My post got no good replies originally so here goes again Im looking for some one who can read the signs of whats going on here. The truck has 78000 miles and is very clean. Not a oil leak anywhere ... About 1 yr ago the check engine light would come on intermidantly. Sometimes up a grade sometimes on a straight run. Then2 month would go by uneventful. Now its everyday. I took it in about 7 months ago and they said "UH I DUNNO MAYBE ITS YUR O2 Sensor ur Maybe you need a new exhaust system" .... So i left and havent done anything other than tune ups. Here is the senerio
Start up good but has slight rough idle more like a miss. Goes about 10 minutes then check engine light comes on BUT before that light comes on I can Predict it because i feel a drop in power slightly before. And if that lights on and im running a hill i have to get into the gas and i mean floor it. Now at times when the light is on i will get a surge of power THEN IT GOES OFF then i feel the drop and it come on and can stay on for entire trip. Now the gas milage if i remember when i got it 4 years ago was around 16-18. Now it is 7-9 and that is on the highway guys. ITS KILLIN ME. CODES !!!I did the code check and of course i got the lean on both sides and both o2 not switching ect. Alot of people are telling me to rip out the exhaust an go with a straight pipe to small muffler but i dunno what size or if dropping the cats is bad or how the heck i deal with the O2(they are all the way up on the headers 2 of em) So if this has been done before i would love some advise. But the signs im telling should ignite someone to know whats going on. Need some help here guys im in a situation where i have to work away from home and driving 600 miles a week at 7 miles a gallon on the highway is killing us HELP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

How about taking it to a good garage that has the handheld temp scanners (as well as diagnostic computers) to allow them to see exhaust restrictions, if it really has any? O2 sensors can generally be electrically checked once pulled out of a vehicle and heated up.

If your temp sensor was telling it the engine was cold the whole time, it could be sending more fuel to the engine (but I don't think it would be that much...).

WIth a fuel loss like that, I would guess it could be a restricted exhaust or a bad fuel pressure regulator?

It does seem like a lot of I-6 owners on this board change out a lot of sensors (or parts) with little to no results for their initial problem(s). With that in mind it might be worth paying for a real diagnostic check instead of getting suggestions from shops that haven't done tests on it.

I realize you probably want to do the work yourself, but you're going to need a few tools, and the proper readings, to start testing things.

WIth the OBD-II you probably have it should be a little easier for a computer to diagnose the problem.

But please keep us updated. I'd like to know what you find out.

 

Well, good advice above. If it were mine I would do this, in this order. Start the truck and let it warm up. Put a gloved hand over the tailpipe. If you can't hold it there without the exhaust kicking your hand away, then you probably don't have an exhaust restriction/problem. Now visit your trusty muffler shop and have them check your catalytic convertor...this should be free. If that checks out okay, I would suspect the fuel pressure regulator. I paid about $15 to have mine checked when it went bad, or you can buy a gauge and check it yourself. A chiltons or Haynes manual will tell you the right running pressure, or you can search the forum here to get that reading. If your fuel pressure regulator checks out okay, I would clear all the codes from the truck...unplug both battery cables for about 30 minutes then reconnect. Now drive the truck and see if the problem reoccurs. If it does, get your codes read or do it yourself with a scanner. Now work through the codes you get to isolate and solve the problem. You're obviously getting gas and burnin' a lot of it...so I'm leaning toward the fuel pressure regulator. That's what happened on my truck when the FPR went and it started drinking gas like a fish goes through water. Hope this helps.

 

[updated:LAST EDITED ON 22-Feb-02 AT 02:29 PM (EST)]If it is eating a lot of gas, and the codes show that the ECM thinks it is running lean? I would say the O2 sensors are toast.
Replace both O2 sensors and go from there.

Roger Lane

 

No good answers ???? I asked you what the code numbers were you got & you didnt reply except to say you posted them .... I didnt see any DTCode numbers , Phillip offered good you advice , Again no reply , then you say you didnt get any good advice . We can help you , But we need specific info . There are a few different things that can be the cause of the O2 Senosr Codes .

 

Hey, back to the O2 sensors. In a recent post somebody told me there were 4 or so (see https://www.ford-trucks.com/dcforum/DCForumID39/2728.html). No one said otherwise when I questioned this fact...now we are back to one or two. I can only find 1 on my 95 F-150. So what is it? I say one.

 

A 95 4.9L will only have one O2 Sensor .

 

Negative there are 2 O2 sensors on mine. Read the post!! Front and rear.... One on front exhaust header one on rear exhaust header. Each one is located near the top of the headers. I have yet to find more then 2.... Now replacing them would be all good im sure but i think the exhaust system itself has caused the sensors to fail due to a caddie blockage. My problem is how do i deal with the fact that the exhaust has two headers going into a y caddie out as one pipe there after. can i cut after the caddie and bust the insides out of the caddie and then go pipe back to small muffler?? HAS THIS BEEN DONE??? has anyone just gotten rid of the caddies period?? And if so how did you deal with the O2 sensors? Is there a aftermarket product to screw the o2 sensors into to give the a false positve reading? Is there a way to control what the o2 sensors are reporting to the BRAIN box?? I want my milage back. I found a blue box under my dash im assuming this is the computer. Funny i unplugged it and the trucks still runs....

 

Ok I might be ignnorant here but i thought that if the cat was pluged you would be getting a too rich code. I am haveing a check eng. light on my 460 and when I ran the codes I got 171 and 174 I believe it was. both sides too lean anyway. but the truck runs great. I cleared the codes and the light came back on about a week later but I haven't check to see if it is the same one's or not. I have to find someone with a tester again.