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Missfire on a 7MGE Toyota Supra when cold

I just wanted to get some other opinions on this issue. Car spits and sputters when engine is cold. When engine is warm car runs fine. I believe that my cold start injector or my cold start injector time switch is bad. Any other advice.?

Here are a couple of Supra specific websites to check. They have been invaluable to me keeping my '88 Supra in good running order. I have not had your problem, but have seen posts about checking the function of the cold start injector researching other problems at the first link.

cool, ty. I will check it out. do you have a 7mge, gte, or a 2jz?

7MGE, same as yours.

My early 90’s Corolla has a cold start injector and cold start timer. But neither has failed so I have no experience fixing this problem. But if my Corolla does develop this symptom one day, I’d definitely verify both the cold start injector and its associated timer before considering something more complicated.

If those turn out to test ok, you may have a faulty fuel pump check valve which is allowing the gas to leak back into the tank and the fuel pressure to drop as the car sits for a period of time. This can be tested with a simple fuel pressure hold-time test.

@GeorgeSanJose, I currently have that problem with my '88. My current work-around, and I only need to do it in the morning, is to turn the ignition on for 2 seconds, turn off for 2 seconds, and then start normally.Works like a charm.

OP should verify the ECM’s engine coolant temp sensor is accurate too.

I have a new fuel pump and my engine is rebuilt as of a year ago.

The ECU is fairly simple, and will not double-check the sensors to determine if they are working within acceptable ranges like OBD-II cars. They will throw a code only when they cannot detect the sensor. If it is sending bad data, the ECU doesn’t know that.

The coolant temp sensor is a good one to check. This engine has two, a single terminal one for the gauge, and a two terminal one for the ECU.

My ECTS (cold start injector time switch) is possible. I haven’t run an ohm test on it yet. I believe it’s either that or the cold start injector its-self.

I’ve never worked for a Toyota dealer and won’t proclaim to be an expert on the FI system on this car.
However, the cold start valve (controlled by the thermo time switch) should only operate briefly and once the engine starts the cold start valve becomes irrelevant in a few seconds.

If you’re saying that the engine runs ragged for 30 seconds, a minute, 2 minutes, or whatever then I think there is another issue.

You might consider the possibility of a vacuum leak and that would be the first thing I would look at; with a vacuum gauge. A cold engine pulling in excess air due to a leak can certainly exhibit a rough running cold/fine when warm symptom.