1994XJSport4.0

Hi all, first post for me. My Cherokee has a problem surging when I'm driving it, just started about a week ago after I took it wheeling. Starts up, and idles fine, but once i start accelerating, it'll fall on it's face. If I give it just enough throttle to keep it going it's fine, but if I get on it at all or try going up a hill to the point where it'll kick down into the next gear and rev high, it starts surging bad and i have absolutely no power. It mostly does it at the top of second gear and the bottom end of third gear, I just dropped the trans pan and put a new filter in about a week before this started happening. Since it's started, I've replaced Plugs, Wires, Distributor Cap, Fuel filter, Air filter. I cleaned the throttle body, cleaned all the intake, put new terminals on the battery cause I had a bad connection before too. tested the fuel pump, checked all the fuel lines, checked all the vacuum lines, cleaned the IAC sensor, and still it persists. Any help or insight would be appreciated. Also, if nothing else is suggested, my next step will be to change the rotor as well.

Crazy 8s

How did you test the fuel pump? Did you check fuel pressure at the rail?

You might test/check the Crank Position Sensor (CPS) also. MAP sensor might need some attention...check that its vacuum hose is not damaged or clogged.

1994XJSport4.0

I didn't check any specifics on the pump, just pulled a fuel line off at the filter and turned the key to make sure it was working steady. MAP sensor vacuum line is good, how would I go about testing the CPS or MAP sensors?

Crazy 8s

The first thought I had when reading your post was that you might have low fuel pressure. You might check fuel pressure at the valve on the fuel rail.


For CPS test..


Map Sensor

Crazy 8s

If you don't have what you need to check fuel pressure, you can borrow some stuff from Autozone to help. $150 to borrow it, but you get it all back when you return it.

http://www.autozone.com/loan-a-tools...diagnostic-kit

1994XJSport4.0

I've got another fuel pump laying around here somewhere, I'll try that before I rent the test kit. I'm about to go out and test the MAP though.

1994XJSport4.0

I had just replaced the fuel tank with one from a 1996 and was suggested the breather line could be clogged and that it could be creating a vacuum in the tank.