97 Aurora overheating, and running badly

[rspelljr]

Ok, first time post, I desperately need help, 
First off i have had my Aurora for about a year and a half, wife overheated the motor within a month of having it, it had a little over 200k on it, the one I dropped in had 104k. The immediate problem i am having is when i go to start it takes a minute, It turns over, sometimes cranks but immediately dies, then eventually starts and hesitates on start.  Once running it starts to take off sluggishly, then it will not go when hitting my gas pedal, sometimes i can floor it and it will spit and sputter for a second then rev up and take off slow.  It does it no matter the temperature outside, although higher humidity it does seem to do a little bit better.  When it is acting up, upon acceleration, it bogs down when pressing the pedal, when i start to take my foot off, it then increases in speed. Stopping and killing the engine for a few moments then recranking seems to help some.  
Now  it is throwing codes, 
P0300B MISSFIRE DETECTED

P0405A EXHAUST GAS RECIRCULATION CIRCUIT VOLTAGE LOW

P1441B EVAPORATIVE EMISSION SYSTEM FLOW DURING NON-PURGE

P1599D ENGINE STALL OR NEAR STALL DETECTED

P1660 MANUFACTURER CONTROLLED COMPUTER OUTPUT CIRCUIT

P0603D POWER CONTROL MODULE MEMORY RESET
 Now i have had other problems last year which forced me to run the fans constantly and remove the thermostat. So engine does not get up to normal operating temp.  Had a mechanic check it out and could not find any blockage in cooling system. It has all new hoses, new radiator new water pump, plugs, wires, thermostat(before i uninstalled) . 
Engine would not stop running well over 200 degrees no matter idling or driving at any speed.  I have a Cadillac specialist shop in town but funds are tight.  Not sure if running the engine cold has caused problems, but when acting up it will not run over 55mph.  I have experience working on cars for a long time, but I have no clue even after hours of googling and reading on this site. ANY advice would be greatly appreciated
On top of everything, my fuel mileage has dropped from a little over 20 down under 14

[Randy T.]

Welcome to the club! I also have a '97, I am on engine #3. GM and the P0300, it always has to be difficult. Have you checked your fuel pressure at the rail?

[rspelljr]

I have not checked my fuel pressure yet, wouldn't be a bad idea though.. It ran great today after i stopped to get gas, almost until i got home, gave me a taste of how it should be running, just a taste. It is so aggravating.

[sall]

A good place to start with overheating is simply changing the coolant reservoir cap. Running lean can cause overheating but I can't say I've ever heard that here with an Aurora, but could certainly cause the misfire. Does it actually overheat though? Spew coolant out the reservoir?

[Toronado3800]

Those are some codes I don't see too often. PCM reset? This is beyond me.

[Randy T.]

My '97 had a p0300, would run worse when it was raining outside, I ended up having a cracked spark plug. I am having fuel pump problems right now, hard to start, not enough fuel getting to engine at WOT, noisy pump. But it's been cold and it's still going so I am rolling with it at the moment, but I can't wait to get my car running good again, I need to spin my tires.

I think you can rent fuel pressure gauges at parts stores, or Harbor fright has a cheap one that works and breaks easy. Use once and destroy! lol

[RCA1186]

Feb 25, 2015 7:00:58 GMT -6 Randy T. said:

I think you can rent fuel pressure gauges at parts stores, or Harbor fright has a cheap one that works and breaks easy. Use once and destroy! lol

Yep I had that one too. The "disposable" fuel gauge. Had to teflon tape the threads so it wouldn't leak too.

[sall]

Feb 24, 2015 22:49:42 GMT -6 Toronado3800 said:

Those are some codes I don't see too often. PCM reset? This is beyond me.

Yeah the PCM code is suspect.

[rspelljr]

Any thoughts on the computer being bad. When it starts acting real bad I stop, kill engine, wait about 30 seconds and start it back up, seems to run alot better for a bit..

[Toronado3800]

Feb 25, 2015 11:29:17 GMT -6 rspelljr said:

Any thoughts on the computer being bad. When it starts acting real bad I stop, kill engine, wait about 30 seconds and start it back up, seems to run alot better for a bit..

I'd believe it was bad. No idea how to test it though. Wish I was more help. I hate problems with no obvious answer.

[rspelljr]

Me too, and I consider myself a decent mechanic. and ok at diagnosis, and this has me stumped. I knew I would be working on my rora when I bought her, but I Have wanted one since a teenager. I guess I will bring it to a northstar specialist. Will keep updated..

[emarkay]

Clear codes, check voltages AND grounds, then see which codes return. Could be bad PCM, but more likely not... Let us know what happens. Cold makes things hard - water, starting, patience...