I have a 91 xj 4.0 auto that starts but won't stay running. It has sat for a couple of years. If you put your foot in just the right spot on the throttle it will rev up when it starts but dies right away. Any suggestions?

 

Could be a lot of things but I'd guess it's either a fuel or fuel delivery issue given the two-year hiatus. Start by draining the tank, replace the fuel filter and fill'er up with new gas.

If that doesn't work then it's S.O.P. for these things... do a full tune, plug wires, plugs, oil, filter, air filter, check vacuum lines and replace if there's any doubt, clean throttle body, check cap and rotor, check for strong blue spark, check fuel pressure at the rail, replace CPS.

If that doesn't work then test your TPS and MAP, adjust or replace as necessary.

 

There's a ballast resistor for the fuel pump on teh driver's side inner fender near the air cleaner. It's white and about 3 inches long with a wire plugged into each end. Make sure the wires are on snugly and rodents haven't eaten the wires.

 

I had a similar problem with my '88 XJ years ago. I would not idle unless you stepped on the gas. Turned out to be the little motor on the throttle body called the air-idle-control-motor. You might check this too.