1998 Regal 3.8 P0401 & P0171

[Hotwheels]

Hey guys,

I've got an intermittent problem here....

On my '98 Regal 3.8, I've got an intermittent stumble at normal acceleration, only when the car is partially warmed up (at the 1/4 mark range on the temp gauge). It never occurs when started from cold, or when fully warmed up. When it does happen, the car coughs a few times under acceleration, for probably a city block or two, then goes away as it warms up. If I stop while it is acting up, I get a rough idle. It's set a check engine light, which bounces between P0401 Insufficient Flow EGR and P0171 Fuel System Too Lean Bank 1. I can reset the code, and even with no symptoms, from a cold start, the SES light will come back on in a few blocks, and will alternate between those two.

I'm guessing I've got a bad/clogged EGR valve, as it only acts up based on engine temperature (halfway warmed up). Am I on the right track? A buddy at work picked me up a good used EGR off of another Series II 3800 to try out. Are all Series II EGR's interchangeable? Are there any other things I should check for, or should I try cleaning either of these EGR's (if so, what is the best way to do that)?

(Btw, the car only has 133k and was a 1-owner car prior to me buying it - I only drive it 2 miles to work, so it's likely seen a lot of short trips in its life - likely to have carbon issues).

[Hotwheels]

*crickets* ....

[bs009]

EGR should be interchangeable among 3800's. As long as the connector is the same and it's not off a 60* v6.

[harofreak00]

Also check the tubes for cracks.

[Hotwheels]

Replaced the EGR with a good used one out of a good running '99 Grand Prix with under 100k, and a coworker had a spare screened gasket. I'm still getting the same symptoms and codes coming back. I forgot to check the tubes - should that be my next step? What else should I look for?