I'm not having much luck with other forums so I hope I'm not to out of line asking a question today for my van and not my truck. 1998 4.2 motor with 230000 miles. Started throwing code PO 303. Couldn't locate problem for a couple of months. Then PO141. Next PO113. Now PO301. Compression good. Wires, plugs, and coil test fine. Checked air temperature sensor connector and had 6 volts. Checked injectors with a stethoscope and they all sounded the same. Not sure where to check next. Any advice would be appreciated. Thanks

 

You have to look up all the codes and see what part of the systems they are referring to.
Codes:
113 is open circuit in intake air temp sensor. Is the plug on tight and does the sensor test good?
141 Ox sensor "heater" circuit open bank 1 sensor 2. This is the rear sensor on the passenger side. Is the plug on or the harness rubbed open at some point or the heater open?
Check only the heater leads. Do not measure the sensor it'self.
301 is cylinder 1 misfire.
303 is cylinder 3 misfire.
These are first and third from the front on the passenger side back.
Look at the plug wires first then suspect the coil.
You have more than one issue causing confusion.
Address one at a time and clear until they are all gone and engine starts and runs smooth.
Good luck.

 

I tried new plugs and wires. I tested the coil with ohm meter and checked out with manual. Temp sensor was supposed to be 5 volts (was 6) which pointed to PCM. I'm guessing misfire in 3rd has messed up oxygen sensor. Van was bullet proof till lately. Could coil test fine but be bad? Intake temp sensor is easy to replace but I don't want to throw parts if it's PCM. Thanks

 

Don't rely on resistance measurement for the coil.
If your sure the wires are good try a coil.
No spark is no spark.
On the IAT, the PCM supplies several sensors from the same supply.
All your issues almost seem as if the PCM connector is loose or corroded.
Try reseating the PCM connector.
Good luck.

 

Put in a new coil. 1/2 mile codes 303 and 141 went off. Is reseating the PCM removing, cleaning surface and installing. Thanks

 

Reseat the connector only.
Good luck.

 

Removed connector, sprayed electric cleaner and applied dielectric grease (appeared spotless). Threw PO303 and PO141 again. Still willing to keep trying. Thanks

 

You have one cylinder #3 as a misfire.
Put a spark plug on the end of the wire and lay the plug body on ground.
Start the motor, is there spark or not?
If yes, then the cylinder may be in trouble. Burnt valve or even a head gasket or even the PCM that fires the coil for that cylinder.
The 141 is a totally separate unrelated trouble.
The sensor heater circuit is open.
Test with a voltmeter for voltage at the sensor socket.
There are 4 sensors. With only one in trouble you have to see the issue close by.
Work to eliminate all these possibilities.
Good luck.

 

Removed plug and received continuous spark. Normally I can figure out my vehicle's issues, but this has been a real pain.












Pulled plug and had good spark. How do you know if it's a valve or head gasket. It's not leaking antifreeze. Has good compression. Thanks

 

You have something wrong with that cylinder.
Make a compression test and compare it to the rest.
A 303 code is a misfire for any reason, not just the lack of spark.
The misfire code is set when the crank sensor detects a rotation time as to slow compaired the average of all the rest of the cylinders.
The computer has no way to know 'why'.
It could be lack of fuel, spark, cylinder compression is low, blown headgasket etc.
Good luck.