Codes & Misfire!!! Need dianostics gurus please!

1994 Cherokee 4.0
Ok new XJ new problems. I have a BAD misfire on #3 & #5 cylinders-- I replaced cap, rotor, plugs and wires. Still misfiring... I know it is #3 & #5 because I can pull those plug wires off the cap and no change in idle.. pull any other plug and idle gets worse. and no, they are not cross wired-- I triple checked

The CEL is NOT on and has never been on since I bought the vehicle.
But it does have codes with the key switch method.

11-No ignition (CPS) reference signal detected during engine cranking

( if the CPS was bad it wouldn't start at all right?)

13-No difference is recognized between the engine MAP reading and barometric pressure reading at engine startup.

hit enter too early and posted the message...

anyway..

I dont think there is anything worng with the MAP sensor... when I pull the vaccuum hose off of it the CEL comes on...

the last code it throws is

17-Engine Coolant Temperature remains below normal operating temperatures during vehicle travel
(this is not causing the motor to run as rough as it is)

so-- the question is: would a bad CPS cause it to misfire on just two cylinders? or do they just go bad?

If it is not electrical, looks like its time to pull the compression gauge out..... any suggestions?

1. Crank sensors usually are all or nothing, but not always. Still could be a crank sensor issue. But code 11 can also be the CAMSHAFT position sensor so don't get tunnel vision that it has to be a crank sensor issue. Cam sensor can be tested and is located inside of the distributor.

2. Map sensor can be tested

3. Coolant temp sensor can be tested

Bottom line is that you should adopt a methodical "testing" based strategy to sort
out the root cause of your codes.

birchlakeXJ said:

1. Crank sensors usually are all or nothing, but not always. Still could be a crank sensor issue. But code 11 can also be the CAMSHAFT position sensor so don't get tunnel vision that it has to be a crank sensor issue. Cam sensor can be tested and is located inside of the distributor.

2. Map sensor can be tested

3. Coolant temp sensor can be tested

Bottom line is that you should adopt a methodical "testing" based strategy to sort
out the root cause of your codes.

Click to expand...

Agree.

Also, test for 12 volts to those two injectors, then test for the negative signal from the PCM for the firing pulse. A lack of power or the firing pulse ground could be the synch sensor (CMP) or the PCM, or there is a sometimes flaky spot in the injector harness near the back of the valve cover/firewall, about where the harness takes off to the synch sensor in the distributor.

10-4-- I'll check it out... where can I find the pin-out chart for the PCM so I can check for current from the PCM?