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2002 Dodge Stratus w/P171 code, trouble starting, check engine light

My “mobile mechanic” is stumped! I took my car to have a tire repaired and since I was noticing a “slower” start in the mornings, I went ahead and got an overdue tune up. I’ve have problems ever since: slow starts where the engine starts but shudders and sputters out several times before it “catches.” An immediate check engine light when I start driving (although after he resets the check engine light it might take 5 to 15 minutes for it to come back on the first time I drive it). Sometimes I have to start the 3 or 4 times first thing in the morning. After it finally starts, if I turn it off and restart it, usually there are no problems starting. It’s after it sits for 8 hours that it may have problems restarting, and that afternoon problem is happening more often.

I now have a new O2 sensor and new spark plugs. My mechanic says that fuel pressure jumps right up to 52 or so and stays within 55-60 during testing, so he says it’s not the problem. There are no MAP sensor or O2 sensor errors.

Today he switched the relays on the fuel pump and ASD and we drove it. It started fine, but the check engine light still came on after 10 minutes or so. I still have to test whether it will start in the morning or after a day of sitting.

So, what could be causing the P171 “lean condition”, check engine light, and the slow/no start problems? What is the mechanic missing? He’s suggesting it could be the timing belt or fuel pump- both costly. He doesn’t want to “throw parts at it” but is afraid he won’t be able to figure this out without doing that. I can’t afford that kind of repair approach!!


P0171- cylinder bank one running lean. My guess is you have a vacuum leak. Maybe something was not put back on properly when the spark plugs were replaced. Sometimes a lot of things need to be removed to get to the spark plugs on a FWD V6 car.

Thanks for the reply. My mechanic says “all vacuum leaks occur at the engine” and he can’t find leaks. He wants to check the ECT (engine cooling temperature sensor) and also wonders if the thermostat is stuck open.

Additional nfo: when I start the car and it finally “catches” there is a lot of shuddering and shaking until I hear a whir - like surge - and then the car stops shuddering, idles great, and drives wonderfully. Could this be a timing belt problem? What about a fuel pump problem, despite the fact that he tested the fuel pump and got the results I mentioned in the first message?

OK- in case anyone else was stumped and wondering what the problem was: my new mechanic took everything apart and clean the engine. Put it all back together and voila, no CEL, no lean code. He thinks there were probably a leak somewhere. He also flushed and replaced the coolant. $184!!

He may have knocked off a vacuum hose or a electrical plug somewhere when he was working on it.