92 XJ Running Rich?

[XJScott]

Hey All! It's been a while since I have posted anything here so I hope this is in the right forum! My apologies if it's not.

Anyhow, I have a 92 XJ 4.0 HO 5 speed with 213000 miles that is running rich. Lotsa gas being wasted. Atleast thats my assumption. It passed utah emissions in march with pretty good numbers but lately, when I get on it like to pass a truck on the freeway, I get black puffs out the back.
Also, when it's warmed up, it's dam hard to start. When I am driving it and have to stop at a light or stop sign, it gives me a hesitation when I first touch the gas pedal. Still has lotsa power when it does run smooth.

After it's warm and I do finally get it started, It runs REALLY rough and I look like a diesel engine going down the road till the fuel gets burnt out.

Pulled the plugs this weekend and they are black and sooty as well. They are not the grey/ash color they need to be. Also, the tail pipe is black and sooty and it is even starting to build up on my trailer hitch receiver.

The hard starting I thought was a CPS, but with the fuel consumption I am getting and the black soot, I am wondering that it's something else.

Any thoughts guy and gals? It's my daily driver and I am on kind of a tight budget.

Thanks!

 

[Silly Willy]

I would imagine the O2 Sensor should be able to help with this, That/they could be going bad Try putting a bottle of HEAT in the tank. could also try Sea Foam, and change the oil.

Just a few thoughts.

 

[DaveB]

I would look at the O2 and temp sensors. I have also seen cracked exhaust manifolds cause a rich condition because too much exhaust leaks out before the O2 sensor. Cracks on the manifolds are very common on these jeeps.

 

[XJScott]

Haven't tried HEAT and haven't done my yearly Seafoam/Call the fire dept thing yet.
O2 sensor was changed at emissions/inspection along with new plugs... I will try the HEAT today and see what happens.

 

[Tan Comanche]

The very first thing I would do is check all the vacuum lines. Replace if it is even questionable. Then check fuel pressure at the rail, pull the injectors and soak overnight in Seafoam. Double check all you electrical connectors. Clean the throttle body and the Idle control sensor. If you have a meter ohm out the throttle positioning sensor. Good luck.

 

[XJScott]

OK... played with it this morning, found a couple electrical connections pretty dirty. Soaked everything, Still hard to start when hot. When she is cold, she fires right up! Double checked everything, hoses, lines, etc...
Then..... I saw a resistor/ballast thing on the drivers side fender. 2 green wires. I noticed those connectors were pretty hashed up. I replaced the connectors and guess what! It fires up after about 2-3 cranks! everytime! What is it? I tried to follow the wires but they get lost in the wire harness.
Did I get lucky and find the problem?

Thanks for everyones help! The ol girl turned 220,000 miles today and is still runnin!

 

[DaveB]

It is a resistor that drops the voltage down a bit for the fuel pump. Maybe yours was dropping it a bit too much.

 

[XJScott]

Thanks Dave!
That does explain it.
Seems like after I cleaned the connectors, It has run better since!
Even coming off a stoplight , it doesn't hesitate anymore!

Thanks for everyones help! now for the trackbar and she will be ready for Moab again! (my wife has never been and she is jonesing to go!)