The P1820 engine code seems a kind of powertrain problem and this problem is not costly and difficult to solve. Like the all car engines, this car engine method services particularly advanced hydraulic lifters what is known as switching roller followers for the engine P1820 code intake and finish valves. The lifters can be distorted by unfastening an internal locking pin. The fastening pin is disconnected using solenoids to modify oil compression fed into the lifter. The poor running is a symptom what is consistent with a MAP sensor failure. In addition, in some cases, a bad MAP sensor will not toss a code.