4.0l running rich

[fishfighter]

Got a big problem and it is getting out of hand.

My 1999 xj is sucking down gas big time. It's got to the point that I can see the fuel gauge going down as I drive. Really. The exhaust pipe on start up every morning just dumps carbon out big time.

I did chance plugs with no change. Now and then, I see and hear the engine jump in RPM's by a couple hundred.

Today, I will go by a Auto Zone to see if I can get them to pull any codes.

Mean time, if anyone has a idea as to what is what, I would be very thankful.

 

[brielly]

First, stop driving it for now. All that extra gas and carbon will harm your engine. Get the codes! My guess would be 02 sensor.

 

[Tim_MN]

O2 sensors and perhaps a cracked exhaust manifold. Cracked manifolds are very common.

.

 

[fishfighter]

Got codes and look all around. Didn't find a leak.

two codes

PO171, Fuel system lean bank #1. Got this to go with that.
171 indicates that bank ! system is to lean for a predetermined period of time.

Code 2

PO455, Major leak in purge control system.

I checked all vacuum lines and found nothing wrong with them.

Now what?

Thanks for any input.

 

[md21722]

Did you check the vacuum lines that go along the drivers side frame rail? There is a rubber junction that cracks and causes evap codes.

When you removed the plugs were all them the same?

If the O2 sensor is "lazy" or "dead" it will usually read lean and the engine dumps in more fuel to compensate. Other causes could be a manifold leak (intake/exhaust at the head). If you replace the O2 sensors, NTK brand is what you want.

 

[puntforloss]

Also, check injector gaskets and reset CPU.

 

[fishfighter]

It started raining yesterday and I couldn't get under to check the vacuum line going to the tank. Raining again this morning, but I have it under the carport and I will inspect that line today.

A little history. About two years ago I had to change out the fuel pump. I have only 136K miles. I bought it back in 2007 with 114K. I also changed the O2 probes about 3 years ago with NTK brand. Back then, the engine light came on, but didn't say which one was bad. That was the reason for changing both. IDK how to test them. Will read up on that.

When I changed the spark plugs, they were wet. I did go back with Autolite plugs.

I don't put much mileage on it. Use is around town and off roading a lot on the farm. Was cheaper lifting it then buying a new 4 wheeler. And yes, I go where ever I want with it no matter were. LOL

 

[fishfighter]

OK, got under and check the vacuum line all the way back. Looks like no problem there. Going to test the O2 probes and also clear the throttle body. I also picked up a can of spray carb cleaner. I will spray around all vacuum lines with the engine running to see if there is a race up if there is a leak.

 

[ehall]

Could be a number of things but I would start with the problems you know about. Fuel system lean error could explain it--if the O2 sensor is telling the computer that the exhaust is lean the computer will increase the fuel mix to compensate--you should replace the O2 if you don't know when they were last changed, after that start looking at what could cause the lean condition.

Major evap leak could also explain it. The evap system captures gasoline vapors from the top of the tank and runs it through a charcoal filter, then a solenoid will periodically dump the fuel into the intake. You could have a tear in the line or some other problem and dumping gas on the ground (I had that with my Cadillac).

Another thing is check your engine coolant temperature. When the car first starts the computer tries to help it warm up by running rich (extra gas in the exhaust to warm up the catalytic converter), and the computer uses the coolant sensor to determine when the engine is warmed up enough.

 

[old_man]

I vote for the O2 sensor.

 

[fishfighter]

OK, sprayed all vacuum lines, no change.

per the write up of testing the O2 probes, with the key on, I should have 12-14 volts feeding one of the wires to the sensor. I'm only getting 1.7V on the front and 1.5V on the rear. Now what?

 

[gradon]

O2 Heater mini fuse(15a?)in the pdc.


Sent from my iPhone using Tapatalk

 

[fishfighter]

O2 Heater mini fuse(15a?)in the pdc.


Sent from my iPhone using Tapatalk

Yep, 15A and good.

When and pick up a new front O2 probe. The old one had more then 1/8" carbon built on it. Also pulled the throttle body and clean that up. Had some carbon build up below the butterfly.

Now I need to read up on how to reset the computer. I'm sure it needs it.

 

[Djfbnfxjlife]

Oil pressure

im having an oil pressure sensor issue any suggestions?

 

[gradon]

(Nada)

 

[fishfighter]

Well, she up to par, like a champ. Thanks all. Had to be the O2 probe.