The car is a '93 GS300 (inline 6cyl) with 140K miles.
The car has been well maintained. The spark plugs (Denso Iridium), wires and cap/rotor were replaced a few months ago.
The car runs rough as though the EGR was always open or that a few cylinders were not running. This problem is with the car hot or cold, at idle or under load. No check engine light even though this has been going on for a week. I even put the diagnostic into blink mode but nothing stored. I put my timing gun on each wire one by one. They all fire regularly. I put a NOID light on 4 out of 6 injectors (couldnt get to two injectors under the throttle body) and the light flashes regularly. I put vacuum on the EGR valve and it opened and the engine runs just a bit more rough. i took off the EGR (not too dirty with carbon) and bench tested it, it opens and closes with my hand held pump. I did a block leak test (sniffs for exhaust in the coolant and changes color if positive) but came up negative
I disconnected and reconnected the MAF sensor several times and the engine does not change a bit (I would expect a change in regime but maybe the fundamental problem is masking it). But if the MAF was bad I would expect a check engine light I would think. Furthermore I'm not sure if the MAF is used in open loop and I have the problem even with a cold engine.
I checked the engine timing. It is at 20 BTDC with and without the diagnostic jumper installed. It should be 10BTDC with connector and 7-19BTDC (varying) without it connected. I rotated the distributor as far as possible and brought the timing to 16BTDC, still way over spec. I removed the upper timing belt cover, rotated the engine to TDC and the cams line up perfect (so belt did not skip).
What should I test. Help!