I have a 2001 Ram with the 5.9L. Truck wouldn't start so I traced it down to the cap and rotor. The contact for the coil was flush with the inside of the cap. After replacing both I took if for a drive. Under hard acceleration I got a misfire. It idled and ran fine under normal driving. The plug wires are in the right order so that is not the issue.

Truck ran fine before the change except a little rough idle. I checked inside the plenum and it is clean, shocking as this truck has 105K on it. Wires and plugs were put on about 6K ago. I pulled a plug out to see what kind of shape it was in and it looked new.

I took the TB off and cleaned it and still get the misfire. I have checked for vacuum leaks and don't seem to have any that I can find. I only drive this truck 2-3K a year and can't figure out why the last cap went bad when it did. At this point I am thinking I got a bad cap or rotor. They are BWD parts. Any thoughts?

 

Did you get a chance to read about routing the plug wires a special way. I had that same thing until I put them back the right way.

 

Yes I read that but other than taking them off at the cap I didn't mess with them and it ran fine before. Not sure how because the contact was gone and I had just parked it the night before from a 150 mile round trip.

 

Maybe you have a couple wires switched. Happened to me before.....

 

Have a look at this thread.

It shows quite a few NON-leaking plenums with more mileage than yours. It's NOT a shock at all that gasket is intact. This assumes you've really checked it properly....

In the TSB (I'll spoon feed it to ya), there is an actual way to do the connections on the cap as well. It's near the end of the TSB and worth doing to rule out.


....especially b/c of something like this....


Not saying it will resolve, but at least assist in trouble-sh!tting it.

 

Just checked fuel pressure and it showed 90+ psi. Specs show 45-55psi What would be the effects of high fuel pressure?

 

90 psi I did not know these pumps could put out that much (double check your readings), sounds like your fuel psi regulater is shot, this is found on the top of the fuel pump (in the pix the one that says fuel line). It can be changed out by itself but the pump module needs to be removed from the gas tank. 24lbs injectors running @ 90 psi turns a 24lbs injector into a 32lbs injector it will be running fat.

 

The plugs could be breaking down under load, just becausr they are new means nothing

 

double checked the fuel pressure don't think the gauge I had loaned to me is accurate. I did notice I have no pressure on the gas cap when it is taken off. Plugs make sense taking into consideration the cap and rotor were put on at the same time and it went bad. Man I miss the old days when things were simple to work on!

 

does the misfire happen all the time? during regular acceleration too?

Seems like things were just fine before you replaced the cap and rotor -- I wouldn't dig too deep until you figure out the rotor and cap are ok.

IIRC when I replaced my rotor and cap on my 5.9L I also changed a simple and cheap sensor below the rotor - that came recommended from this forum - maybe a crank position sensor?? Hopefully someone else can chime in.