I've got an odd issue I haven't seen mentioned in other threads. I have a 3.0L 2000 Caravan (205000 kms) that has a P0201 (& subsequent P0301) error, except the van starts & runs fine the first start in the morning or if it's been sitting for 5+ hours. If I were to do some errands requiring multiple stops, the engine will start to run rough (as in the P0301 cylinder misfire). I drove 250km without incident, stopped at a vet hospital for a few hours, then upon restarting the engine the van began running rough again (the necessary 250 km return trip home at highway speed with a rough running engine was a worry about causing engine damage!).

Last year I pulled cylinder 1 injector and it ohmed out as bad. I installed a BWD brand injector at that time, ran a 6500km summer vacation trip, been driving fine for months since, and never had further issues until now. The same rough running happened then, but it was always happening---NOT as a warm start issue as I have now.

I've run Seafoam, I've run Lucas upper cyl cleaner, Motomaster injector cleaner, I've run Costco fuel (which has their cleaner). I've even tried a new fuel cap (as some searches say a bad cap can throw a MIL)---I honestly don't believe the fuel cap is at fault as why have I been able to use that same cap these past 10 years. It can't be dirty injectors...

Again, I can get one good start per day and the engine runs smooth. Drive for 20+ minutes and the restart can make the engine run rough. If an injector was bad (i.e.: #1 in this case), the engine should run rough all the time (like it did last year). I've cleaned the TB, I've pulled the IAC and put a different one (used, cleaned up) on the TB (which did help with a low idle issue), and the throttle position sensor 'feels' fine (didn't swap it as it seems unlikely to be related).

Weird thing is that the past few days it's run smooth enough the PCM cleared the MIL on its own. Then, I went to pickup some takeout after I got home from work and the rough running returned and tripped the MIL again.

So! What's the gremlin in this situation?? What should I be checking next?

Hello? Does anyone have any ideas on how to help resolve this issue?

I replaced the injector. It ohmed out of range, higher than the other 5 injectors.

My theory about the cold-hot running described is this: as the injector was cold, the internals of the injector probably worked ok until the intake (where the injectors are seated) heated up the injector so it stopped cooperating. Then the engine would run rough. Since the injector was on the backside of the engine, I couldn't get a long screwdriver to the injector to hear how it was/n't ticking during idle. If I had a mechanics stethoscope with the long metal probe, I probably could have made that happen.

With the air plenum off I took the opportunity to do a few more maintenance items, most notably changing the rear valve cover gasket. That is a tight access area, and removing the alternator is necessary. If you have time to do this, it's THE time to do so as you have so much access with plenum removed. CLEAN YOUR THROTTLE BODY and your IAC port if you can. You'll need extra gaskets. Be prepared! Get some throttle body cleaner spray (I used Gunk brand) to clean stuff off. After 18 years of driving, these components get dirty!! I did a major cleaning of the air plenum too (in for a penny, in for a pound...).

consider replacing your IAC motor. Idle Air Control is a little motor controlled by the PCM when the driver takes foot off accelerator; it wears out and gets gummed up inside the throttle body.

Its been a week since the reassembly and the Check Engine light is off and vehicle is functional again.

i hope this helps others with similar P020x/P30x errors.