I am attempting to fix my dads 1997 Monte Carlo with 3.1 L V6. He just beat cancer and its a farm families only car. I started having problems when radiator fans stopped. The car started overheating, gauge does not register condition. Ac/heat does not turn on fans either but wired to battery and tested motors, both okay. Not driving. This prompted a thorough investigation; I am a refrigeration AC and heat service tech so I have a service background and just begun with this car learning how to diagnose fix repair and maintain. Could not find any information without buying a manual. Covid -19 economic crisis put my family in a bind. I can purchase manual and parts next week. So i am strictly diagnosing with no scanner. I personally believe PCM failed as my intake and spark plugs very rich with gas and starting vehicle takes a few tries intermittently. Always smell too much fuel when starting. Lacked power and timing off; transmission good usually although sometimes shifts hard and it seems as all major electrical and module based sensor and imperative car functions do not work properly. Found cooling level sensor unplugged, contamination blocking sensor probe, radiator and reservoir also filled with rusty contamination. flushed, cleaned radiator replaced cooling temperature sensor that still does not register on dash, neither does cooling level sensor that i cleaned reinstalled and plugged in. Car overheating replaced thermostat and still no water flowing through engine above 195 degrees. Suspect water pump failure. Speculation by friends blown head gasket. No water when pulling spark plug, only did one so far, car still runs. No coolant/wayer in oil. Appears belt struggles, due to water pump bearings failure and seized pump/ no flow of coolant whatsoever leaving thermostat thats installed properly. All fuses okay, please help with a lesson of experience and I greatly appreciate any help and guidance.

 

In general, you'll get better responses if the problem is broken down a bit more concisely. It's a bit hard to follow all of the issues with one giant paragraph. Just a suggestion for future posts.

As I've noted in a few similar thread with people just getting started in working on modern cars, some kind of scan tool is fairly essential to working on these. Doesnt have to be a $1000 snap on, but some basic way to read sensors.

Otherwise you just end up shotgun replacing parts (or hoping someone online manages to correctly guess based on a very limited description) which just gets more expensive in the end.

That's part of the issue with having no way to read the sensors, a pcm failure ends up just being a total guess. IMO, it's pretty unlikely that it's a bad pcm although not impossible.

The big question is - is it actually rich or is ior just not burning the fuel that's in there? A dead cylinder (from a bad coil pack, ICM, wire, plug, etc) would also cause a heavy fuel smell.

If it is actually running rich, it could be a bad sensor providing false info (MAF, O2, etc) or it could even be a sticking injector.

What imperative functions aren't working right? Has this car ever run properly while theyve owned this or has this always been a basket case that could have a mountain of issues going on?

How bad did it overheat? Worried it could've been really bad if the gauge isnt working and it has no water flow. Just makes me nervous with an aluminum head / iron block engine for head warpage (which can lead to head gasket issues).

Easy to check though- do a compression test and do a cooling system pressure test. Should be able to rent both tools from an auto part store.