99 sonata 2.4l stalling problem

After thinking about this it's a stumble or hesitation on the low end. more than a stallaing problem. sorry was using my neighbor's words instead of mine.

carl

I'm surprised unplugging the MAP sensor didn't trigger a code, but that's not important. The MAP sensor isn't the problem. It's sole function on this vehicle is to detect EGR operation.

There's a remote possibility that the stumble is an issue that will be solved by an ECM reprogramming. According to TSB 03-36-019, the reprogram will address "infrequent minor engine hesitation after an initial cold start (typically the first start in the morning)." The words that make me think this may not solve your neighbor's problem are "infrequent" and "minor."

I doubt there's any issue that would require ECM replacement. This is very, very rare on Hyundai. If I had to guess, I'd suspect a faulty air flow sensor or an air leak between the air flow sensor and throttle body.

thanks hyundaitech , I will do the test on the air flow and even borrow one to test on it monday or tuesday. The only problem with the ecu is that there is no code by unplugging it on a 2 and even 3 trip detection. There is a definate difference with it plugged in and not plugged in until it gets to normal operating temp. I used to replace lots of caps in the old mitshibishi ecu's that caused erattic problems and thought this might be the case of these but since it's so hard to get out I would check with you before I tell my neighbor that it is going to involve a lot. I did pop the cover and check the timing marks and all is in alignment just because he had a belt put in a while back. When it's cold (40 or so) it stumbles worse but after a lengthy warmup it's noticable but not to bad. Another thing i noticed was that if you did a restart after 5 minutes or so it would stumble for about only 15 to 20 seconds or so and then would be pretty good but cold is another matter. Thanks again and if you think of anything else please let us know.

Carl

The things you post seem to point at the reprogramming. You might ask the dealer to do that for you. It may even be covered by your 8/80 emissions warranty on the ECM.