Hey everybody, Im Mark, and I have been working on this 1991 Jaguar Sovereign 4.0 for awhile now and i cant seem to get it running right...since august... lately i found out that it wont even start up unless i disconnect the coolant temperature sensor (very weird) I've replaced everything that might be causing it to stall, and when i do get it running i have to keep my foot on the pedal and then it starts popping through the intake, if i let go of the pedal, it stalls.... please help!

Everything here i replaced and checked...

New Fuel lines
New Fuel pump
New Fuel regulator
New Fuel filter
New Mass air flow sensor
New intake manifold gasket
New idle air control valve -(programmed)
New plugs & wires
Checked catalytic converter
Checked distributer
Cleaned throttle body
Cleaned injectors
replaced computer ECU

what can be causing it to do this?

 

Marco, from what you are describing, it sounds like you have 2 plug wires that are crossed and you are having a cylinder or two fire at the wrong times, leading to the backfiring through the intake. From there, it is possible that you have managed to get the timing off a little. The timing chain may have jumped a tooth and that is causing your problems.

 

thanks for the response thermo, i will check this and fix it, ill report back soon

 

Also, you missed the one thing that'll stop an XJ40 in its tracks: a crank position sensor.

 

Rld14:

I plan on taking a look at that! Could be the culprit