97 Elantra Lazy acceleration

Hello All, new to the forum. Maybe someone can help.
 
My 97 elantra with about 100k miles has become really lazy out of the blocks in about the last 5000 miles. Sometimes it gets so bad that acceleration to 15-20 mph can take up to about 10 seconds. Once it reaches that speed acceleration is much the same as before.
 
I recently changed the plugs, plug wires, air and fuel filers, all to no avail. It almost feels as though the spark is not advancing until certain revs are reached. There are no codes.
 
Anyone have any ideas

ok, is this an automatic transmission? You might find that the transmission is not going in to 1st gear. I've actually had a vehicle this happend to... it actually didn't go into 2nd either... lol Have you replaced the transmission filter recently.? If not,, you might want to replace it.. And try putting some Trans Tune (autozone, walmart etc... ) in with the transmission fluid. I"m thinking that it could be that. But, let me know what you find out...

DO NOT put any additives into the AT fluid of a Hyundai.  Unlike other cars that use Dexron or Mercon AT fluids Hyundais (as well as Kias and Mitsubishis) use SP-III AT fluid.  It's characteristics are not the same as the more popular fluids, so things that work for other cars don't necessarily work for Hyundais, and may actually DAMAGE the transmission.  Also, when you get the transmission flushed, make sure they use SP-III and not some kind of "universal" AT fluid. 
 
All of the internal failures of Hyundai ATs I've heard of have been due to either not doing the maintenance at all, or using the wrong fluid.
 
If the transmission isn't shifting and is stuck in 3rd gear, the most likely culprit is a bad speed sensor.  There are several speed sensors on the car, including the crankshaft position sensor, the transmission input sensor, the transmission output sensor, and the wheelspeed sensor.  If there is a miscompare between these sensors, the transmission goes into "limp home" mode where it just stays in 3rd gear all the time becuase it doesn't know what gear it should be in.  If this is the case, there is nothing wrong with the inside of the tranny, just the sensors that tell it when to shift.

yeah, don't put any additives into the transmission. Might cause more problems in the future. Good call doohickie. Thanks for the info. I'm used to American Engines/Transmissions. This is my first Hyundai

Thanks for all the replies. This automatic, and though its slow to shift down, it is getting into first. This also happens if I set the stick to first.
It is due for a transmision flush and new filter, so I'll get that done, and report back. One thing I have noticed is that this mainly happens when the engine is hot, and its a fairly warm day

It's gotta be one of the sensors.... maybe MAF?  (Do the 97s have a MAF?)

Well, I wont say that was a waste of 150 bucks, but having the flush done didn't resolve the problem.
 
I've also been thinking MAF, but its expensive, if its not certain that its the problem.
 
Anyone know how to test these things?

DTC - P0102, P0103 (MAF SENSOR)