Chrysler Repair: 1997 LHS codes 171/174, side exhaust manifold, exhaust gas recirculation valve

Question
Hi Roland,

my parents have a 1997 LHS with about 85,000 miles.

Symptoms:

1. Exhaust fumes in the car
2. Rough idle, sometimes dies in idle right after start-up
3. OBDII codes 171 and 174

My first guess would be o2 sensors but not likely that both would go bad at the same time.

Do you have any suggestions for me?

Thanks,
Jeff

Answer
Hi Jeff,
While there are many possibilities unrelated to the O2 sensors, I would start by checking over the entire exhaust system for leaks. The smell of exhaust suggests that is the cause of a too lean mixture being seen by the sensors. Such leaks will lean the exhaust and mess up the sensors and thus the feedback to mixture control. Also check the exhaust gas recirculation valve to be sure that it is sticking slightly ajar which will cause the hard start/rough idle as well as too lean mixture. It is in the pipe that runs off the right side exhaust manifold back toward the intake throttle body. Its valve body is mounted in that pipe and it has a round vacuum actuator and vacuum hose. Between the actuator and the valve body there is an open flange inside of which is the valve stem. It has a circumferential slot into which you can insert the tip of a screwdriver and thus move the stem back and forth. Spring-action will try to close the valve to a dead stop. If it doesn't then spray some WD-40 on the valve stem where it enters the body and work it some more.
If those steps don't do it, then low fuel pressure could be the cause, but there are several other possibilities. You can use the "thank and rate" tab to get back to me, using the 'comments' section.
Roland