My Elantra has been doing this for a while: While running (idle, driving slow, driving fast, doesn’t matter) the car will lose power and will not respond to the throttle. It does this a few times in a row usually and then starts running normally. When running normally it runs perfectly fine, nice smooth low idle and good acceleration.
I started by doing a basic tune up: plugs, wires, oil change, air filter. No change. I then swapped the throttle position sensor. No change. You can see the symptom on youtube here: http://www.youtube.com/watch?v=44GpBbYsEUQ
My first guess is there may be a fuel delivery problem causing the trouble. You might trying monitoring the fuel pressure to see if it is changing when the trouble happens. If the engine has single point injection that may be causing the trouble also.
That bright, glowing, little Check Engine light will probably have a lot to contribute.
Take it to a major chain auto parts store and ask them to pull your error codes. They do this for free. Write down the exact codes - e.g. “P1234” - and post them.
I’ll put the actual codes up soon (the printout is at home). There are two codes: The first is evap emissions control purge error which has been on there for about a year. The second is O2 sensor 1 bank 1 which is more recent, but did not preceded the current trouble.
I would like to fix the evap purge error just to clear it. My mechanic said he didn’t think it was worth the money to fix but if it’s mostly labor expense I’ll just do it myself. Anyone know how to fix the purge error problem? Is it a blocked filter?
I would like to finish troubleshooting before I do the O2 sensor just in case there is another problem which is just going to burn out the new O2 sensor.
Also could be related: Since before I got the car it has always had a hard time starting the first time after you fill the tank. Once started for the first time it starts fine thereafter. The only fuel filter on this model is the in tank one on the pump. Could a clogged filter be randomly overburdening the fuel pump and causing it to cut out? It would be strange that this would happen during times of minimal fuel consumption though…
The purge problem will depend on what code is set. If you live in an area that has emissions inspections you will need to get the problems fixed so the CEL light is turned off.