1999 RAM 1500 Van 3.9L
Hubby and I in an endless process replacing part after part, would like some input. Symptoms started with rough idle and stalling, and changed to different problems as we started replacing parts.
No engine codes and no check engine light at any point.
Here's what we have done:
1.Replaced the Idle Air Control,
2. Replaced the Throttle position sensor.
3. New Battery.
4. Replaced the MAP sensor.
Some symptoms improved or changed with each new part, like at one point there was bad surging and shuddering when revving the engine, that's gone now. There was very rough idle and sputtering out then stalling, that's gone now.
Now it has a really smooth low idle, no surging, no roughness to the idle. Seems to have a little more pickup on acceleration. doesn't stall in the driveway, but while driving it will just suddenly die. We start it up from cold, drive a few minutes, it dies. Still has power (lights and radio will work) but it just dies and we have to coast to the side of the road. Trying to restart, it will crank but not start again till a wait of at least 6 to10 minutes. Then it starts right up and will be fine but if we stop anywhere and turn the engine off and the engine starts to cool off it will again die when we get going again.
Some things we have checked:
Distributor seems ok, and has good spark plugs. The fuel pump is good. We checked all the wiring we could see going to and from the computer looking for nicks or breaks, seems good. Looked down in the throttle body, it looks clean, no carbon.
We have had the van since it was new in '99 so we know it's whole repair history.

Next we are thinking of trying one or both O2 sensors, maybe the ignition coil, and somebody mentioned the crankshaft sensor.

Just wanted some input, like is this one of those cases where one part goes bad and since they are all so old each one goes bad, a cascade effect? Or is it just we haven't hit on the right cause yet?
I hate to keep buying parts if they are not going to improve anything. So far each new part has shown us a difference except the TPS but no sense replacing more parts blindly.

Thanks

 

Need to find out what's missing when it dies. Leave the doghouse off for while. You can check things from the comfort of the passenger seat. (yeah, sometimes I am jealous of van drivers..... ) Easiest to check for spark. See if you are getting any right after it dies.

 

How did you check that the fuel pump is good? From reading through the forum in the past with these Van's, your symptoms possibly sound like fuel pump may be going out.

 

The crankshaft position sensor is failing.

 

^^^What alloro said^^^ Take your chances with aftermarket brands from the local parts stores or better to search and order OEM Mopar sensors

 

I had a pos O2 sensor that would act the same way

 

A couple of things I would check would be first, are there any codes stored? You can check it with the key if you don't have a reader. Turn the key on, off, on, off, on and leave it on the third time. Don't bump the starter and it will go into self check mode. Once you take care of any codes, get an old style vacuum gauge. With all the computers around now, I still use a volt/ohm meter, vacuum gauge and wooden dowel rod to start looking for a problem. A healthy engine will pull around 17 or so inches of vacuum at idle. The gauge can tell you all sorts of things if you know how to read it. What I'd look for is how it acts when the engine dies. If the reading starts dropping and then the engine stalls, I'd look at the exhaust. Your catalyst might have melted, muffler may have rusted inside or you might even have a rodent nest inside the tail pipe.

 

So sorry I was away from the thread for a while, but I have been trying all your suggestions, and lots has happened with the van in the meantime.
We assumed the fuel pump was good because we disconnected the fuel line for a minute and fuel definitely was squirting through when we started it. But hey, if problems persist, we know we could check it further.


To HeyYou: No problem with spark, good idea to check it that way though.

To Alloro and JFloors: Spot on, when we replaced the crankshaft position sensor, that dying whilst driving cleared up. BUT the next time we tried to start it in the driveway, it had gone back to horrible idle and stalling right away there in the driveway.

To ElkCon: We do have a new O2 sensor, will be putting that on next.

To OlGrouch: No codes, and no check engine light. As to vacumm checking, that's a last resort for us, neither of us has ever messed with that before. We are hoping it's not that

THE VAN IS STARTING NOW THOUGH and not stalling!

Here's what we did since I was here last: We replaced the coolant temperature sensor and it's connector, because when messing about checking things we discovered it was corroded and crumbling. Then our son said check your new idle air control that you put in, sometimes the cheaper ones will intermittently stick.... we tried starting the van with the iac not even connected and it started, connected it back up and the van would immediately stall.
Back to the parts store for the more expensive one and now the van starts, doesn't stall, and drives around the neighborhood great.
We may as well do the O2 sensor since we have it, but it looks like we MIGHT be good to go now.

We are thinking now that there were several things that were old enough to have been causing trouble. It seemed like symptoms changed with each step we took. Hopefully we got it now, thanks for all of your suggestions.

 

Vacuum checks are one of the first things I do when trouble shooting. You can get a really big gauge at the parts store. Some vacuum caps and find a port the isn't used. Fast and easy and it tells you all sorts of things about the inside of the engine when it's running.

 

OK, well we will get a gauge and head to youtube for a how-to, and see what we find. Apparently I spoke too soon when I said the van was running.
Putting the better IAC on got us running again but after a while the stalling started again.

If we don't find a vacuum problem we will put on the O2 sensor since we have one.
Another thread I found said to check relays too, especially ASD relay and fuel pump relay so we can try that.
If still no joy, could it be the computer itself?
I need to find out if the ECU for my vehicle is really specific to my vehicle, like would a similar year work if it is the same engine? I can get one pretty cheap at the junk yard but it's not so likely I find my exact year.