My 2002 Hyundai Accent goes into 1 gear smoothly, jerks into 2nd and goes into 3rd gear smoothly. Then goes back down into 3rd and 2nd gears smoothly and jerks back into 1st.

have you checked the transmission fluid...does it smell ``heated``,
is the fluid red or dirty?

When the check engine light flashes it means DONT RUN IT or you will damage the engine. There are codes that your mechanic pulled from the computer, WHAT ARE THOSE CODES?

Check sprak plugs to start. Sounds like possible cylinder not firing.

Synchronization of gears is off line, some cars have that and unfortunately you would have to dismantle the gearbox to fix it.

gear change linkage worn to excess ,

Sounds like you need a clutch

hyundai accent codes p1529 and po734

It sounds like you may have 1 or more bad motor mounts. I had the same thing happen in my 93 eclipse. The rubber collapsed and the motor would just **** back and forth and make the car bounce, but 3rd on up was fine. Check to see if any of the rubber mounts have deteriorated, and replace them soon or it can cause more damage, like broken flywheel bots and bent axles. Hope this helps :)

hi fro uk this is a common problem on many cars not just hyundai and ita most common cause of synchro mesh failure on2nd and 3rd gear is believe or not a bad driving habit! it goes like this when you set off in 1st then cange up 2nd gear whilst accellerating holding gearstick? in back position then change up 3rd gear still holding gearstick! in a forward position then? when up to 4th gear we let go of gearstick?? now just by holding g/stick whilst in 2nd and 3rd the slightest pressure also brings the synchro ring into play whilst gear already selected! so inevitably the synchro ring wears away to extent that they no longer work properly so the gearbox is none synchromesh on 2nd 3rd gears and on occasions? on 5 speed box 4th gear can become a victim ? hope you understand ? just quietly observe some peoples habits with manual boxes? as for repairs?cost? this is not a difficult job to replace all synchro rings but box has to be stripped and assesed ? the cost could escalate? but if you want quick turnround? a matter of hours? a recon box with warranty? is other option ? BUT would not advise risking a 2nd hand box probably worse or same as ? whichever choice you take you can check clutch at same time if milage is high? now some good advice! personally this is not a dire problem just a niggleproblem which if you take time in changing gears you can o/come gritty gear change save money for now till it is more affordable ? if you know any old timers truck drivers ? these are the guys who will show you how to drive /change gears none synchro mesh before it was ever invented ? hope this helps daughter but practice on gears and rid of the bad driving habit so many do not realise they have will make her a better experienced!driver