I just bought a 2003 3.9L Auto van. 100K on the clock. When I picked it up it would not idle at all. Today I removed and cleaned the IAC and it now idles but very rough. So I replaced the oil, oil filter, air filter, wires, plugs, cap, rotor, flushed cooling system and cleaned the PCV out. Still having same rough idle problem.

I tried pulling each spark plug wire and all seem to make idle worse so could not locate a dead cylinder. Also all plugs pulled looked black and sooty but not that bad.

It had not codes present.

Any ideas?

Thanks!


-Mike

 

Replace the ignition coil.

 

Remove and throughly clean the TB especially the IAC port.

 

Try this, give the engine the "finger trick" (actual term told to member Stev by a Dodge technician). With the engine cover and air cleaner top removed start the engine then where the idle air port is (just behind the throttle plates) put your finger over the hole and start to choke/close off the hole. This will make the PCM draw in the IAC motor to full open position. Now close off the port to stall the motor. Once the engine quites leave the key turn on but disconnect the battery. Wait about 5 minutes then reconnect the battery and just turn the key to the "on" position, don't try starting it just yet. Wait for a 5 seconds then turn off the key. Wait again about 5 seconds then turn on the key and start the motor. See if now that it runs better.

Hope this helps
Kenny

 

Here is how to easily clean the IAC step-by-step ...

https://dodgeforum.com/forum/dodge-r...n-the-iac.html

 

Stev, he already did that. First line towards the end of that line. It actually helped in letting the engine run after being cleaned.

 

Today took it out for a drive on the hwy, got a code P0303
cyc 3 misfire

So........its got spark, can I assume its the fuel injector? Any help in diagnose is appreciated.

I have replaced the coil today.

 

Also
vacuum leak
Intake Plenum pan leak

Try moving the injector over one and see if the misfire code moves with it or not.

 

Checked compression on #3 today and # 5 for comparison, both are around 120psi cold. So thats not it.

Cleared code and moved #3 injector to #5 spot and put it back together. Started it and ran to operating temp with no codes...yea. Shut it down put cover on motor and cleaned up than started it again to move it in the driveway and CEL came on. Now its got same P0303 and also has P0304 and P0300. AGGGGG!!!!

 

Would that not trip a code for a lean condition like P0171 or something like that?