It builds upto 5 bar with no tools then when start to use the pressure starts to go down the engine revs go up but not by much but pressure keeps dropping and the starts to shake like mad ....what I noticed was whe. I was blasting the was hardly any pressure at the nozzle .....thanks for the replyDoes it build up to normal pressure when left running but no tools are being used? Are the engine revs OK and does it sound "normal"? Are there any warning lights? If OK, things to check - air inlet filter (when was it last changed), compressor oil level, valves worn, piston rings worn, solenoid valve leaky seat, unloader valve leaky seat. Does it hold air when the engine is turned off? If not, are there any obvious air leaks?