I'm at a dead end. Have a 03 caravan with 3.3 that started to have a rough idle while in gear. It acts like there is a miss. When I accelerate it hesitates then goes. One time it started to backfire a little. It is throwing no codes. It also seems to be worse when there is a load on the motor, ie A/C and blower on. What I have done is changed spark plugs, wires, cleaned throttle body and AIT, new throttle position sensor, checked for fraying wires and vacuum leaks( which were none). My question is there anything to look at that won't throw a code? Thought about battery and alternator, but I would think those would throw a code. I haven't checked the battery because I need to buy a new meter. Any help is appreciated.

What are the cylinder pressures?

Haven't checked. Wouldn't that throw a code?

Fuel pressure is easy to check too.

Bad injector throwing too much fuel won't throw a code, just replaced one in an 02 3.3, it was so bad it filled the cylinder with fuel.

When I changed the spark plugs there were none that were wet. Also forgot to add I ran some sea foam in the gas.

Actually any missfire or even a weak cyl should set a code. Has the battery been unhooked lately as it sounds like the addaptive numerator needs to be reset. Unhooking the battery can cause it to loose count and it wont set a cyl missfire until the PCM relearns the addaptive numerator which is how the PCM learns how to count the crank sensor. It wont be able to set missfire codes until it relearns the addaptive numerator so it can count the crank sensor numbers. It usually will reset during a few decells from about 60 mph. Have it put on a scanner to see if the crank sensor is counting because any type of missfire should set a code. Heck I had a Caravan that only had a weak cyl as it was not a dead miss and most people would not have even felt the slight lope. But it kept turning on the check eng lite so the cust brought it into the shop. Ended up having a bent rod causing one piston to not come up as far in the cyl having lower comp. It still fired and was not a dead miss but the crank sensor could see it and set a missfire code. Ron

I had unplugged the battery after I changed the stuff hoping the computer would relearn. But it didn't change. I just checked and battery an alternator are working fine. Thanks

Coil pack?

This,

Usually if it does it mainly under light loads. Its either plug wires or coil pack. Seen in dozens of times.

Yep, make sure all the components in the ignition system are working properly. And did you mention that you cleaned or changed the IAC (Idle Air Control)?

When chasing gremlins like this, I like to go to a pick-a-part yard and find a vehicle like the one you are working on that has new parts and pull everything that is even remotely likely to cause an issue. Usually $25 to $50 will get you a couple hundred dollars worth of parts.

Yes I cleaned the IAC. Yeah I was thinking that too.