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Chrysler T&C runs rough for first minute then smooth

I have a 2002 Chrysler T&C AWD Limited 3.8L with 175K on it.

It will run rough for the first minute after sitting overnight,then clear up and run normal. It only does it when it has been sitting for more than about four hours…the longer the sit the rougher it runs for that first minute. Exhaust is slightly smoky for that first minute. The engine light came on right after the second or third rough start. I did a one tank techron fuel treatment, but did not notice any difference.

Dealer Maintenance(mopar)history is as follows:

5/08(133K)Tune-up, replaced wires, plugs, up & downstream 02 sensors.Clean throttle body.

6/08(135K)Replaced fuel pump and filter.

3/09(153K)Code cyl.#3 misfire - Replaced #3 plug and wire.

6/09(158K)Code cyl.#3 misfire - Switch injector #3 with #5.

10/09(165K)Replaced upsteram 02 sensor.

3/10 (175K)Multiple misfire including cyl#3. Cause not determined yet.

I would appreciate any suggestions you might have. Thank You

Someone should check the compression - needless to say paying special attention to cylinder 3.

Someone should also check the fuel pressure and the fuel injectors and fuel pressure regulator for leaks.

Unless it is for warranty or recall service you don’t need to use a dealer.

Try this and see if it makes a difference:

Tomorrow morning turn the key to “ON,” wait five seconds (count slowly), then turn the key to “START.”

The five seconds gives the fuel pump time to pressurize the system. You could be losing fuel pressure overnight.

moparadise - Thank you for that suggestion. I will give it a try and will get back to you with the results.
Thanks again , Frank

cigroller - Thank you for the advice…will follow up as suggested if pressurizing the system prior to start doesn’t do it. Thanks again, Frank

moparadise - I tried it last night and I seemed to notice less rough but still some…so I tried it again this morning but gave it a little more time…about 20-30 seconds in the on position and it ran normal…no misfire. Based on this, what do you think the next best course of action is. Thanks again, Frank

I think that someone needs to put a fuel pressure gauge on it and figure out what is going on with the fuel pump/pressure. You might end up replacing it again. That said, the method has to do not with how long the key is in the on position, but how many times you turn it from off to on. Each time you go from off to on the fuel pump runs, but only for a few seconds. It matters not how long you hold the key on. So turn it to on - wait 5 seconds - turn it to off - turn it to on - wait 5 seconds - etc. Each time you should be able to hear the pump hum if you listen.

I’m still wondering, however, why cylinder 3 keeps popping up with a problem.

This sounds like a loss of residual fuel pressure to me.
The slightly smoky exhaust could point to an injector or fuel pressure regulator leaking off.
Has anyone unplugged the fuel press. regulator vacuum hose and inspected it to see if gasoline is present in the hose?

Another possibility is the check valve in the fuel pump but since this has been replaced that should be a non-issue.

However, at 175k miles maybe the smoky exhaust upon startup is not related to this problem and could be related to the valve seals instead.
Hope some of that helps.

How does plug #3 look? Any coolant loss?
Could be head gasket leaking coolant into #3.

To everyone - Thank you for helping me out. I have been doing the on/off fuel pump 2X prior to morning starts and no misfire, runs smooth, no more slightly smoky exhaust either…must have been from the rough start with low pressure. The engine light has gone out. I will let you know what the culprit was when I get it fixed.
Thanks again, Frank

I was told by a local guy that a faulty gas cap could cause fuel pressure to bleed off. I looked at mine and the spring inside seems fine…just wondering if this is true or how probable.

The gas cap has zero to do with residual fuel pressure and the local guy is utterly wrong. Fuel pressure is maintained while the engine is at rest by 3 things; closed and non-leaking fuel injectors, fuel pressure regulator, and the check valve in the fuel pump.

The usual suspect is the check valve and this means a new pump. A worn check ball or ball seat, piece of debris stuck in there, etc. is what usually causes these to leak.