if the o2 sensor is bad, tomarrow im going to put a belt tensioner on it and take out my o2 sensor and see if it's bad. the o2 sensor will be burnt black if its back right??

 

its more from the fault in the air flow throug the cat that causes the engine light to come on.

 

I'd just kill the damn cat. We can get away with that here.

 

had no idea it monitored the air flow in the cats...new one on me....

 

the rattling noise and the check engine light may or may not be related. i agree he should check the codes...if the O2 sensors are after the cats and the cats are bad that could cause MIL to come on. cheers, garsten

 

yall keep saying plug it in. my 94 doesnt have a spot to plug in anything does it?? i went to advance auto parts one time going to do that and they said a 94 doesnt have that?

 

You're 94 should have a diagnostic connector under the hood. Left (drivers side) fenderwell. Should have a red plastic cover for the plug.
Bob

 

Actually, on a 94 the computer doesn't monitor catalyst efficency at all, that is strictly and OBD-II function.

However, many things that kill cats will cause a check engine light, such as an o2 sensor constantly reading lean which makes the computer spray more fuel that the engine doesn't need, and the cat gets overheated and destroyed because of the excessively rich mixture it has to burn off.

pretty much any failure that makes the computer go rich or the engine misfire badly will kill a cat, and since running rich and misfiring are emissions concerns, they will typically light the MIL lamp

 

ok heres what happen. i took my o2 sensor out and it was black, we wiped it off and it was white. I put it back in and didnt think nothing else about it. Well i had this ball under my hood that was a vaccum resovoir for the heater. I looked at daddy's 94 and his didnt have it on there so i took it off and hooked it up like he had his. I went to leave his house and for some reason the b**** dont have any power. When im driving down the road the power just goes away. But when i press the gas to the floor it'll pick back up and take off .I took it to auto zone and the code came back with my tps(throttle position sensor) So bought that freaking 35 dollar piece of rubber with 3 wires!! Put it on went down the road and its still doing the same thing. But could the o2 make my truck run like this? When i went to walmart last night, i saw this program thats called auto tech. I opened the flap on it and it was showing a 90 taurus. On the problems it had "lacks power on flat road and up hills). Then it said that the problem was a stopped up cat. I'm, seriously thinking about going and gettin that software could be the best 10 bux i ever spent. Btw: its for 600 different makes and models of cars ranging from 83-2006 i believe.

 

I own a 95 F150 5.0 efi. For weeks on end I chased down the rattle while accelerating mainly up the mountain side.. My problem was caused by a plugged cat.. easy way to determine if your cat is bad is take your truck to muff shop and have them test pressure before and after cat. Takes about ten mins total. Requires a hole be drilled and gage placed on hole while engine is running any reading over 4 psi is good under 3psi equals plugged cat. ideal reading is around 7 psi..

also note your timing both with the spout connector connected and without the spout hooked up. reason for the connector contected is to get a baseline of how much the computer is compensating..if you need to make adjustments to timing make sure the spout is not hooked up..

my truck has 207000 miles and its still going...strong

 

how bout checking the temperature of the cat with an infared thermometer?

temp should be at least 100 deg. hotter after the cat.



Jack01,

you are talking about a standard backpressure measurement, and anything over 3 psi is not good, with 7 psi being an excessively restricted exhaust. Also, they should be able to test backpressure before the cat without drilling a hole by removing the o2 sensor.

 

i cant believe your still on this. go to www.fordfuelinjection.com. there are instuctions on setting up your tps to operate properly. you cant just throw it on. also hook back up what ever you changed to look like your dads setup. for what ever reason yours is different.
if you simply unhook your Y pipe from the manifolds and drive it down the street, its going to be louder then hell but you will notice an improvement right away. this would tell ya if the cat is bad or not.

also have you checked your timeing as well? it should be at 10* btdc with spout connector removed. also what spark plugs are you running and how old are the plug wires? also check your fuel pressure at the rail. and pull the codes yourself using the paper clip method, do both KOEO and KOER tests that website above shows how.

 

ok...i guess the sensor fixed itself. i have had it on for a week and the check engine light hasnt came on. i called the muffler place and they said it sounds like the cat....whenever i can get over there i'll have it checked. as for right now. its running pretty good.

 

remember just because there is no cel doesnt mean there isnt a problem. a

 

i understand. it doesnt pick up everything. I asked the dude at the muffler place if her could cut it and he said that if he gets caught its a $2500 fine. But i want to know if the o2 sensor is in front of the cat how will it effect me in the long run?? (thats what he said)