Yep...check engine light trouble on my 98 with 147k.

I pulled the codes and I get a 172 and 175 which I understand translates to my oxygen sensors signaling that the truck sucking fuel like crazy and not enough air.

There is literally black carbon being spit out of the exhaust like nuts, but I knew that because its sucking down gas like there is no tomorrow. If I am lucky I get 100 miles per TANK!

In terms of performance, the idle is rough on start up. It idles iratically and once I get going, it loses power. I literally floor it on inclines, but lose a lot of speed. I also have a nasty kick when changing gears.

So, I cleaned the MAF with MAF cleaner (it looked okay), I cleaned the IAC, I cleaned the PCV, I checked all the hoses and they look pretty good and I don't see signs of a vacuum leak (I tried spraying carb cleaner and listening to the idle to change). Air filter looks good. Then I replaced all the plugs and wires. I also replaced the EGR sensor. I finally replaced once of the two 02 sensors, the one under the passenger seat right before the cat. The other two look pretty good. I keep clearing the error after each repair I make to no avail. Also, no fuel out of the hose to the fuel pressure reg. No cracks in fuel line.

Truck runs better than before because i cleaned everything and new plugs, but still the same problems. It's a matter of time before carbon builds up again.

I am at a loss. Any advice before I go out and replace any more parts?

 

lol...if i had money, I'd have a mechanic do all the work.

 

Replace your O2 sensors.

The codes should tell you what bank the bad ones are on.

 

I'm thinking 02 as well

 

so I should replace the other 2 oxygen sensors even though I'm still getting the same signal from the 02 sensor I replaced? The one under the drivers side (bank 2) triggers the one under the passenger seat?

 

edit... reading comprehension>me

sounds like a bad cat to be honest.

Seafoam it and call me in the morning.

 

Symptoms

You will more than likely not notice any drivability problems, although there may be symptoms such as a misfire.

Causes

A code P0172 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters can cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
There could be a vacuum leak.
There could be a fuel pressure or delivery problem
Possible Solutions

Possible solutions include:

Inspect all vacuum and PCV hoses, replace if necessary
Cleanthe MAF sensor. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect fuel lines for cracks, leaks, or pinches
Check the fuel pressure at the fuel rail
Check the fuel injectors, they may be dirty. Use fuel injector cleaner or get them professionally cleaned/replaced.
Check for an exhaust leak before the first oxygen sensor (this is unlikely to cause the problem, but it is possible)

 

Probably wouldn't hurt.

O2 sensors are a maintenance item that a lot of people forget about. From what I've been told, they should be replaced every 60K.

Let us know if that's not the issue.

 

i had the same problem but my front drive shaft was rubbing the wire and finally burned through it causing that so i replaced all three sensors and cleaned my MAF and no more problems. and this XeRo dude needs to be banned or something.

 

x2

While you're at it you may as well replace them all to be sure, no use having one go 5k later and have to get dirty all over again.

If that's not the fix I am thinking a MAFS or intake sensors/timing but o2 sensor would be the first solution to try.

 

Now that I think about it more, I am going to go with MAF.

My truck was running horrible prior to me replacing my MAF. Replaced it, and it ran fine. Got better gas mileage too.

Should be able to get one for under $100 with yours as a core deposit.

 

screw that, go to autozone they sell an aerosol of electric parts cleaner. Dries in seconds. I doubt it's a bad maf but a faulty reading maf. Also would rule that out and for $7 better to do first than spend $100.

 

The easy way to test a bad MAF is with the vehicle running unplug the MAF, if it starts running worse then thats usualy not the problem. If it runs the sam unplugged then that would usualy be the problem.

 

Electronics cleaner is a temporary fix. She'll have to replace the MAF sooner then later anyway, if it is faulty.

If the code is saying it is running a low or high voltage, check the actual cables going into the MAF. Could have a bad ground wire.

Not true. My MAF was BAD, and unplugging it did make the truck run worse. It works on some vehicles to do it that way, not on all.

She already cleaned it with electronics cleaner, and said it ran a little better. So, I could be wrong.

But, my guess is either the other O2's are bad (you said you have two left, which means about $105 to replace them, if I remember correctly), or your MAF, or the connectors.

 

i've got a spare maf, and if your talking bout the exhaust and carbon build up, that sounds like a clogged muffler.

 

Hmm sounds like there is alot to check.. I would also recommend throttle body cleaner since it cleans that areas as well as the Intake Manifold and removes garbage in that area as well. I would also get those 02's checked since its throwing a code to you.

 

Quote:Also, no fuel out of the hose to the fuel pressure reg.

I take it this fuel system uses a fuel return line to the tank.
I would have to say a faulty fuel regulator is keeping the pressure too high to the injectors.
Check the fuel pressure at the fuel rail.I think you'll find it is too high.

 

can you test your fuel pressure? what about the fuel filter?

you checked for all vacuum leaks?

 

I thoroughly cleaned the MAF and checked the connector. I will take it off and see if it it runs the same. Better to try first than blow a 100 bucks on a MAF right away.

I didn't check the pressure in the fuel rail because I don't have the proper fitting for the pressure gauge. The only reason I don't think its a faulty FPR is because I didn't see any fuel in the hose while truck was running. If it was at fault, wouldn't there be fuel in the hose?

I checked the fuel line and there aren't any cracks or bends or signs of wear. The only reason I don't think its the fuel filter is if there was a clog, wouldn't it run LEAN?

Maybe I should break down and take it in and have a shop run a more through scan to see if the remaining 02 sensors are at fault rather than blowing yet another 120 bucks on 2 more 02 sensors and another 100 bucks on a MAF. The o2 in the cat, looks brand new, connector looks okay, as for the one under the drivers side, it looks pretty darned new too.

I will seafoam it too. I don't think its just a clogged cat because I don't see how that would have such a tremendous affect on my loss in power, misfiring and erratic idle. I think it is becoming clogged because there's too much fuel and not enough air to result in proper combustion.

 

so no vacuum leaks? when i have seen that code on fords in the past its normally some type of vacuum leak.

 

As for Vacuum leaks.

I checked, I made my friends check and I made my father check...I don't see any leaks. I did the whole carb cleaner test too! Maybe I'm missing something?

I ran my fingers over every hose.

 

my gas mileage dropped down to 12 mpg when i was all stock when my maf took a **** i got a new one from a junk yard and i was right back up to 19 to 20 mpg

 

Did you have any other symptoms? Did the idle jump up and down and would it rattle when you floor it like it was misfiring?

 

i'm thinking maybe i should check my coil pack too...i'm not throwing a misfire code though.

 

Since both banks are running lean then it is most likely not an 02 sensor problem. vacuum leaks will cause it to run lean not rich.

I'd check for leaky fuel injectors. Make sure the fuel system holds pressure.