94 XLT runs rich

[p100ki]

I have a 94 XLT four door automatic Explorer and it was owned by a little old lady before i got it a couple months ago, i've only driven it a couple weeks. It is really clean and i got it cheap since it has 160,000 miles on it. The problem is the fact it runs rich, i searched here and cleaned the MAFS and the IAC along with the normal seafoaming. That cleaned the idle up great but it is still blowing carbon out of the exhaust. If i rev it up in park in my driveway there will be a black mark on the ground from the exhaust.

The check engine light has never come on and it drives totally fine. After the seafoam it quit bogging down when you laid it on the floor and will easily spin the tires in drive from a stop instead of hesitating. It however is still running rich and with no check engine light i'm not sure what to replace. I'm thinking about replacing the O2 sensor if another round of seafoam doesn't do it.

I know the little old lady that had it just drove it around town and probably only got it to freeway speeds maybe once a month, maybe.

 

[Darrman]

You may want to invest in a code scanner, I got mine for $35 at the local parts store. It should be able to tell you anything thats not working right.
It does sound like the o2 senser, but seeing they are $50 apiece and your truck has 3-4, I would get the scanner first.
Some parts stores offer a free computer scanning, like the battery and alternater testing.

 

[MrShorty]

Check for gas in the vacuum line to the fuel pressure regulator and check fuel pressure.

 

[mrboyle]

x2 on the fuel pressure regulator!

 

[p100ki]

x2 on the fuel pressure regulator!

Where will i find the regulator? I've never worked on a 4.0 so all this is pretty new to me. I'm used to the V10 in my truck.

 

[BrooklynBay]

The regulator has the fuel rail Schraeder valve. I suspect that it could be the ECT (engine coolant temperature sensor). Use the following chart to troubleshoot it:

 

[MrShorty]

Where will i find the regulator? I've never worked on a 4.0 so all this is pretty new to me. I'm used to the V10 in my truck.

FPR is on the front end of the fuel rail, passenger side, with a fuel line coming off the top.

 

[p100ki]

FPR is on the front end of the fuel rail, passenger side, with a fuel line coming off the top.

Thanks, i'll probably get a chance to look at it tomorrow

 

[TedJ]

Check for holes in the exhaust before the oxygen sensor...not all exhaust passes by the sensor so it reads lean and richens it up. (or bad sensor) Saw this happen on a Hyundai excel that came into the school auto shop. Beteween it running rich and blowing oil smoke it was like a james bond getaway car. Welded up the pipe and fixed the leak before the sensor, but the fist sized hole in the muffler was a bit big to fix lol. No muffler = more fun.

I would think that a bad pressure reg etc would set a code b/c the oxygen sensor would tell it its running waay to rich. Maybe not though. A scantool would be a good thing to view the sensor data.

Coolant temp sensor is a good idea too. Its not hard to check everything that has been mentioned so go for it. Autozone's loan a tool is your friend.

-Ted

 

[EMG7895]

Hows your gas mileage? I believe I am having the same problem, but cant quite pinpoint it. I am thinking its probably o2 sensors/cats.

 

[p100ki]

Hows your gas mileage? I believe I am having the same problem, but cant quite pinpoint it. I am thinking its probably o2 sensors/cats.

I'm not really sure because my wife filled the tank up and i don't know how much it holds. But i did get 275 miles before i had to fill it up again, it wasn't empty yet either.