I have a 1992 Dodge Dakota with the 3.9liter 2wd. It has 174,000 miles on it. When the weather turns cold it starts running poorly. We are in the 30s in the morning now. If it is too cold it will refuse to start.

The truck will miss and back fire to the point where it will not accelerate. Once the engine warms up it runs fairly well. Just a miss every once in while. During the summer it runs fine.

It does use oil. 1 to 2 quarts every 3000 miles. I can see oil looking down thru the throttle body. I know it probably needs the plenum gasket replaced.

I wasn't sure if these symptoms point to this issue. I hooked up a vacuum gauge and it reads a steady 18, but as I am typing this I wonder if I should have tested it in the morning when it is cold.

Reading online cold weather issues seem to point to EGR/emissions/vacuum issues.

This is my 800 dollar truck so I hate to throw a lot of money at it. I don't mind spending 150 bucks for the plenum and doing the work, but if it is just an EGR valve. I don't mind keep putting oil in it.

How should I diagnois this issue?

Thanks.

 

Go ahead and replace the plenum gasket, That should make it run better. Go ahead an do the work that the truck needs. It will make it a dependable vehicle. Trust me, I just got my 87 dakota (rust free, 2wd, a/c etc.) for $400. I've already put $600 into it...eventually the oil will foul the plugs, which then will be more $$$, so why not just go ahead and replace it? Also check all vacum lines and replace ones that look suspicious, vacum line is really cheap.

 

I understand your point. I'm with you, but I want to pinpoint the problem better. This truck has been very reliable for me over the last 2 years, but it needs a lot of work.

I was going to replace all the vacuum lines, but they are hard plastic propritary lines. Can I replace them with good old rubber lines from the parts store?

 

Yeah, you can use the rubber ones from the store, just have them cut the appropriate length and have the right sized clamps for the ends.

And my old 92 dakota did something similar too, sounded awful upon start-up. Woke up the whole neighborhood backfiring and all. Turned out to be the ignition...I replaced the whole distributor unit, cap, rotor, plugs and wires. Never caused a problem since.

But I'd start with the plenum first, it's the most likely to cause failure down the road so just get it done with now.

 

Absolutly. Just get the right size lines and your good.

What you have almost sounds like a fuel issue to me..cept mine runs the same when it gets hot, think I may have gotten a **** O2 sensor >.<

 

I have been on Hughes site looking at the plenum repair kit. Does this work with a 92? It says 93 thru 2003.

http://www.hughesengines.com/Index/p...z&partid=26194

I have given it a tune up, but I didn't replace the whole distributer. Just cap, rotor, wires and plugs.

 

long as its a magnum motor, yes.

 

Yes that will work. Every now and then there are cheeper Ebay versions.

I would suggest replacing the coolant temp sensor since it only acts up when it is cold. There are 2 make sure you replace the correct one, see the FAQ for a picture of it.