I'm about at the end of my rope.
Since the summer, I must've dumped nearly $700 into my car, and it's still not running right, and now that it's getting cold and miserable, and dark early, I don't feel like having it up and die on me in the middle of nowhere.
The car in question is a 1994 Buick Roadmaster, which has an LT-1 in it. There are about 145,000 miles on it.
After changing the distributor cap, it ran like a champ for most of the first part of the year, then it started to get warm.
Since roughly late June/early July, I've done (or had done) the following, all in an attempt to isolate random stalling, usually as the car comes to full operating temperature, and then would still continue to stall sporadically.
-Coolant temperature sensor.
-Thermostat (found to be sticking- also found to be one installed at the factory!).
-Throttle position sensor.
-Mass Air Flow sensor.
- Three starters because of all the re-starting I've had to do, which killed two of them.
-A battery (all the stalling did in the other one).
-Coil and ignition control module.
-The fuel pump.
So far, replacing the fuel pump has helped the most. I've been able to drive the car for nearly two hours without trouble, before that, in two hours, I'd probably have had to let it sit for at least 45 minutes and have 15-20 attempts to restart it. Now, if it stalls out, 95% of the time, it re-starts quickly, might die once or twice more, and then continue running.
Prior to the pump replacement, the stalling/restart would also produce variously, or all at once, backfiring, an odor almost like exhaust and coolant mixed with raw gasoline, the smell of straight raw gas, and restart-and-stall after one or two revolutions of the engine.
After two mechanics, a lot of searching to try and isolate what might be going on, and a bunch of other stuff, I've come to the following conclusion, as has my father, who's been a computer engineer for 40+ years:
Dad is thinking the computer might be on the way out.
1. All the problems occur about when the computer should be getting warm. Last night, driving home in cold weather, it took a very long time for problems to develop, and the car was well up to operating temperature. I had the defroster on full, and no heat to the floor. About when the computer probably started getting hot, the problems happened.
2. The difficult re-starting, as Dad described it, is either the computer not reading input from the senors correctly, or the sensors malfunctioning. Well...all the logical sensors have been replaced.
3. The backfire/flooding/strange scents that seem to result from a badly-timed engine or badly-timed electronic components point to the computer not working well.
4. The failure would tend to take a while longer in extreme heat because I'd have the air conditioner on, on days I was operating on the vents alone in warm weather, problems came much sooner.
5. Frequently, the car wouldn't start for 2-3 hours after parking. We're thinking the computer needed time to dissapate the heat.
So....does anyone think we might be on to something- or does anyone have any ideas?
The main question is- is there a way to test the computer to see if it is actually functioning right? I discovered that changing the computer, while simple from a physical R&R standpoint, is a pain because even a rebuilt needs to be programmed and such, something I didn't realize, so it looks like I might have to let a garage do it, but if it doesn't need to be done, I don't want to do it, preferring instead to fix the problem.
Any ideas appreciated.