors.

For reference: OldFuelInjection

 

I bought 15 feet if vacum line and replaced every single one if those silly lines so definentally not vac leak...also code 126 is what i got AFTER i took it to the shop before that it wad jist the 173...also rechecked fuel pressure and its a solid 30 all the way through the rpms......so time for a new map sensor?

 

The fuel pressure should rise to ~40 PSI under full throttle/heavy load conditions.

Do not forget there are vacuum reservoirs that can leak too. Replacing just the lines will not cure that.

 

Well this light is still driving me crazy...i ended up replacing the map sensor and that didnt help. Also used up a full can of brake cleaner spraying all over and looking for vacum leaks which there was none and i unplugged the vacum line that goes from the map sensor to the intake manifold and then the motor died is this normal?

 

Black tape will fix that light...

 

In my experience, yes that is quite normal.

Another reason why I do not like the spray method to find vacuum leaks. I use a small handheld vacuum pump gauge to test each vacuum circuit.

I am still concerned with your statement about the fuel pressure.

 

Well im kinda thinking the regulator becasuse both fuel tanks both do the same thing but if the regulator was bad and i had low fuel pressure it would be lean not rich correct?

 

You are correct, but you may have more than one issue. Since the fuel pressure test results are not correct, work on what you know is not in specification.

 

So i went and started it up and let it idle in the driveway for half an hour no light ...then i went to drive it and about a mile up the road the light came on. The truck still pulls strong as ever but there is a small miss when i start it up the idle bounces from 600-800 rpm and goes away after it warms up and no i dont want to just tape over the light...too easy

 

Just trying to get as mich information out there as possible for you guys to help me, i redid the exhaust manifolds a while back. One of them has a gasket on it and the other one i took and had it milled down. But it still has a hair of a leak on the side with the gasket. Do you guys think that could be casuing this, maybe air coming in through there and hitting the 02 and then making it run richer?

 

Even if you got it milled, you should have used a gasket. It depends on how bad the leak is but it probably isn't the cause.

Going back to rla... You should re-check your fuel pressure... while under load going down the road.

 

Sounds like you have bad fuel pressure and the leak in your exhaust is also allowing ambient air (via a Venturi effect) to mix with hot exhaust. The ambient air brings higher oxygen content raising the overall exhaust gas oxygen content proportionally to the size of the leak----the oxygen sensor will react accordingly and send erroneous feedback to the computer throwing mix off.

Other results include incomplete NOX reductions which can affect your emissions test, carbon build up and reduced fuel economy.

With that leak your exhaust velocity is also dropping keeping the exhaust valves in constant contact with hot exhaust gases -- those exhaust valves won't cool entirely through contact with the cylinder head and will eventually burn up........

 

Hey i think i might have it. The egr tube thing (passenger side...blows out air) that thing if i remember used to stop blowing at times before this started happening and now it blows out air constantly and dosent shut. I dont know if this is the egr valve or what its a can like object with a bunch of tubes coming off of it and it blows out air....?