Hi Scotty & Community,
I have a '97 Dodge Grand Caravan LE with the 3.8L. It starts and runs flawlessly (when it isn't dying, read on!), and burns no oil at 165K miles. Here's the issue, that started about 2 years ago...
It randomly dies, most usually at idle (parked or moving makes no difference) or when decelerating from a few thousand RPM, though it also occasionally occurs at steady 70 MPH freeway speed. But, never when accelerating, only at steady or dropping RPM. Before dying at idle, you'll often hear the idle roughen, the tach fluctuates, and the idle RPM will drop slightly for a second or two before abruptly dying.
It has become somewhat more frequent lately, but still follows no pattern other than the above. It might happen several times during a 15 minute drive (most usually in quick succession after the first time), but then maybe not even once during a 30+ minute drive! It might idle silky smooth for 15 minutes, or die after 10 seconds! It always easily restarts immediately, without incident.
The "SERVICE ENGINE SOON" light never comes on just after it dies, but does so randomly for a few minutes and then goes out. Four different code scanners have verified at different times that there are no codes stored in memory, as does the on-board trip-odometer code display function.
Three local shops have failed to diagnose the problem. One told me the 5V power to the MAP sensor was only about 2.5V, therefore the PCM was possibly bad. I then found out this shop had a shady reputation, and upon testing it myself with a good DMM (that I've verified against a lab-grade bench DMM) I found it to be 5V with the key on and 5.2V with the engine idling. Its idle output voltage to the PCM is about 1.6V.
BTW, the second downstream O2 sensor (which it did give a code for back then) was replaced over a year ago. A guy gave me a new MAP sensor, the fuel pump is almost new and the throttle body has been cleaned, with before and after results the same. FWIW, the plugs have about 80K miles on them.
I know old rigs like this can be money pits and I don't wanna put more into it, but I'm gonna have to drive this thing a while longer. A year ago, mere days before we were gonna buy a new car, I had a severe injury with subsequent surgery and recovery that sucked up all the down payment money I'd saved, so well, here I am, at my wits' end with this problem. Any help will be GREATLY appreciated!!!! Thank you!