Greetings. I come to you from an unlikely source (hyundaiperformance.com) with a problem I, nor several mechanics, are able to solve. The car is a 1991 Maxima V6 3L w/4spd auto, and it has 300,000 Km's on the odo. The problem is this: When you start up the car (cold/warm doesnt' matter) it chokes and stumbles when you try to drive it. It idles fine, but when you drive it in any gear it jumps and hesitates. When you floor the car, the hesitation stops until the RPM's stop climbing, at which point the car resumes it's previous faulty operation. This usually lasts 5-20 min, at which point the car fixes itself and the problem dissapears until the next time you shut it off. It doesn't matter if the car has been resting 15 seconds or a few hours, after restarting it, it begins the same cycle. I have replaced and/or adjusted the following to no sucess: MAF sensor, O2 Sensor, plugs, rotor, cap, distributor (for the hall effect sensor), a few other little things aswell. I have no idea what is causing this and it is annoying me greatly. My buddies IROCZ did the same thing, and we replaced the distributor pickup module and the problem was solved. I am used to working on carburated, points ignition styled cars (such as my 3 Hyundai Pony's RWD BABY!!) so my knowledge on sensors is limited... but an engine is an engine I should be able to fix it! I have repaired computer controlled cars in the past, (mind you TBI pushrods...) but when I open the hood of this car I see more sensors then engine. Keep in mind several mechanics don't know how to fix this either...

What the HELL could it be?

 

due to the time factors involved, I'd highly suspect an ECU problem... or the engine temp sensor may be malfunctioning..

have you run an ecu diagnostic yet?

 

Check your IAC

 

what is IAC???