Hi everybody. I know a guy who works on these motors and he's been right about the things that have been wrong with it, but he isn't so sure about this one because it's not common I guess. I also looked in the common monte carlo problems list and didn't see anything like what mine is doing so here you go.

Preface: I just got my lower intake gaskets replaced.
I got my gaskets fixed for 700 bucks, but now there's something else wrong with my car. It was starting to have the symptoms it has now before I took it in, so it wasn't the mechanics fault. Anyway in order these were the symptoms:


1. A couple weeks ago, my car was stalling before the engine would turn over. (I thought it was being caused by my gaskets, I don't believe that now.)


2. After I got it back from the shop, the car would start if it had been idle long enough for the engine to be room temp, but it wouldn't start if the temp was over 100. It wanted to, but wouldn't.


3. A couple days after my car is out of the shop, or today if you like, I started it up just fine, because the engine was room temp, but as I was driving it started to shut off. The rpms started going to 0 and back to 1500 then back to 0 and finally shut off entirely. I can start it back up if the engine is room temp still, but it will not stay running longer than 30 seconds. Most of the time it shuts off after a couple seconds.

Any idea? Some suggestions I've been given: starter, alternator, gas pump, clutch system, crankshaft position sensor. My car is automatic and my buddy says that rules out clutch system problems. He believes it's the gas/fuel pump and a crankshaft position sensor going bad.

 

i definetly believe the fuel pump my car sat for 5 years and the pump was bad just call a junkyard get one for 40 bucks thats what i did and its been fine the last 13k mi

 

Check the fuel pressure. The idling issue sounds like it could be a failing IAC.

 

First, have you scanned for ANY Check Engine Codes? A high end scanner can even tell you trouble codes that occurred but have not caused the Check Engine light to go off (this might be helpful).
What is the approximate temp when the car finally dies/stalls?

What it's not and why:
Not a starter - Once the car is started, the start does nothing else. But I have had a car that had dirty connections at a starter and ALL electrical (lights and all) would die while driving then come on magically. Cleaned the corroded connection, no issues.
Not the alternator - Since you did not mention having to recharge the battery, the alternator is not a factor here, it's doing it's job.
Clutch System - The auto trans does have internal clutches, but the fact you put it into park or neutral and try to restart and it won't rules out the trans (even if heat was hypothetically causing the trans to fail, in park or neutral the trans should be dis-engaged, allowing the engine to start).

What it could be (making assumptions based on description). Key elements are things that temp could interfere with the engine operating:
- MAF Sensors can do screwy things when they fail. I have not heard of one behaving like this. But simple test, next time the car stalls/dies and won't restart, get out and disconnect the MAF, restart. The car will ride on some "default" values and should run. If it does, replace it.
- Clogged cat, if no exhaust gases can get out as they should, he car will stall (can't breath). When it stalls, as soon as safely possible, get out, look under the car. If the cat is glowing/cherry red, that's your problem.
- Possible fuel pump issue. When the pump gets hot, it's failing.
- Oddball electrical problem (possibly beyond forum diagnostics).
Those are ideas off the top of my head. I tried to list them at the cheapest/easiest to test/check for to the more difficult or costly.
Good luck.
BTW - The 3100 is actually a tough little motor (the 3400 is based off it's design). I sold my '94 Grand Am this October with 215,000 miles on a never rebuilt 3100 (worst thing I ever did was head gaskets).

 

to add to the maniacs ideas, possible crank sensor getting hot and shutting down

 

The Maniac, it's a GREAT thing you mentioned why it might not me some problems and why it might be. You said it couldn't be the alternator because I didn't mention any battery problems. Well, actually there were battery problems. My buddy took a volt meter to my battery and said it barely had any juice in it. We jumpstarted it and tried to take off, but the car shut off. I looked it up and the alternator may very well be the problem.

I hadn't previously mentioned the battery, because I thought, "well it's just a dead battery, I'll get a new one, better not bother complicating this post with anything as simply as that."

However, that doesn't explain the other symptoms. My realistic guess is that I need a new alternator and something else is wrong. We'll find out. I'm going to look at it tomorrow, I haven't had any time, but finals are over, so we'll see and I'll let you guys know what's up. For now, I'm going to work under the assumption that it's just the alternator.

 

If you think it is an alternator, the parts stores can do a battery/alt test. And if that is NOT conclusive enough, take the alt off and have them bench test it. Just some piece of mind before dumping money on it.

But if the battery is NOT getting charged, that could be an indicator of a bad alternator.

 

Repairs have been made to the car. My mechanic cousin had me get another battery because the one I had was shot. In addition to that he cleaned up the cat converter, only to find that it wasn't the problem. Which is what he believed it was.

After that, him and another mechanic started checking for the solution using the list of problems provided in this thread. They started with the alternator, tested it and it did fine. The other mechanic noticed something wrong with the wires connecting the crank postion sensor to the ignition control module. Apparently one had fallen on top of my exhaust and melted. The rest had tears in the rubber. So he replaced those and rewired them so that one wouldn't fall again.

After all this, my car no longer shuts off in the middle of my driving. However, there are some remaints of symptoms. The car still gets kinda hot if it just sits still. And it still has trouble starting up when the engine is hot( not red, just hotter than 100). So far, it hasn't not started, but it stalls a bit before turning over.

But I've only had it for a couple days since the repairs were made. Maybe it just needs a coolant flush, there is still some oil in my coolant reservoir from when the intake gaskets were blown. I won't have to worry so much about heating though coming into winter.

 

One more thing, can't scan for any check engine codes, (I'll explain this the best I can) because the scanner he has to check for those needs 12 (metal prongs? receivers?) in the thing that it plugs into, and mine only has 2 showing. And the check engine light hasn't come on since the gaskets were replaced.

 

Sounds like the scan tool you have access to is NOT an ODB-II tool (sounds like it's an old tool). Unless this is a much older car, you need an ODB-II scan tool (there is only 1 data pin in the connector).

Also, glad you're primary problems have been solved. As for the temp issues, if the coolant has not been properly bled after the LIM gaskets were done, you MIGHT have an air pocket. When LIM gaskets blow, you really don't get much if any oil in the coolant (as the cooling system is pressurized and the coolant gets into the oil).

As for the starting, if it has not been done, change the plugs and wires. Plugs and wires are cheap. I recommend NGK and AC Delco plugs. Do NOT use Bosch plugs (they are junk for GM V6 engines).

Make sure the tips of the coil packs are clean (if not, use a scotch brite pad to "shine" them up). If they are corroded, you may not be getting good spark and that might be a cause.

There are many other possibilities (maybe even another damaged wire). But those are a couple things to consider.