Hi, I have a 1988 Dodge Dakota with the 3.9L V6 and automatic transmission. I've had this truck for nearly 2 years and its been very good to me until about half way through January. Its developed a weird problem where if you start it, warm it up to where the thermostat opens, and put it in either drive or reverse the engine will stubble and die. Then when I go to restart the engine it cranks and tries to fire but won't start. When cranking it sounds like the timing is a bit off. Sometimes it gets close to starting but then the starter kicks out. It also doesn't matter if the accelerator pedal is depressed or not. You have to wait for the engine to cool down almost completely for it to restart again. The engine runs perfect when cold and when put in gear it still runs fine and can be driven too. This problem only happens when warm and where the engine rpm dips low enough for it to stall such as putting it in gear or stopping at a stop sign. It also runs a bit off when warmed up in park or neutral but still can be revved and will idle. I don't have a check engine light on either. When it first started doing it I checked the codes and got o2 sensor then it stopped saying o2 sensor and started saying coolant sensor so I replaced the coolant sensor. The other odd thing I noticed is that when it does the problem, there is a fair bit of white smoke in the throttle body. I think its just unburnt fuel. The exhaust smells rich at times but not always. Anybody have any ideas what is doing this?

 

How many miles on the engine and the truck?

 

The odometer reads 317,000 km which is about 197,000 miles. Its a high mile truck. A couple other things I'll mention are that the egr vacuum line is plugged off and has been before I've had it. I would think that rules out the egr. I also replaced the coil recently because it was leaking. I'm going to replace the o2 sensor as well. I have one vacuum leak that I know of but I don't think its the culprit. According to my Hanyes book, it's the canister purge line. One other thing is when the engine does its problem, If I floor it, the engine stops firing so would that rule out too rich of a mixture? To me this seems like a sensor issue. When this problem first started happening it was extremely cold (-40C) with even colder wind chills and lots of snow.

 

Your bigger problem is you live in a place that is TOO DAMN COLD!

 

Before you start throwing parts (and money) at it, check some things out. First off, how many miles on your timing chain. It's a bit involved but you can check the slop in your timing chain before you take the truck apart. Rotate your engine by hand with a socket and ratchet and mark the harmonic balancer. I like to get the timing mark near the indicator tab. Mark it with soap stone or similar material. Pull your distributor cap off and mark the rotor location with a marker of some sort but NOT a pencil. The graphite in a pencil will cause arcing. Slowly rotate the engine backwards slowly by hand. 2-4 degrees isn't bad. More than that, you may have a lot of slop in the timing chain. It might even have jumped a tooth.If your timing is off, the engine will never really warm up, power will be down, fuel consumption will be up and it can be hard to start.

 

I love learning stuff like this.

 

So I was doing some thinking today about my truck issues. The SMEC is connected to the air pickup for cooling. I mentioned that this winter, we had lots of snow and also high winds. If some snow blew into the air pickup, could it have gotten into the SMEC and maybe messed up something? I tried to take off the little connector pipe on the SMEC to look in it but its stuck and I don't want to break it. If my problem is timing this to me makes sense.
On checking the timing chain, it could be a problem but I don't think is my problem. My problem happens only when the engine is warmed up. I don't think that it could have jumped a tooth because I would have running issues both warm and cold. At least that's what I think. I have no idea how old the timing chain is. For all I know, it could be the original. I'm still going to check it though.
Also Saskatchewan gets pretty nasty winters ever year. This one was especially cold but most of the time they aren't much better. We usually get a few days of -35c to-40c but this year was multiple weeks of that mixed with high winds.

 

OK I've researched this and it seem worth it to check. It could be the crank sensor going bad when warm (check the wires and connectors too) or it could be loss of compression.
IDK how to test the crank sensor. It if is stuck rings I have an oil flush method I use. Thank an Aussie Geezer who I got it from if it's stuck rings and it works
Drain your oil. Remove the oil filter w/o damaging it, pour out the oil and put it back on. Put in 2 quarts of new oil and a half quart of diesel fuel. Drive it normally for a day. When I did it the first time to my Dak I drove it down a twisty two lane hwy partly in low mountains for 50 miles then turned around. Drain the oil, remove the filter. Put in new filter and new oil. If you had stuck rings it should have loosened them. You might consider using a quart of Risolone in place of a quart of the new oil at the end too. This also cleans up parts where the oil flows, apparently it helps valve seals, seal better.

 

Ok so its been a bit over a week since my last post and I've made some progress. I changed the o2 sensor because it was throwing a code at one point in time and I also changed the throttle position sensor. I was starting suspect the tps was going bad when the idle was jumping around and if I was revving the engine a bit, the rpm would randomly drop and come back up again or go higher then back to where it was. Since I've changed those too sensor my problem has changed a bit. My problem only happens on the first startup of the day. Any other time after that I start the truck, it won't do my problem. The other thing the last time I started my truck in the morning it didn't do my problem until I shut it off and tried to restart it. What the engine did do when I put it in gear is that it missed once and stayed running but not very well. When I took my foot off the brake and pressed the accelerator peddle, the engine tried to stall but caught it self and the truck moved fine. So now I'm trying to figure out what changes from sitting for a few hours to cool off where the engine is running good when warm and drives fine vs sitting over night and when warmed up it does its problem.
The other thing is this truck is a 1988 Dakota so according to my Hanyes book it doesn't have the crank position sensor and to double check I couldn't find it on the engine either.

 

I can only vouch for my 1993 Dakota with 5.2L but the crank sensor can be accessed from the passenger side of the truck. I believe I had to remove the splash guard (possibly the fender well). You should be able to see it bolted in the back of the engine next to the tranny on the passenger side of the engine. There aint a whole lot of room there. I believe the wire crossed over to the other side (driver's side) up and over the tranny to a connector that then goes to the tranny. The area the crank sensor is mounted can possibly be all gunked up with leaked oil sludge hiding its identity (look for the wires). Mine was. I had leaky valve cover gaskets (not anymore )