Hello! I am posting here because I am at my wits end! I am a 24 year old college student. My 97 Jeep Cherokee Country started running rough a few days ago. I bought it a year ago and changed all the spark plugs. The code popping up continuously is P0204: Fuel injector circuit open cylinder 4. I have replaced:
-#4 spark plug
-#4 fuel injector
-#4 fuel injector connector (tested and is getting volts)
-all plug wires (firing order is correct)
-distributor cap (rotor arm cleaned)
-added Lucas fuel injector cleaner to gas

I just don't know where to look next! I can't afford a garage. I did all the above myself thanks to YouTube with $138. I have read the TPS sensor can trigger misfires...Anyone out there run across this and have any ideas as to why it is still misfiring?

 

How did you test it? Noid light?

 

I went to O'Reilly auto parts and they scanned for codes and used a little plug to put into the connector. When the car was on it flashed.

 

That's a noid light, and it should mean that all is well with the computer and wiring to the connector. Very strange. Was the replacement injector new or used?

 

I bought the injector brand new. While the car is running I can unplug and plug back in the #4 connector to the injector and no change happens to the idle. What else could cause this if the connector has power and the injector is new? I have tracked all the wiring and it seems to look fine and undamaged from what I can get access to...

 

If you have access to an ohmmeter, I would measure the resistance across the injector. An alternative would be to swap the connectors between #3 and #4 injectors, and see if the problem stays with #4. If so, I would have to lean toward a computer problem.

 

It is a strange problem, for sure. Maybe someone else has some more input.

 

You certainly have addressed the usual suspects.

If you can unplug and plug the injector connector with no difference, you have an issue getting an injector signal to that injector. I'm confused as to why a noid light would show that the injector is firing; that is contrary to what you are seeing.

I am still leaning towards a wiring issue with that particular injector. If you completely eliminate wiring, it could be a computer issue, but that would be the last thing I would suspect for a single cylinder injector problem. If it comes down to it, get a salvage yard computer.

 

The following is from a '97 FSM. I used the figures with the splices since the connectors should be evident if you can locate the splices. Hope it helps out. If I copied in anything wrong I'm sure it'll get noticed pretty quick...


__________________________________________________ __________

__________________________________________________ __________

__________________________________________________ __________

 

Thank you all so much for your help! I was confused when the noid light worked too, I was for sure the connection wiring must be bad.

 

The misfire happened when I was driving up a hill. It started to bog down and started misfiring ever since. It has been 4 days since it happened...

 

Visually inspect the related wiring harness, look for any chafed, pierced, pinched, or partially broken wires. There have been reports of wire chafing in the harness as it exits the harness manifold (left side of vave cover).

Visually inspect the related wiring harness connector. Look for broken, bent, pushed out, or corroded terminals.

Perform a wiggle test of the wiring harness and connectors while the engine is running. Listen for the engine to miss or stall

 

Any chance it could be bad gas? I filled my tank full RIGHT BEFORE it started to misfire...one of my friends said they got a bad batch of gas which caused their truck to run crappy for a few days until they got fresh gas...

 

I don't think so. That would be more likely to cause things like multiple-cylinder misfires, etc., rather than an indicated electrical problem with one specific injector circuit.

 

Y'all find a solution to this one? Got the same problem on mine replaced tps replaced injector and traced wiring looking for bad spots...no luck yet