i have a mitsubishi eclipse 1993 and its running too lean my old smog paper said the hc's (hydrocarbons) are too high. would a egr valve temp sensor make it do that if its fualty? or could it be someting else?
A faulty EGR sensor or the EGR valve itself would definitely make the car run lean at idle. The sensor regulates the amount of EGR opening at various coolant temperatures and manifold vacuum if it's vacuum actuated. If the diaphragm under the EGR valve has ruptured you'd get a straight vacuum leak plus lean condition if vacuum actuated. There's a simple test for EGR valves. Place a length of tubing on the valve port and dray vacuum with your mouth. Reach under the valve till you feel the rubber diaphragm. If the valve opens you'll feel it with your fingers. If it doesn't move the diaphragm has a hole in it.
Hydrocarbons are caused by an incomplete burn in the cylinder on the power stroke. An EGR can possibly be the problem, but so could a bunch of other things. I suggest taking it to a good shop and let them figure out what is wrong. If you guess, you could literally spend hundreds of dollars on things for your engine that won't make any difference at all. Look for ASE certified shop is the best.
To man Hcs means you car is running Rich not Lean but yes an EGR can cause that an egr takes the exaust gasses and recirculates it back into the manifold soo if your lettn a few hcs outta the exhaust valve then the erg would recirculate it but there is plenty of other reasons for your car to runn to rich
