Need troubleshooting advice, I have a 94 Dakota magnum V6 with atandrad trans, During morning warm ups after about a couple of minutes the engine rpm goes up and down and when I give the engine gas it backfires, sputters where I would have to hold the rpm at 2000-3000 for it to quit. Could anyone give me some suggestions here before I dealerize my vehicle.

Thanks,

Mark

 

It sounds like a vacuum leak start looking at all you rubber vacuum hose lines check you power brake booster.
Unplug plug one hose at a time the end of the hose at the point it attaches to the motor plug that vacuuum point at the motor the try to start it see if it runs if so you have a leak in that system or hose.

You can also try the pitch the hose close with a set of clamps pliers ect the only draw back if the hoses are dryed out ( DRY ROT ) and brittle you just mite cause a vacuum leak at that point where youpitched down on the hose.

Next option start the motor and spray carb cleaner or brake cleaner over the rubber hose ect see if the engine rises or lowwers RPM'S if so you could have a vacuum leak in that area.

When the Motor is reved up it dose not need so much intake manafold vacuum to stay running but at idle manafold vacuum is a must I think it's like 14# it neeeds at least back in the day when I use to have go fast cars.

The truck is13 years old rubber hoses go bad and rubber dry rots.

 

I've checked all the hose and they're fine, the problem I'm presuming is with an electronic part because after the engine has warmed up its disappears. I've changed the following: O2, distributor, rotor, wires, and plugs so it has to be something else.

Mark