I have a 2003 Dakota automatic w/ 3.9 V6. The tachometer does not have a redline on it, does anyone know the redline for this engine? The reason why I ask this question is when I run the engine up to 4000 rpm, it cuts out and stumbles as if there were a rev limiter cutting in. What else would cause it to idle rough and cut off like it is doing?

 

there is an in park rev limiter to keep ding dongs like you from roddin the motor. Its not a high revvin engine, so dont!

 

What's with the " Ding Dong" thing, you don"t know me!!!!

 

Oh, I see you are young and still wet behind the ears!!!!

 

I belive the 3.9 has the same specs as the 5.2 (since they are the same engine except for that 2 cylinder difference). And IIRC my 1995 5.2 factory computer kicked in the rev limiter at 5,200 rpm. I have a performance computer on my '95 5.2, and it will let the engine turn something like 6,300. I've never hesitated to take my engine up to 5,600, but it quits producing any decent power up there, so I've never had reason to go higher.

But the factory bottom end of the engine can easily handle 6,000 rpm, the problem is with the valve springs... they can't take it. The valves will typically start to float before the bottom end of the engine is in danger (which is one big reason it quits producing power up there :P).

But with that said, if your engine is running rough and cutting out in gear rather than in park (since you didn't specify), then you should have a check engine light on cause something is wrong that is throwing the engine into "limp in" mode. Because it is not normal for it to cut out that low.

 

Thanks for the real reply. I did not think about a rev-limiter in neutral. The truck was in neutral when it felt like there was a " cut-out". It was my son's truck and I seldom drive it. He was out of town, and I was just checking to see if the injectors needed cleaning. Again, thanks so much.