i have a 99 ram 1500 with 5.9. i dnt drive my truck much during the week and this morning around 40mph it was studdering and the check engine light started flashing then shut off. anyone have any ideas why this is occuring?

 

Sounds like a misfire. If there's any codes to read a scanner would tell you what cylinder(s) are misfiring.

I'd start with the #8 plug, and check them one by one.

 

Can you do the key trick on the 99 to read codes? If so, give that a run, and see what you get. (a selection of P03XX codes would be my guess.....)

Have you had a look at your plenum yet? Probably blown....

 

I'm thinking you can on '99, is it '98 that's weird?

 

how do you do the key trick? I replaced the plenum bout year and a half or so ago.

 

Key on-off on-off on watch the odometer.

How did you replace the plenum? Do anything with the Cat and Pre-Cat O2 sensor yet?

 

If it stutters and the CEL is flashing, not only is there a misfire, but I'm betting a plug wire (or more) is/are making contact with an exhaust manifold. When that happens, the insulation melts, causing the outer mesh sheath to make contact and thus grounds the corresponding plug & coil.

Pop the hood and check all plug wires first. Been there, done that.

 

Turn the key on, off, on, off, on. Read codes on the digital odometer.

When is the last time you change plugs/wires/cap/rotor?

 

I'm thinking clogged cat. Try unscrewing the precat o2 and see how it runs.

 

OP, listen to these guys. Before I even read the replies, I knew what to check and these guys already pointed it out.


Key dance trick is 99+ key on/off 3 times with leaving it key on at the end.