Engine turning over and firing but wont start. timing chain looks good, has new crank sensor, o2 sensors, and cat.

change plug wire --the 336 - 339 pertain to Crankshaft Position Sensor "A" Circuit Range/Performance --Crankshaft Position Sensor "A" Circuit Intermittent your no start can be caused by your problem with the sensor or its wiring as to the 430 -- thats cat converter problem which san be caused by the 141 code which is O2 Sensor Heater Circuit --you have some kind if wiring /problem with the last 4 check and look for damaged or disconnected sensors harness --then test the sensors

Have your O2 sensors checked, with an OBD2 meter, and see if they are functioning, if not replace them. O2 sensor is located in the exhaust pipe between the motor and the catalytic converter. The front O2 sensor runs the engine and the after cat converter monitors the cat converter.

seems like if it was getting fuel it would start. if it starts with fluid it should stay running if its getting fuel. also there are two different cam gears that come on these engines. if the wrong one is installed it wont start unless you unplug the cam sensor. make sure you have the right gear. if it dosnt look the same as the old one, its wrong. also check your engine vacum while cranking. if the vacum is low its a sign the timing chain is off the marks. your plugs would all be wet with fuel if it wont fire, check for this if above checks out

This code can be a pain... unfortunately P0420 means it could be several things. Depending on how old the car is...
- Check for exhaust leaks in all pipes and exhaust manifold (visual inspection, listen for that ******* noise evident of holes)
- Get an O2 sensor socket, remove the sensors and inspect. Peer inside the catalytic converter from top and bottom, look for clean horizontal honey comb pattern. Should be obvious if pieces are falling out. Look at O2 sensors for corrosion or fading of metal, they only last ~100K. Only the upstream sensor affects how the car drives though, the bottom one just measures how good the cat is doing. Either one can trip the check engine light though.
* Symptoms of driving performance may take awhile to develop, and either a bad sensor or bad cat can cause it to run rich and burn excess fuel. Running long times with a bad upstream sensor can lead to damage on the cat, so do the cheap O2 sensor replacement first.
[My 1998 civic had the light on since I got it in May, finally performance and fuel economy started dropping. Before buying an O2 sensor or new cat, I visually inspected everything and finally took the sensors out to look at them and inside the cat. The cat and bottom sensor looked okay, but the top was corroded (I figured it was the top since my driving was being affected). I replaced the top O2 sensor and she runs nicely now, I expect fuel economy to return. You can clean sensors sometimes (no water), but usually its corroded so just replace it. $70 for a sensor is WAY cheaper than paying someone to replace you cat, which is a recommended change if you end up having to get a new cat anyway (don't want to ruin a new cat with a bad sensor dumping fuel in).

Replace the O2 Sensor and if that doesn't fix it your going to have to start replacing the stuff Identified by the codes. Most likely the Catalytic converter is bad and the Crank Position sensor. If the Crank Position sensor is sending faulty signals then it will cause misfires, the O2 sensor causes the motor to run rich, the Catalytic converter will become overheated if your running too rich or it is damaged or partially blocked.

The problem is electrical. Check the dist. and timing chain

check the fuses , you can have a o2 sensor fuse open, also check the wiring because o2s are close to the cats or manifoldss some time they burn and get shorted.., other thing you can do is unplug the o2s and drive it like that and see if it shuts off , if it doesn't so the problem is around that sensor...hope this help..

Timing chains on 3800 engines do not go bad. The older 3.8 1987 back did. You need to put a crank sensor on it first also check the ign. module under coil pack for green gel that may be coming out of it. Clean the all three battery cables and replace the two bolts too. My 1990 lesabre 3800 has 295000 miles on its timing chain.

when you replace crank sensor the crank sensor is going have to be reprogram or relearn before car will crank.

These trucks have a problem with the catalytic convertor blocking the exhaust causing a no start condition, the three things you need to start fuel, spark and air. Try disconnecting exhaust in front of cat.