Trying to help a friend with his 97 4.0 auto.Check engine light on and code says open circuit on injector 1. Replaced #1 inj, plugs, wires, rotor button, compression check all 6 150 and the vacuum reading looked good. The jeep has 140k and seems in mechanically sound condition. The jeep runs rough at idle but runs great the rest of the time. you can flog the **** out of it and it runs great, it will burn the tires from a dead stop thru 2 gears but won't idle and sets off the check engine light. I tried swapping the 1 and 2 injectors and the code says #1 cyl missfire now? any ideas?

 

Try cleaning Idle Air control, Throttle position Sensor (Possibly Replacing).

 

You have done the right thing by swapping injectors.

That code is for the entire "circuit", and that includes more than the fuel injector itself.

The fact that you are still coding for an injector issue with that cylinder indicates possibly a flaky "connector" on the #1 cylinder, or a wiring issue.

If connector checks out, start tracing back the wiring for the injector for #1.

Stay with the code, and trust the OBD on this one.

 

Thanks!! I'll keep trying.

 

It might be a camshaft. When I was working a jeep I had a 4.0l come in with the same problem. Rough at idla. Smooth while running. All checks came back good, compression vacuum. Spark. Even swapped injectors to see if the problem moved. Nothing. Ran cleaners through the intake. Still nothing.....so.. there is a TSB out to pull the VC and check the pattern on top of the valvas. A circal pattern is good. A stripped pattern is bad. Meaning the valve isn't rotating. Pulled the head changed the valve. DIDN'T pull the lifter. Put it back together and still same thing. Finally pulled the lifter and it was wiped. So replaced camshaft and lifter.

Hopfully that isn't gonna have to happen for you. Best of luck. Let me know what you find.

 

DOH!!! hope its not that!!!!!

 

Any update? Found anything out?