93 altima starts fine drives fine once it has been driven long enough for the engine to heat up maybe a 15 to 30 min trip it doesn't want to start back if shut off. sometimes it cranks and cranks other times it will try to start but won't after about 20 min or longer it will finally start. what could this be?

how did you find out it is the injector causing the problem? the injectors are wired in series on these vehicles, it is possible that another faulty injector may be causing the problem. although it may be difficult to find if this happens intermittently. A scope test may be the only way to find the problem. Does the engine light come on with a misfire code on Cylinder #1? P0301 or r u just getting a random misfire code P0300 ? a bit more info on the vehicle may also be helpful........ engine size? # of cylinders 4 or 6 ?

It sounds like the catalytic converter could possibly be almost completely plugged up not allowing the exhaust to leave the engine like it should. It just builds up in the cylinder head and when it gets too much in it built up and there's no where to go, it'll stall the engine. By letting it sit for a few minutes, it gives the exhaust time to find a way out and the car will restart.

replace coolant temp. sensor , disconnect coolant sensor plug after engine is at running temp. ,shut engine off then restart ,if engine starts fine, replace coolant sensor

There is a small relay about $2.00 under the dash that can be fixed real easy. I had the same thing on a Buick I had but I guess they all have the relay.It looks like a fine wire with a very small colored ball in center. I monkeyed around with mine for over a year before one smart guy showed me were it was and how to fix. Good luck hope this helps

Water pump. The impeller will slip on the shaft. As you said runs fine at idle, but when you run it harder the impeller doesn't spin fast enough (slips). Causing it to over heat. replaced to many for this problem. Also The pumps that have the metal impellers will be tight when cold, don't let this fool you. when they heat up they slip.

You say it started up no problems? Then it wouldn't start? What did it do when it wouldn't start? Did it turn over, did it do nothing/something?
From just what little info I have I tend to think it's a starter. It starts fine when it's cold but after the engine heats the starter to engine operating temperature the starter maybe starts to drag? not allowing it spin the engine fast enough to start it???
This is only a guess with the limited info. Hope this helped thanks, HAVE A SAFE AND PRODUCTIVE DAY!

you have intake leak.bad spark plugs and wires.your fuel pump in gas tank.

did you solve your problem?

is the fan working? if the fan isnt working it will overheat when idling, as it wont be sucking cold air through the radiator. a quick way to diagnose that your cooling system is fine is when stuck in traffic, turn your heaters onto hot, if the engine temp gauge shows that the engine is cooling down, the cooling system will be fine 9/10 times.

hope this helps.

1. I like to know how many miles on your Saab?