i have had this problem for a while, taken it to 3 different mechanics with out any help. i will be driving the car and check engine light comes on, the car loses power for a moment, light goes off and car again picks up. its not giving any codes. i have changed out the battery, i have changed the fuel pump and filter, still having problem. i recall one time car stalled that NO BUS came out over the odometer. can anyone help?

 

An itermintent problem will be hard to trace. the old addage holds true that it has to happen to find it. It could be as simple as an o2 sensor to a loose conection or a misfire. when they checked it did they use a code scanner or did the hook it up and do a diagnostic on the system? Most time a scanner will not pull codes from the system if the check engine light is not on.

 

from what i have been told they have used both, a code scanner and a diagnostics scan. still up in the air, not sure where to go with it now...

 

BadStrat is right, a scanner won't tell you the code if the light isn't on. Hopefully the shop can get the light to come on while they are looking at it. Technically when you have a CEL on the engine adjusts the air/fuel ratio and you run a little rich. I'd take the car in immediately after the light comes on if you can. My Accent's CEL is on all the time as I have a bad catylitic converter. But the car still runs decent regardless so I haven't fixed it yet.

 

sounds like an intermittent misfire
should be a history code still stored in the obdII system
even if the light is not on but it will have to be checked by a scanner that can pull history codes or datastream. if you datastream, it will tell you the misfire count per cylinder. check for a bad spark plug wire possibly arcing against something ground in the engine compartment.