Need some diagnostic expertise

[npearman]

Sorry this a little long, but I figured the more detail the better.
I have a 94X that has been giving me some problems on long road trips. I was driving back from Florida last week and the check engine light came on. The truck was also having a hard time keeping up with the cruise control set at 65mph (engine bogging). The only way I could accelerate at highway speeds was to floor it and let it drop down into a passing gear which caused black smoke to come shooting out of the exhaust. My gas mileage also went from a crappy 16mpg to an even crappier 10mpg. I went and bought a code scanner and got the following codes with the key on engine off scan:
33- EGR valve not opening;insufficient flow detected
172-Heated oxygen sensor indicates lean condition, right side
182-Adaptive fuel rich limit reached at idle, right side

I was getting ready to drive from Birmingham to Chicago the next day and didn't have time to screw with it myself, so I took it to a local mechanic (of course he had to do his own scan$$$)and he said it had a vaccum leak and replaced the vaccum hose to the EGR valve. I take off to Chicago and the truck is running fine till about 300 miles into the trip. Same exact symptoms. I finally get to Chicago after stopping for gas 5 times!!!!! and take it to a Ford dealer the next day. They run the diagnostics again$$$$ and drive it around a while and can't get the symptoms to reoccur. They said that the codes they got could mean a lot of different things and that if the problems are not occuring when they run the codes, they couldn't do much. I guess I could be thankful that they didn't just start replacing a bunch of stuff and hoped it fixed the problem. So i picked the truck up, drove it for about 50 miles and I can't get it to do anything. I pack up and head back to Birmingham today and the truck runs fine till 400 miles into the trip. Same exact thing happens again, black smoke, bogging, check engine, piss pour gas mileage, etc. As soon as I got home, before I even turned the truck off, I scanned it again.
This time I did the engine running scan and got the following:
136-Heated oxygen sensor indicates lean condition, left side
172-Heated oxygen sensor indicates lean condition, right side

I also did the key on engine off scan and got:
172-Heated oxygen sensor indicates lean condition, right side
176-Heated oxygen sensor indicates lean condition, left side
181-Adaptive fuel rich limit reached at part throttle, right side
542-fuel pump circuit open; PCM to motor

So after all this hassle and forking out cash for diagnostic fees and gas, is it just the damn O2 sensors?????? Any suggestions/advice would be appreciated as long as I don't have to pay you a diagnostic fee

Nate

 

[TDG]

Sounds like the Fuel Pressure Regulator took a dump on you. Do a search (for FPR) and you should find a ton of topics dealing with the little thing. On the other hand I have had a MAS do almost the same thing.

 

[npearman]

FPR

If it is the FPR, wouldn't the symptoms occur all the time and not just when the truck has been at highway speeds for several hundred miles? I also forgot to mentionin my post that the truck only has 60k miles on it. Thanks for the tip.
Nate

 

[sholzee]

Maybe a long shot but could the catalyic converters be plugging up at highway speed. I would not think it would come and go. Just a thought.

 

[TDG]

When the FPR on my 92 went out it was pretty random. Sometimes it would never come on sometimes it took a lot of driving to get it to come on and the rest of the time it would come on within 5 miles of driving. The FRP has also been known to cause all kinds of funny codes relating to the O2 sensors and the engine running at the lean/rich adaptive limit, poor fuel mileage, a nasty smell, smoke and a number of other things. I'm not sure if age is more of a factor than mileage, 60k on a 94 tells me that it hasn’t been driven too much, sometimes vehicles that aren’t driven enough will have more problems than those that are driven the long mile. But like I said I've had the MAS do some crazy stuff when I got water inside of it. Just something to look at.

 

[irtySanchez]

My gas mileage has been in the toilet lately also. I am taking a road trip Thursday and don't have 500 dollars to spend on gas.
I know the o2 sensors are originals, so I decided to go ahead and replace them anyways. Hopefully it can get me back up to 20 mpg on the freeway.

My suggestion is replace them. It is routine maintenance and can't do anything but help.

Good Luck!!!!!!!

 

[npearman]

FPR

I forgot to mention in my original post that the Ford dealer did check the fuel pressure when it was there and they said it was fine. Of course, like I said, the truck didn't have the symptoms when I took it in. I'm still leaning toward the O2 sensors, but I'm worried that it is something else that has fouled the sensors in the first place and replacing these will only be a temporary fix. BTW- how much to replace the FPR???? Thanks

Nate

 

[Fun94Sport]

npearman, I have a 94 sport with 98k miles with the EXACT same problem that your describing. I've had it into the dealership on several occasions and they have never been able to correct the problem. I'm going to go back through my old invoices and see if they replaced the O2 sensors, or the FPR.

