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Chris (aka- Moose)
Chris (aka- Moose), Technician
Category: Transmissions
Satisfied Customers: 44511
Experience:  16 yrs. experience with auto, manual, & CVT drivelines
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Replaced 1999 Dodge Dakota pickup 3.9 V6 engine with 5.9 V8

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Replaced 1999 Dodge Dakota pickup 3.9 V6 engine with 5.9 V8 from 2002 Dodge Dakota pickup. The auto trans from the 2002 Dakota was left attached to the 5.9 V 8 engine. A 2002 PCM was installed in the 1999 pickup as well as an injector harness as required for the V 8 engine. Also replaced the crankshaft sensor. Should the 1999 PCM be used? Should the PCM be flashed? The engine starts but runs rough. Shuts off upon acceleration on when placed in gear. The check engine light doe not come on. The 5.9 V 8 engine ran fine prior to the swap.

Welcome, I'm Chris (aka Moose), my normal schedule online is around lunch and after dinner past midnight.

You will need to install a PCM for the 5.9 engine. Your 3.9 1999 PCM thinks there are only 6 cylinders plus the crank and cam sensor readings it receives are not going to be the same from the 5.9 to the 3.9.

This is my 1st answer of what can be many. You the website and myself expect you to have a ~~~5 STAR EXCELLENT~~~ experience with my help. At the top of your screen is the rating box that you only get to use once. Please make sure to complete the mandatory rating when ready or reply and say "I am pleased with my answer". Not rating or rating 1-2 stars does not benefit you nor me in any way.

Thanks Moose.

Customer: replied 1 month ago.
Hi Moose! I installed a PCM for a 5.9 V8 during the engine swap.

What year model PCM was installed?

Does it run like there is a misfire?

What is the fuel pressure?

Customer: replied 1 month ago.
Hi Moose! The PCM model year is 1999.
Yes, the engines misfires.
The fuel pressure is 40 lbs. psi

Can you remove plug wires one by one to find the cylinder when disabled does not result in it running worse?

Fuel pressure remains 40 even when it stalls?

Will your scan tool show fuel trims?

Customer: replied 1 month ago.
Hi Moose. The engine runs worse when each plug wire is removed. The fuel pressure remain constant 40 lbs when the engine stalls. The scanner shows P0206 cylinders 6 and 7 open circuit. Another screen Fuel 1 low; fuel 2 NA.

Have you monitored the CMP and CKP sensors while running to see if they compare as well as to see if either drops out it signal. Have you done a distributor sync with your scan tool?

We have confirmed its not fuel pressure and its not one cylinder to blame more likely all and random.

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