Bad news -- It didnt fix it!!

[cardboard]

Well I spent most of the day putting a new timing chain and other new parts which I just thought I would change as long as I was that close. To my surprise it did not fix my problem now I am really up the creek because I am at a lose for what the problem may be.
Here is the specs if anyone cares to take a stab at it: Monday morning driving to work running fine, pull up to a stop light, when it turned green I step on the gas and it backfires and then I cant get over 2000 rpm and 25 miles an hour. Seems to idle ok (up and down 600 rpm to 1000 rpm) once I put new chain and gears on. I check distributor index and it is fine, I also put a timing light on it and shows 15 Degrees advanced?? :rattle:
Can someone help or give me an idea?

 

[Chasjr1]

If its older, or has quite a few miles on it, you might see if the catalytic convertor is plugged. Had a late 70's F250 that did that when it was about 8 years old.

 

[cardboard]

Nope it has no cat on it.

 

[afd516]

crankshaft positioning sensor!

 

[cardboard]

Ok, alittle up date,
Cps is new
Fuel pump is less than a 4 months old
Fuel filter is brand new
Timing chain& gears
5.0 injectors less than 1 year old
new distributor
cap rotor and wires


I just went out and started it up for the first time today , and this is what I am getting: Starts kinda slow, takes more cranking time than normal. When it does start it revs up to 1500 rpm than stalls, starts up right away again. Seems to idel fine for 2 to 3 minutes then will start up and down between 600 and 1000 rpm then it will finally die. When it is running if you step on the throttle to hard it will make it backfire thru the throttle body and if you just stay on the gas then it just slowly dies.

 

[RichP]

Stick a meter on the TPS, that backfire could have melted plastic on the sensors. Cleaning the TB with spray cleaner is iffy at best if not careful, I can imagine the effect of a backflash of hot burning fuel on them. As for the cat you could always disconnect your down pipe at the cat and fire it up, see if it has any effect. I always preferred the GM style cats with the balls in them, when you dumped raw fuel into the exhaust and got a backfire it would usually just blow the plug on the bottom of the cat and drop them out at which point could put a freeze plug in there and it was no longer a functiong cat.
Also pop your dist cap and make sure the rotor is not damaged and look for carbon tracks between the contact points on the inside of the cat. Also in the dark look for arching in the plug wires.

 

[cardboard]

No luck Rich, It has no cat and the cap dist plugs and wires are new.

 

[Tom R.]

Only time I've witnessed backfire issues with the XJ is when the plug wires are routed incorrectly. Maybe a bad computer? Did you pull up the codes?

 

[leadfoot77]

it could be your head gasket....i when to start my 01 XJ Limited and a leaking fuel injectors dumped too much fuel and popped that puppy and the same thing happend would start but ran LIke #%$@*&^%%$&^* these thing have that problem and bosch the oem injector maker is supposedly "reengineering the injector" jeep added a heat sheild on intake but its junk.. but yea look for a blow headgasket....

 

[WobblesXJ]

Check the vacuum lines, especially the ones going to the map sensor, check the map sensor.

Just a few extra things to look at.

 

[MDXJ]

pull the valve cover off look for abroken spring or two had that happen

 

[afd516]

Check your cps. Mine did the exact same thing. A bolt was missing causing it to be misaligned, causing the motor to do exactly what you describe. It is possible, being that you just replaced it that you have one that worked its way loose or you got a bum one that took a shit on you already.