Vehicle is stalling and back firing

that autozone sales person should have asked when is the last time it had a tune up... ie, spark plugs etc...

reset the ecu/ecm and clear the codes... see if the same codes come back to verify

look for vacuum leaks first if you already done a tune up by changing those worn spark plugs, etc
P1123 Hyundai Long Term Fuel Trim Error System Rich

P0108 MAP Pressure Circuit High Input

and the 0300's have something to do with your ignition components; i'll let you google those since i googled the first 2 for you

From a reputable repair website:


P0351 - OBD-II Trouble Code

Auto Systems and Repair

Ignition Coil "A" Circuit Primary/Secondary Malfunction Our emissions expert has put together the following information about the P0351 fault code. We have also included diagnostic procedures you can take to your repair shop if the mechanic is having difficulty analyzing the code.
OBD II Fault Code

• OBD II P0351 Ignition Coil "A" Circuit Primary/Secondary Malfunction

What does this mean? The ignition coil or coils are responsible for igniting the air/fuel mixture inside the combustion chambers. Without reliable performance from the ignition coil(s) the vehicle will stumble and misfire.
Code P0351 indicates there's an electrical problem in either the primary ( the computer side ) or the secondary ( the spark plug side ) of the Ignition Coil "A" Circuit.
Symptoms

• Check Engine Light will illuminate
• Engine idles rough
• Engine misfires on acceleration
• In rare cases, the engine may not exhibit noticeable symptoms

Common Problems That Trigger the P0351 Code

• Defective Ignition Coil(s)
• Defective Spark Plug(s)
• Intake Manifold Vacuum leaks
• Carbon buildup in the Throttle Body air passages
• Defective Idle Air Control Valve or Electronic Body

Common Misdiagnosis

• Ignition coil(s) replaced when cause of the malfunction was a vacuum leak
• Spark Plugs replaced when cause of the malfunction was a vacuum leak

Your vehicle does not have a IAC valve ! Your vehicle has electronic throttle control . P0351 probably a wiring issue or open driver inside the PCM for cylinder # one . Your best bet take it to the dealer , you have not the knowledge or tools to diagnose this problem ! You are obviously using some cheap code reader to pull codes with or you wouldn't come up with P0508 . Factory service info. does not show Po508 for that vehicle. Plus working for ford i know for a fact this vehicle does not have IAC . If the driver inside the PCM is bad it will need to go to dealer anyway for programming .

Sorry to tell you that it is incorrect gear ratio codes. Must replace the transmission.

did you replace coils to spark plugs,351-coil #1,352-coil#2,#3

you can check here and tells you what these codes mean www.obd-codes.com

Do you mean P0351, P0352, P0700? (The "P" makes a HUGE difference - it could also be a "C" a "B" or a "U") When you post fault codes, please be sure to post the ENTIRE fault code.

Anyway, P0700 is a generic code that is output by the Engine Control Module (ECM) to let you know that there are transmission faults present in the Transmission Control Module (TCM). To find out what the problem actually is, you must have a scanner that is capable of accessing the TCM and retriving the codes. NOTE: a "generic OBD" code reader cannot do this.

P0351 is "Ignition Coil #1 Primary Circuit"
P0352 is "Ignition Coil #2 Primary Circuit"

The ignition coil primary circuit is monitored when battery voltage is more than 8 volts during cranking or more than 13 volts with the engine running at less than 3000 RPM, and no coil in dwell during testing. The Diagnostic Test Code (DTC) will set in the Powertrain Control Module (PCM) memory when the PCM senses peak current is not achieved with battery based dwell plus 1.5 milliseconds of diagnostic offset. DTC P0351 and/or DTC Po352 takes less that 3 seconds to set during engine cranking, or up to 6 seconds with the engine running. Possible causes for these DTCs are : Intermittent condition, defective ignition coil (or coils), defective connectors or wiring,defective PCM .

NOTE: Intermiitent failures or problems in the contacts/circuits of the Auto Shutdown (ASD) relay can also cause these codes. Some aftermarket equipment , like remote starters and antitheft systems that are connected to the ASD relay circuits can also cause these codes. Any such equipment should be COMPLETELY removed from the vehicle before attempting to diagnose these codes.

