My fathers 1990 240 starts up in the morning with a very bad stumble/ hesiation. It will start with no problem but once running it shakes. If you push the gas pedal down and rev the motor for about ten seconds the hesiation and stumble goes away and it lets out smoke out the tailpipe. I am thinking there is a rich condition which goes away after a few seconds of running. This only happens in the morning. If you are using the car durning the day, it will not do this no mater how many time you turn it off and on. I have changed the fuel injectors, o2 and maf. I am thinking the cold start valve is leaking by and causing this issue over night. The cost for this valve is over $200. Is there a way to seal the fuel rail after I remove the injector? Could I use a new 1975-1984 cold start injector as a plug and not connect the wiring? Those valves are less than $30 new? He has the newer ecm installed in the car now.