misfire that i cant figure out

[rusty 91]

i have a 98 explorer with the 4.0 sohc engine, it runs like crap so i pulled the codes. p0302 p0305, i clipped my timing light on the spark plug wires and 5 issent fireing at all and 2 comes and goes, it will fire for a few seconds and then stop for a few seconds. ive put new plugs, wires and even replaced the coil pack. i cant figure out why its is still misfiring. im out of ideas. hopefully some one on here can help

 

[2000StreetRod]

confirm plug wires

First, I suggest that you confirm that your spark plug wires are connected correctly.

Many members misconnect the wires for cylinders 5 and 6. If the wiring is correct then check at night for arcing from the wires to chassis ground. A remote possibility is a bad crankshaft position sensor. Try cleaning the connector contacts by disconnecting/reconnecting the connector a couple times. The trigger wire connection from the PCM to the coilpack could be bad. The wire could be broken, shorted or the associated PCM pin could be pushed back into the connector backshell.

 

[rusty 91]

i did check the fireing order and it is correct, as far as the crank sensor i never thought of that, ill be working on it wed. ill be sure to check that first, also could the the cam sensors also cause a misfire?

 

[2000StreetRod]

camshaft position sensor

The camshaft position sensor allows the PCM to determine when cylinder 1 is on the compression stroke. If it is bad the fuel injectors spray at the wrong time resulting in a stale charge that can result in a misfire but the spark should still be present. I've read that the SOHC V6 usually will not start or run with a bad camshaft position sensor. I've never disconnected mine to find out.

 

[rusty 91]

OK, so I put a crank sensor in it today and no change. Does anybody know how to test the 4 small wires going to the coil pack?

 

[rusty 91]

Also I ran the engine in the dark and dident see any arcing

 

[vroomzoomboom]

what kind of plugs did you use? like brand name, and are they copper?

 

[2000StreetRod]

radio noise suppressor

There is a capacitor connected to the primary winding of the coil pack to suppress ignition noise in the radio. Sometimes it will fail causing ignition problems. It is easily disconnected. Something to try that only costs time. Measure the primary voltage with a meter to see if it is steady at battery voltage. Clean the locations on the coilpack between it and the fastening bolts.

 

[rusty 91]

what kind of plugs did you use? like brand name, and are they copper?

I'm not sure what kind they are, I dident install them

 

[rusty 91]

There is a capacitor connected to the primary winding of the coil pack to suppress ignition noise in the radio. Sometimes it will fail causing ignition problems. It is easily disconnected. Something to try that only costs time. Measure the primary voltage with a meter to see if it is steady at battery voltage. Clean the locations on the coilpack between it and the fastening bolts.

OK, I got out my digital volt meeter, and I don't think its accurate its showing I have 14 volts at the battery with the engine off. But any ways I unplugged the capacitor cranked the engine for a few seconds left the key on and checked with my meter, voltage read the same as the battery . I also removed coil pack and with sand paper cleaned up the bottom of coil and the bracket it bolted to. Put it back together and no change.

 

[rusty 91]

any body got any ideas?

 

[2000StreetRod]

PCM connector?

Did you check the PCM connector for pushed back pins on the trigger wires? On my 2000 the pins are 26, 52 and 78. Check for continuity from the PCM connector to the coilpack connector. Also, make sure the connector retaining bolt is snug but do not over tighten.

 

[rusty 91]

OK, I pulled all 3 big square connectors off the PCM and I seen no pushed back pins. I dident see any pin numbers on the plugs or I just dident see them because there really small. So what I did was took the negative cable off and unplugged the coil pack, turned my meeter to ohms and just started with the first wir on the coil pack connector and the upper most plug to the PCM. The matter showed Resistance.on multiple pins witch I dident really understand. So on the other 2 PCM conecrors I got a hit on a pin on the middle connector and nothing on the lower most PCM plug. As far as the other 3 wires on the coil pack connector I went through them one at a time with every pin on the PCM plugs and got nothing, I must be doing something wrong

 

[2000StreetRod]

PCM & connector

There is only one PCM connector.

It should mate with the PCM.

 

[bluestream1]

what kind of plugs did you use? like brand name, and are they copper?

What difference would that make??

 

[vroomzoomboom]

some ppl (myself included when i had the SOHC in my truck) have said some plugs will misfire in that motor. why, i dont know. i had i think ngk's at one time and it misfired badly. i put motocraft back in, and it ran fine.

 

[2000StreetRod]

no or intermittent spark

. . . i clipped my timing light on the spark plug wires and 5 issent fireing at all and 2 comes and goes, it will fire for a few seconds and then stop for a few seconds. . .

The original post indicates an ignition source, spark plug wire or shorted plug problem.

 

[rusty 91]

I got spark on all six now, I put new plugs in it, I talked to the previous owner and he said they weren't new , I thought they were. The wires are but for some reason he dident change the plugs at the same time. Thank you 2000streetrod for all your help. When changing the plugs I did notice the no. 1 cylinder wasent in right, it wasent in there very many threads and when I put the new one in same thing, its not in very far and the angle looks wrong, so hopefully I can run a tap in there to straighten it back out