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Discussion Starter · #1 ·
On mobile, sorry for errors.

The truck is a mix of a lot of different parts, but she's seen over 20k, and not really given me any issues, until now. Engine/injectors are '99 Ram Van (unknown mileage), trans is a '91 46RH with the Dakota's original tail shaft. Stock '92, 3.9 wiring harness with the extra injectors added to the loom. Vacuum lines are about three years old, all inspected, and all zip tied onto their ports. Plugs and wires are fine, stock replacement parts. O2 and cat were new 22k ago. Computer is an AutoZone reman, and is showing no codes. Truck is running shorty headers. It has had the wiring loom repair, under the main fuse block, that causes the computer to lose power.

It did have an issue with its CPS, that would make the truck not want to exceed 2000 rpms, or 70 mph. Found to be the CPS wires were too close to the header, and had gotten too warm. Replaced the sensor about 1000k ago, but then this a appeared.

Now, when the truck is dead cold, or fully warm, it runs fine. When it's just starting to get warm, about a mile from home, she coughs, kicks, and makes a sound similar to lugging a manual trans truck in to high of a gear. I was suspecting a faulty temp sensor putting the truck in closed loop before the O2 was warm, so I disconnected it to keep the truck in open loop. Besides for tanking my mileage, it just made the problem more pronounced, but it would do it for a shorter amount of time. Placing the truck in neutral and revving it hard would somewhat take care of the problem, but I cringe about doing this with cold parts. Disconnected the solenoid for the EGR seems to have helped a little, but it's only been disconnected for a day.

Mileage appears to have been falling since August, but I did have a job site change that has taken me from almost all freeway, to almost all city.

Here you can see what it's doing:
And my scary decrease in mileage (in the graph about half way down): http://www.fuelly.com/car/dodge/dakota/1992/exdelayed/367817

Any ideas would be awesome!

EDIT: Listened to the sound better on the way home tonight.
 

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Codes?
 

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EGR stuck regardless of the solenoid? Fuel pressure? wires from the CPS gotten crispy? Checked coil? Those things would be my initial thoughts.
 

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Discussion Starter · #5 ·
ToxicDoc said:
EGR stuck regardless of the solenoid? Fuel pressure? wires from the CPS gotten crispy? Checked coil? Those things would be my initial thoughts.
When the CPS was replaced recently, the wires were secured far from the exhaust. Coil is about 3000 miles old, but I have a spare I could swap it with for testing.

Haven't checked fuel pressure.

I am suspecting EGR, but what confuses me is that the truck runs fine when it's dead cold, or fully warm. I have always been under the impression that an open EGR would make idle almost impossible, especially on a cold truck. If this is the EGR, it will be the first faulty one I have run across in 24 years of driving.

It smells rich when cold, as expected, but the tailpipe is clean to the touch.
 

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maybe it's not stuck all the way open. maybe only partially. All the way open way make it run pretty bad or stall at idle
 

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Discussion Starter · #7 ·
ToxicDoc said:
maybe it's not stuck all the way open. maybe only partially. All the way open way make it run pretty bad or stall at idle
She was cold and I had some time to look at it before work. The valve held pressure, from both ports, when using the super scientific method of me blowing air through it. I could hear some extremely faint leaking when blowing from the intake side to the exhaust side. The valve itself operated freely when vacuum was applied. I cleaned it out with some carb cleaner, in both directions, blew through it again and found no sound (but it was still wet inside), and reinstalled. I reconnected the egr solenoid as well.

I'll be leaving for work soon, and will post back later.
 

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Discussion Starter · #8 ·
The old girl seemed much better. I took it on a route that I've been avoiding, since there is a steep hill at the point where she'd be stumbling. Climbed right up it with no issues. In the eight mile trip, she only coughed once, and that was at WOT and high RPMs.

Seemed like the heater worked really well too, but I don't see how that would be related.
 
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