MY 1990 TOYOTA CAMRY DX (2.0L 4CYL AUTOMATIC) IS HAVING AN ISSUE THAT NO ONE CAN SEEM TO DIAGNOSE, FIGURE OUT THE CAUSE, OR FIND A SOLUTION; I HAVE ASKED MANY OF MY MECHANIC FRIENDS, COWORKERS (I'M AN ENTRY-LEVEL TECH), AND ANYONE THAT MIGHT HAVE AN IDEA OF THE POSSIBLE ISSUE. WHAT IS GOING ON IS WHEN MY CAR IS IN DRIVE, SECOND OR LOW, THE ENGINE SOUNDS LIKE IT'S LOSING POWER, THE IDLE GOES DOWN, AS IF IT WANTS TO DIE. THE ENGINE ITSELF SHAKES, AND IS HITTING THE SIDE WALL, CAUSING A SOUND THAT MIMICS AN ENGINE KNOCK. IT IS NOT AN ENGINE KNOCK. I FOUND THAT WHEN YOU PULL UP THE PARKING BRAKE, PUT IT IN DRIVE, AND TRY TO LIGHTLY PRESS THE ACCELERATOR, IT JUST SPUTTERS AND STALLS, BUT IF YOU LET IT IDLE IN ANY GEAR, SHIFT INTO DRIVE, AND THEN PUSH THE ACCELERATOR ALL THE WAY, IT WON'T STALL. I CANNOT TEST DRIVE IT CURRENTLY, AS MY BRAKE LINE RECENTLY SNAPPED PRIOR TO FIXING ANOTHER ISSUE (TPS). I HAVE HEARD EVERYTHING FROM REPLACING THE ENGINE, FLEX PLATE, TRANS, ETC, TO SIMPLY DOING A TUNE UP, OIL CHANGE, AND REPLACE THE TRANS FLUID WITHOUT DOING A TRANS FLUSH (TO AVOID LOSING ANYTHING KEEPING THE TRANSMISSION PROPERLY SEALED. IT'S A 32 YEAR OLD CAR, TRANS FLUID IS OLD, DON'T WANNA FLUSH ANY BUILD UP THAT IS KEEPING ANY SOFT SPOTS SEALED). I HAD SOMEONE CHECK OUT THE ENGINE TO CHECK AND MAKE SURE THAT THE ENGINE ISN’T THE ISSUE, AND IT ISN’T. I WAS TOLD THERE AREN’T ANY NOTICEABLE LEAKS, WHEN THE CAR STARTS UP THE ENGINE WORKS AS IT SHOULD (THE ENGINE RUNS BETTER THAN EVER EVER SINCE I GOT IT UP AND RUNNING AGAIN), THERE IS NO IDLE ISSUES (OTHER THAN IN DRIVE, AS I EXPLAINED), TIMING DOESN’T SEEM OFF, THERE SEEMS TO BE NO ISSUES IN PARK, NEUTRAL, OR REVERSE. THIS PARTICULAR ISSUE HAS BEEN AN ONGOING PROJECT FOR AROUND 6 MONTHS, AND PRIOR TO THAT, I COULDN’T GET IT TO RUN AND DRIVE FOR ALMOST 2 YEARS. THE ORIGINAL ISSUE HAPPENED TO BE THE FUEL PUMP; GOT IT REPLACED, RAN LIKE A CHAMP. A WEEK LATER, WHATEVER IS HAPPENING NOW HAPPENED WHILE I WAS DRIVING. I COULDN’T ACCELERATE OVER 35 MPH, IT WOULD STALL, AND THAT WAS THAT. I DID A DIAGNOSIS AND CAME UP WITH DTC 51, THROTTLE POSITION SENSOR. REPLACED IT, THEN WAS HAVING IDLE SURGING, IT WASN’T ADJUSTED PROPERLY. FINALLY ADJUSTED, AND IDLE IS GREAT, BUT DID NOT FIX THE ISSUE THAT I WAS LOOKING TO FIX INITIALLY. HERE IS WHAT I HAVE REPLACED ON THE CAR SO FAR: DISTRIBUTOR CAP, FUEL PUMP, STARTER, IGNITION COIL, TPS, ALTERNATOR, BATTERY, AND FUEL FILTER.WHERE SHOULD I GO FROM HERE? COULD IT BE AS SIMPLE AS A FUSE/RELAY? ANY IDEAS ON THINGS TO TEST, CHECK, OR ANYTHING?