AFTER STARTINGUP MY NISSAN 91 MAXIMA, I'VE NOTICED AFTER IT IS WARMED UP IT STARTS THE MAKE A "THUMPING NOISE" LIKE ITS MISS FIRING. I NOTICED WHEN I PUT MY HAD IN THE REAR EXHAUST U CAN FEEL FOR A COUPLE OF SEC IT GOES SMOOTH THEN IT MISSES. I DID A FULL TUNE UP BUT STILL HAVE THIS PROBLEM. I ASLO NOTICE WHEN I TOUCHED THE FUEL INJECTOR HARNESS THE ENGINE ACTS ALL CRAZY LIKE ITS NOT GETTING ANY FUEL.WHAT I RECENTLY DID WAS TOOK THE HARNESS OFF ONLY TO COME TO FIND OUT THEY WHERE CORRODED INSIDE. I CLEAN THEM TO THE THE BEST OF MY KNOWLEDGE. COULD THIS BE WHATS CAUSEING MY MAXIMA TO MAKE THAT NOISE. I ASLO FEEL THAT THE CAR SOMETIME HAS NO POWER AT ALL. P.S SORRY FOR THE LONG POST. PLEASE CAN ANYONE HELP ME?

 

you basically found the problem!!! I've heard that bad fuel injectors can cause problems like that(power loss, engine miss, etc.). so I wouldn't doubt that you might need new injectors! but take it to Nissan(high priced, YES, but I've found their diagnostics to be more accurate!) or any auto shop ASAP, before anything else goes on you!!!!