Chrysler Repair: 1994 Chrysler Concord - starting and stalling problem..., chrysler concord, exhaust gas recirculation

Question
So here is the entire low down on my car issues... 1994 Chrysler Concord, 3.3L engine, over 250,000 miles. Just recently the car was bucking and backfiring so I checked the codes with the ignition key and the O2 sensor was bad. The car was also in dire need of a tune up, so along with replacing the O2 sensor, the spark plugs, spark plug wires, fuel filter, air filter, oil filter and oil were replaced at a small town car repair garage. I drove my car home ( 12 miles ) and it ran perfectly fine, showing none of the problems it had before. So, a few hours later, I get in the car to leave home, start it up and when it starts, it smells like a rich mix of gas and exhaust and it's running a bit rough. I try to drive away and the car stalls. Try to start it up again and nothing. It will turn over, but it won't actually start the engine. If I put my foot on the gas and press it flat to the floor it will start, but as soon as I let off of the gas pedal, it will stall out again. Try to restart the car and the whole cycle starts all over. If I let it sit for awhile ( more than a few hours ) it will start again no problem, but again, if I try to drive away, it will stall and not want to restart without smashing the gas pedal to the floor.

The starter and alternator were checked and they are fine. I just put a brand new battery in the car the day I brought it back from the shop and I checked the fuel pressure via the valve on the fuel rail and it is fine. There are no codes showing up with the ignition key either.

Answer
Hi Crystal,
Are you at least getting a 55 code from the key readout? If not, then we have the possibility of a problem with the engine controller or its battery supply circuit. Assuming that you are getting the 55, then the issue is probably one of an improper fuel/air ratio causing a too lean condition. There is one part which will cause that without setting a fault code: the exhaust gas recirculation (egr) valve.
I would take a look at the exhaust gas recirculation valve which is located behind the engine near the air intake throttle valve. It is mounted in a pipe that runs between passenger side exhaust manifold and the air intake manifold. The valve is mounted horizontally and has a valve stem between its round vacuum actuator top and the body of the valve attached to the pipe, inside the flange that connects the two parts. The stem has a slot into which you can insert the tip of a flat-bladed screwdriver so as to lever the stem back and forth against spring-action which should move freely and close it tightly. If the stem seems to be sticky so that stem doesn't close all the way by spring-action, then you can try spraying some penetrating solvent like WD-40 on the valve stem to free-up its motion.
If the valve is sticking slightly ajar it will make for a rough idle or no start such as you describe because the mixture is too dilute. It is one of the most common causes of this symptom. So see if you can find the valve and check/lubricate the stem. To check it in motion you can rev the engine from idle to 2500 rpm and back to idle and watch to see if the valve stem moves freely in both directions to the extreme open and closed positions. It may be that the interior of the valve is cruddy so that might require that it be unbolted from the pipe where it it attached and cleaned. But chances are good it will only be a sticky stem. Feel free to write back with the results and other questions you might have.
The other approach would be to have the car towed back to the shop that did the tune-up and let them figure out what they overlooked.
Roland