2001 xj8 4.0 will start than die if you can get it past idle it will run if you play with the pedal Then when let it go back to idle it will surge from about 800-200 rpm a few times than dies sometimes it will smooth out and idle at about 600 rpm put it in gear usually dies any ideas.

 

This to me sounds like a fuel problem.
First, check for error codes.
Go to the trunk and hot loop the relay for the fuel pump and test fuel pressure
at the schreader valve in the inlet manifold, drivers side front.
It has a blue cap.
You also want to check operation of the throttle body and it's connections.
What codes are you getting?

 

What do you mean "stalls on codes"????

I promise the codes do not stall the engine, but rather they are designed to report the problem. So, what do the codes say?

I suspect you have a air leak in the intake plenum or breather tubes, but that is one wild *** guess without the codes.

 

sparkenzap
the on codes was a typo it should have said NO codes. A couple of hours after my first post I tried it again and it idles perfectly.

 

xjay8
I don't think it is a fuel pressure or pump problem yesterday it did idle after my original post it is not setting any codes I'm going to check my connections TB again the fuel pump was replaced 15 months ago so I'm kinda ruling that out thanks for the imput

 

OK, so it is good to know you ain't nuts!
Can your scanner give you trace graphs of the STFT and LTFT? Those are way helpful for identifying mixture problems. XJ8's recommendations about having a look at the TB connector to make sure they are clean is a good place to start.
The fact that it started working OK sorta rules out the possibility that the timing jumped- that is a good thing! You have changed your tensioners, right ?

Good luck and keep us posted.

 

sparkenzap
thanks for the info my scanner will not read STFT & LTFT but I do think I have a broken tensioner or guide on the right bank. Monday going to take it to garage a friend going to check it out can here what sounds like chain slap when rev up and when it backs down you can hear it. Hopefully can get by with just replacing the tensioners and gaskets. thanks again for the info let you know what we find.

 

Good luck, man!

 

not that I forgot about the help you gave me but wanted to make sure the problem was fixed. After taking to garage to have what I thought was timing chain slap I was pleased to find out it was the chain sensors that made the noise I was hearing. After doing some more searching on the forum I found a post showing the same problem I was having Cleaned the MAF sensor ran a can of sea foam through a 1/2 tank gas dumped in some octane booster and started running premium along with injector cleaner every 3 to 4 weeks been running great ever since.

 

Chain sensors? I don't understand.