[paul56chevy]

2001 hyundia sonata 2.4 4cyl. Replaced leaking head gasket. Car was running smooth before repair. But when restarted runs rough. Found cylinders 1&3 not firing properly. Check &have spark to cylinders.getting fuel, plugs are wet but exhaust manifold for those 2 cylinders are cold. Check compression .good on all 4cylinders.any help would be grately appriecated.

[TxGreaseMonkey]

. Check for codes.

. Remove and reinstall the plugs and COPs going to cylinders 1 and 3. Lightly coat the porcelein portion of the plug and terminal with dielectric grease. Do the same to the coil spring. Try and center the coil's spring directly over the plug. If the problem persists, you may need to replace coils 1 and 3. Be sure to use the same plugs that originally came with the car--check the gap.

. Check/replace wiring.

[CaptainRich]

Double check your firing order and spark plug gap.
Those aren't paired cylinders so it's likely something within the secondary ignition.
When you checked for and found spark, exactly how did you go about testing?

[paul56chevy]

This one uses a wastespark system.1 coil for cylinders 1&2 one for cylinders 3&4. coils mounted over cylinders 2 & 4. with wires to 1 & 3.swapped positions & no change. So plenty of spark injectors are working to, but not at right times.no change to engine when unplugging except not soaking plugs/cylinders with gas. Also no codes come up at all, unless I create them. Unplugging injectors or camshaft sensor.something should have as rough as it sounds. Also job took 2 weeks to finish, busy work schedule. Battery unhooked whole time. Could that have affected pcm that much.only thing I ever did different on newer cars.

[Stratmando]

Many bikes I have seen, have 1 coil for 2 cylinders, many I see are a coil for 1 and 3, and another coil for 2 and 4.
I would verify each cylinders number/location and the cylinder each coil fires.

[aldo 1]

You most likely simply need to switch the plug wires to the opposite coils. It is possible to reverse them, and not realize it! This is for anyone who may have this problem to consider.