P1391 - Not a valid obd code.
B1391 - Oil Level Switch Circuit Failure
C1391 - Not a valid obd code.
U1391 - Not a valid obd code.
Its possible you may have misread this code. If it is B1391 that would be the only code with 1391 for your vehicle.

P0351 - Ignition Coil A Primary / Secondary Circuit Malfunction. The ignition signal from the Powertrain Control Module or Electronic Control Module is sent to and amplified by the power transistor. The power transistor turns ON and OFF the ignition coil primary circuit. This ON/OFF operation induces the proper high voltage in the coil secondary circuit.

Possible Causes:
- Open or short in the ignition coil circuit
- Ignition coil circuit shorted to ground
- Ignition coil connector
- Damaged ignition coil
- Damaged PCM

P0352 - Ignition Coil B Primary / Secondary Circuit Malfunction.
Same repair info as P0351.

P0353 - Ignition Coil C Primary / Secondary Circuit Malfunction.
Same repair info as P0351



Solutions:
- If damage, repair ignition coil circuit
- Replaced ignition coil
- Replaced PCM or ECM

P0351 Ignition Coil (A) Cyl.1 Prim./Sec. Circ Malfunction 16735 is the vehicle missing if it isnt reset code if it comes back change plugs and wires

Wiggle the connectors on the PCM during those four or five minutes...
I'm going to try the hose clamp fix myself. I have been struggling with stalling for about a month now. As a matter of fact, my PCM looks just like the one with the hose clamp. Connector C1 (black) missing the locking tab. I have tried the screw repair and zip ties. Zip ties worked for about a week and then I had a hiccup followed two days later by a full blown stall. Now it's stalling about 4 to 6 times in a one way trip to work (11 miles).
I was able to procure a clamp tonight and got it installed. When I go home we'll see. I was throwing a P0351 code with a code 43. This is an aggravating fault to be sure. I am an aircraft electrician by trade so and thanks to the volumes of people who have had this problem I have been able to do some really good fault isolation.
It exists either in the C1 connector for me or the PCM. Initially I changed the TPS and then found found C1 ready to fall off the PCM (Thus the zip ties).
Later I found that even though zip tied wiggling the harness could duplicate the fault. So another zip tie around the harness to pull tension on the connector. The fault returned. I also took a rubber mallet to the computer while the engine is running and duplicated the fault as well.
At this point I'll try the hose clamp and see how that works out. Either I don't have a good connection on C1 or the male pin 7 in the computer is a problem. Since I have an obvious defect in the locking tab on the C1 connector I'm swaying towards that. I want to talk a little system knowledge here courtesy of a guy who posted on CNet.
1. P0351 is a coil code. However:
a. The coil receives a signal from the PCM connector C1 Pin 7 to "fire".
b. There are only two wires at the coil, signal wire from the PCM pin 7 and a ground wire.
c. In order for the PCM to throw code P0351 the PCM had to fail to send the proper fire signal. Of course this assumes that you have a known good coil, clean ground and no breaks in your wiring.

2. A multimeter checks continuity not integrity. The average 18 gauge wire has 22 individual copper conductors(wires) inside the insulation. You can have 21 broken strands and still read full continuity through that single strand of wire. But that single strand of wire will not be able to handle the signal being sent to the coil (load). A load light will always check integrity AND continuity. A weak light means not enough current going through the wire and a strong light means good wire integrity.
3. So with this said, In order for P0351 to set, the computer has to give an erroneous signal to fire. Pin 7 is an OUTPUT. Now is this caused by a bad computer? Possible. A bad connection? More likely.

Let's face it computers will fail, but in my 22 years of electrical experience bad/loose/dirty connection points are the weakest link. A cold solder joint on the PC board in the computer? Yes, however this will generally show up shortly after the vehicle rolls off the assmbly line. Not 13 years later!
As for the "screw" fix. I read a post from an engineer who scraped all the resin out of the PCM to see what was on the board. The long screws go to a NYLON nut on the board. But does not come near the current path of the PC board.