Power unit, not firing on all cylinders?

[tout]

So recently I had the car loose 2 cylinders while it was running. We replaced the power module with a used one and it seemed to work fine.

It turns out that when the engine is nice and cold it starts up and runs fine now, but when the engine has been run for a while, stopped and then tried to restart after about 15 minutes it only runs on 2 cylinders. Same symptom of when it originally went out.

If it is alowed to sit and cool down it starts up fine. Also, if I disconnect the power module for a while, prob letting the heat soak out of it by holding it, when I reconnect it it starts up again and runs alright without having to giving it a lot of time to cool down on its own.

Could something else be causing this problem or do I just have another power module that is going out and should I just buy a new one?

Thanks,
Tout

 

[luv2rallye]

When just starting cold, hold a hair dryer/heat gun on the power transistor module to see if it fails (heat sensitive) - also do coil. It's not uncommon for these to get heat sensitive with age.

 

[tout]

I bought a brand new mitsubishi power tr unit and when I plugged it into the hot engine after just being run I had the same problem I was having trying to start with the old unit. So it only starts right when everything is cool apparently, the one time I unplugged the old unit and let it cool by itself must have been a fluke that it started ok.

What else could be causing this?

Thanks!

 

[pwayzjellyroll]

He said above also check the coil, sometimes when they get hot they can fail. So like he said when you first start the car cold hold a hair dryer/heat gun blowing on the coil pack. If it shuts down you have a faulty one. I read on here, but don't understand why that certain components the power transistor and coil pack being some, that can read ok when cold and fail when hot.

 

[tout]

Well the wierd this is that once it is running it will run even when I am pushing it and the engine is really hot. I will try swapping out coils maybe one is cracked or something?

 

[tout]

Well it thought it was was the connector on the first fuel injector on the passenger side. I believe that is for cylinder four on the 6 bolt engine.

We discovered something was wrong with that injector by testing the spark on the cables with a strobe, and when we saw that all four plugs were getting spark we determined it must be a fuel injector. We then listened to all four injectors, when I remember that one plug being a little white on the tip, we listening to that one good and it didn't seem to be ticking.

When we pulled the connector off it the engine continued to run the same meaning that cutting fuel to that cylinder made no difference, we tried a new fule injector and that worked. We looked inside the injector still in the car and saw it was all gunked up with god knows what and we cleaned it out and reconnected it. It worked for a while until it got hot and sat again.

So we ended up replacing the fuel injector itself and now it seems to pass the hot start test.