90 XJ shooting fire out of tail pipe....please help me...

I just got a 90 XJ and it ran like shit, I put new plugs, wires, cap, and rotor in. It runs smoother now, but the RPMS cary when it idles.... i checked for vacuum leaks and could not find any... Well the other night i started it up and i looked underneath cause i saw some light coming from underneath and there were flames shooting out of my exaust pipe... Now mind you i cut the exhaust off right after the cat, so it was shooting flames about a foot long underneath the jeep. this was after only about 45 seconds of it being on and idling. I would guess that it is running WAY too rich. Any ideas on what could cause the rpm to vary when idling and why it is sooo rich? PLEASE HELP ME.... I dont want my poor jeep to start on fire... any ideas are greatly appreciated.. Thanks

MonsterXJ97 said:

I just got a 90 XJ and it ran like shit, I put new plugs, wires, cap, and rotor in. It runs smoother now, but the RPMS cary when it idles.... i checked for vacuum leaks and could not find any... Well the other night i started it up and i looked underneath cause i saw some light coming from underneath and there were flames shooting out of my exaust pipe... Now mind you i cut the exhaust off right after the cat, so it was shooting flames about a foot long underneath the jeep. this was after only about 45 seconds of it being on and idling. I would guess that it is running WAY too rich. Any ideas on what could cause the rpm to vary when idling and why it is sooo rich? PLEASE HELP ME.... I dont want my poor jeep to start on fire... any ideas are greatly appreciated.. Thanks

Click to expand...

injector stuck in open position?

wow

usualy people pay a lot of moeny for that and do something like put a spark pulg at the end of the pipe...

check the injectors and you will most likely need to change the O2 sensor...

XJ_ranger said:

wow

usualy people pay a lot of moeny for that and do something like put a spark pulg at the end of the pipe...

Click to expand...

That's what went through my mind as I read it.
Why would you want to fix it?

What's the sensor that determines the air/fuel ratio? Isn't there a sensor that senses the ratio and then changes it, so the ratio is constantly changing but within certain parameters? I would think that might be bad and thus making it run too rich.

Hmm...a foot long flame after the cat...isn't that pretty close to the, umm, gas tank?

Yea....I would'nt fix it either!!

Get an elbo and a foot of pipe, point your exhaust out the side and go
burn the shins of people waiting at a bus stop!!

(could'nt resist)

^^^ i agree! haha. while this isnt entirely out of the question, I am sure most of our vehicles will shoot flames out if there are no mufflers.........its just a CAT. the mufflers can act as spark arrestors, to a point, and diminish any flame before it reaches the tailpipe at the end of the vehicle.

but since you have other symptoms as well, i would wager something else is up

have you checked the timing? sounds like its not firing porperly. you might check that and if you cant time it, try checking to see if the chain is ready to break. Take off the belt and rotor cap. Turn the crank left and right and see if you can turn it excessively either way before the chain turns the rotor.

Check the firing order and plug wires. I think its 153624 look on the intake manifold its stamped there.

since you have had it a short time I would do a couple of things.

1. Clean the throttle body and pay close attention to the AIS and its by pass circuit.
2. Check the TPS voltage settings
3. Check the EGR operation.
4. Another way to check for vacuum leaks is to use brake cleaner to spray around the intake manifold where it meets the head. Leaks can occurr and if there is one the engine will start running rough where the leak is.

I just had a similar problem. The engine is running rich and the excess fuel is igniting when it reaches the cat. The O2 sensor doesn't do anything until the engine reaches operating temperature and since you said the flame happens about 45 seconds after you start it, the engine can't be reaching operating temp. Something is causing fuel to be unburned. Confirm that the plug wires are in the proper firing order. After running the engine for a short time, remove the spark plugs and check to see if they are wet with fuel. If you find any that are wet, the cylinder that the plug came from will be where you need to take a closer look. Myself, I found two bad plug wires for cyl's # 1 & 2. Both of those plugs were wet when I removed them. You can also unplug the injectors one at a time while the engine is running and listen for any change in engine. With the engine off, you can check the resistance of each injector using a multimeter set on the 20 ohms scale. Unplug the injector and put one meter lead on one injector pin and the other meter lead on the other injector pin. Each injector should read approx. 15 ohms. Good luck.