Severe stumble, misfire and no start issues

[RCP Phx]

At this point, my money is on the front O2 sensor. My XJ ran totally rich and like crap when it went bad.

:roflmao: There is only one!

 

[maxbraketorque]

:roflmao: There is only one!

Great. No chance to replace the wrong one. But yeah, I've not paid much attention to the older XJs.

 

[Saudade]

 

[n3squ1ck]

Ok im getting depressed now...

Changed the IAC
Changed the O2 Sensor inkl. Relay
Changed the CPS

NOTHING!
The issue is still the same....

I really start to think the car just wants to gently kill me...

 

[n3squ1ck]

I really try to find anything left that could cause this...

Could a cracked exhaust manifold cause this?
The cat? if so how can i test it?
A broken silencer?

What could it be...

The "deleted" EGR Valve leaking / sucking air into the manifold and killing the ratio?

Im out of ideas

 

[maxbraketorque]

I really try to find anything left that could cause this...

Could a cracked exhaust manifold cause this?
The cat? if so how can i test it?
A broken silencer?

What could it be...

The "deleted" EGR Valve leaking / sucking air into the manifold and killing the ratio?

Im out of ideas

As far as air leaks go, since your plugs indicated a very rich condition, an air leak would need to make the ECU push fuel to a rich condition. Air sucked into the intake manifold will cause a lean condition. Air sucked into the exhaust manifold will cause rich.

I have heard of a few XJs having clogged cats. I'm sure that would cause poor running, but its not obvious to me that it would cause a very rich condition.

 

[n3squ1ck]

As far as air leaks go, since your plugs indicated a very rich condition, an air leak would need to make the ECU push fuel to a rich condition. Air sucked into the intake manifold will cause a lean condition. Air sucked into the exhaust manifold will cause rich.

I have heard of a few XJs having clogged cats. I'm sure that would cause poor running, but its not obvious to me that it would cause a very rich condition.

Whats confusing to me is the following:

If it is running rich (map hose unplugged) its running fine, and i guess thats the reason the plugs were black, they had 50-100 miles on them and all of that driven time without the map -> running rich

The issue exists just if the Map hose is plugged in, wich leads me to believe its running to lean thats why im leaning toward a vacuuum leak (somewhere around the intake manifold) the whole vac harness is new

So youre saying if i had a crack in the exhaust manifold that would cause a rich condition?

I thought about ripping out the cat and looking inside, i just fear i dont get it out without damaging it

 

[maxbraketorque]

Its situations like this when a standalone wideband O2 sensor would be informative.

I guess you've checked the easy-to-address intake manifold vacuum leak locations? I suppose the tough location is a leak at the gasket to the head.

I think that pouring water through your cat would be sufficient to assess whether its plugged.