If you find out it's something else, please post what it was here. I've had this problem for about 2 years now and have not been able to get it resolved.

PS - this message board is wonderful!!

 

[TDG]

Dealerships

I hate ford dealers, but I've already gone off enough about them in other threads. If I can fix it in my driveway as a shade tree mechanic I see no reason why they shouldn’t be able to get it right at least the 2nd time around, it seems to me that there should be at least one person in each dealership with enough memory to remember seeing a problem in the past and fixing it. Nuf said.

I've seen FPRs run anywhere from $60 something at AutoZone to over a $100 at carparts.com. I remember when I had this problem I was chasing my butt around in a circle (More so than normally) swapping O2s and messing with other stuff, it wasn’t till I found this forum (way back when it was the old style) that I even thought about the FPR. One of these days when I'm bored I think I'll put the old one back on and rig a fuel pressure gauge where I can see it while I'm driving and see just what happens when they crap out, cause mine tested just fine before and after I changed it. Since both O2s are reading about the same and returning the same faults I'm suggesting something a little more centralized, it would be very strange if both failed at the same time.

When you did the engine running scan was the system in open or closed loop status?

 

[npearman]

It was in close loop status

 

[jimbo74]

stupid ford dealers....

anyway i had same problem on way home from wheeling trip

i went to go visit my old auto shop teacher. we hooked it up to the code reader. it had stored codes of exhaust gas oxygen sensor lean and exhaust gas oxygen sensor rich.....

IT IS YOUR O2 SENSOR!!!

 

[leebo]

Reset that dang computer. When was the last time the computer was cleared of the codes?? With that many I'd guess at least a few of them are memory codes. Unhook the battery for awhile, the try the codes again.

I do think the 02's are gone though.

 

[npearman]

Thanks for input

I'll replace the O2's this weekend and clear the codes out of the computer. I'll report back to tell you how it went.

Nate

 

[oahrens]

Checklist

Sounds like your on the right track...

I had same problem on my 91....Here's what I did

Clean sensors (cheap)
replaced o2's
replaced MAF
replaced FPR
finally found it was the Cats.

Try to feel how strong the exhaust is at higher RPM's.

Keep updating

 

[npearman]

Problem Solved!!!!!!!!!!!!!!!!!!

I bought some new ac/delco o2 sensors ($50x2=$100) and went home to install them. I crawled under the truck and saw that it was going to be fairly easy to remove the sensors from the exhaust pipes but that I would need baby hands and some long @ss arms that were capable of bending in six different directions to reach the o2 connections up behind the bell housing. Maybe it's easier to reach these on the 2x2 models but there is a ton of stuff in the way on the 4x4's. I probably could have unconnected the connections from the top if layed on the engine, but I could only get one hand in there at a time. Reconnecting the new ones would have been really tough. After looking it over, it wasn't worth the $87 bucks the mechanic was going to charge me to install. I took it to him, he replaced and cleared out the codes and I drove the truck on a 300 mile trip. My mileage went from 10mpg to 17 mpg (all interstate and a/c running. I also cleaned the MAF, but it was the o2 sensors. No more check engine light either. The mechanic did say that just disconnecting the battery for 30 monutes does not clear out all the codes. You have to use some type of code scanner, to truly clear them all out?? Whatever, I am saving a ton in gas and no more black smoke. Thanks for the help you guys provided.

Nate

 

[white94]

This is probably a dumb question, but can someone tell me what an MAF and FPR are?

 

[sholzee]

MAF = Mass Air Flow sensor

MAF is mounted in the hose between the air cleaner and throttle body. It is close to the air cleaner and you will see the electrical connector going to it. It measures the amount of air coming into the motor.

FPR = Fuel Pressure Regulator

The fuel pump supplies more fuel then the motor needs the regulator maintains a constant pressure and excess fuel is sent back to the tank through a return line.

 

[npearman]

MAF stands for Mass Airflow Unit. Basically controls/regulates how much air gets into the engine for combustion purposes. FPR stand for fuel pressure regulator. I think this controls how much pressure there is in the fuel lines but I'm pretty sure it does more than that.