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1st Gen FTW - It's AutoMedic!
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Discussion Starter #1
I've got a 1993 Dodge Dakota 3.9 Magnum v6 (I think that's the power plant) with 235,000 miles (or there abouts) with an automatic and air.

It starts and runs fine... minor exhaust noise, but no real complaints on noise or smoke or what ever. The AC is cold and I use it constantly.

It developed a problem about a year ago, and I've just dealt with it. I parked it for a while, and now someone wants to buy it. I got it running (jumped the dead battery) and then remembered this problem. I'd like to get it fixed before I sell it...

The truck has trouble staying running once it is running. The engine can be cold or hot, under load or not, AC on or off, in gear, park, or neutral.

Most of the time, I start the truck, it runs, I drive it doing what ever I need to do, then I'll pull up to a stop sign and stop.... the engine will idle way down and just shut off (It might sputter once or twice, but not common). It will re-start just fine, and then die unless I keep my foot in it just a bit. If I keep the RPM up, it will keep running (smooth and smoke free). If I feather the pedal down slowly, I can sometimes keep it running, and sometimes only keep it running a few minutes then it dies...

Here the other day, it wouldn't keep running right after starting it after sitting a few days... just keep the idle up, and it runs just fine...


WHY!!??!?!??!?!

Nothing was adjusted or changed (including the oil) between it working, and it not working.
 

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I hit **** with sticks!
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37,749 Posts
Sticky EGR valve or bad idle air control motor would be a good place to start. Low fuel pressure could also cause idle problems.
 

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1st Gen FTW - It's AutoMedic!
Joined
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15,449 Posts
Discussion Starter #3
I had thought about fuel pressure (clogged filter), but it runs fine at higher RPM... unless the pressure regulator doesn't keep the pressure quite high enough at low RPM, and it runs a tad lean at higher RPM.

One question I have always wondered... how does a sticky EGR valve cause idle problems? It introduces too much exhaust gas into the intake to support combustion of the fresh air and fuel?

I'll go poke around at those items...
 

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TPS as well.
 

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I hit **** with sticks!
Joined
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37,749 Posts
One question I have always wondered... how does a sticky EGR valve cause idle problems? It introduces too much exhaust gas into the intake to support combustion of the fresh air and fuel?

I'll go poke around at those items...
A sticky EGR valve is similar to having a vacuum leak. When the valve is open slightly at idle, its letting exhaust gas into the intake, and is causing a vacuum leak, it basically chokes the engine out. The EGR is meant to open only under load and in closed loop operation (when warm).
 

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And EGR is composed of gas that WON'T combust. Believe it or not, it is THE solution that people have come up with to reduce nitrogen oxides (NOx) from forming during the combustion in the flame front regions where the temperature is extremely high.
 
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