Hard starting and intake misfires when cold

[Meridivs]

We have a ’97 Dodge RAM B2500 Van with the 3.9L V6 Magnum engine.

It has always started rather hard (2-3 keys to get it running).

Thought the replacing the IAC valve, spark plugs, ignition coil, dist. cap, rotor and wires would make it run better if anything.

After this it started to misfire in the intake (Throttle Body) when the engine is cold. After a few minutes everything is back to normal.

Any idea on what would cause this engine to misfire right after it starts?

Topic

[dan]

almost sounds like a timing issue…

here is this.
http://www.ericthecarguy.com/faq/solving-automotive-performance-issues

and this
http://www.ericthecarguy.com/faq/solving-automotive-idle-problems

[Bill]

It sounds to me like it’s either not getting fuel or it has a lean mixture when cold. This would cause a lean backfire in the intake manifold. I would check the fuel pressure when starting cold to see if the pressure is within spec and especially how quickly the pressure builds. (should be almost instant). If the fuel delivery is ok you need to scan for fault codes and read coolant and ambient air sensor data. Both sensors should read around the air temp outside (after sitting idle for 8 hours or more) They should also read around the same temps of each other.

If it has an external fuel filter if might be a good idea to replace it.

Fuel pressure should be 44 to 54 psi with the engine off. You may need a scan tool to activate the fuel pump.

[Author]

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