Help. I have an 02 mitsubishi eclipse gt, v6, 3.0 liter, 24 valves, automatic  tranny. I just got this car back from my daughter who decided she no longer wanted because it was getting too expensive to maintain.

Car shakes under load but no check engine light. I took to mechanic and his expensive code reader indicated a cylinder 3 misfire. He had the car for a few days supposedly diagnosing but he indicated problem was intermittent. He changed distributor cap and said it seemed to be running alright but could not be sure. He told me my engine mount were shot. All this cost me $200 but fixed nothing.

I had tires balanced. I changed motor mounts which were shot. And today I spent about 6 hours and another $100 for parts. I removed the intake plenum (yeah, great fun) to be able to access the 1,3, and 5 cylinders. I changed all the spark plugs with NGK Iridium though all the old plugs looked good and I replaced all the spark plug wires with high quality ones.  

Issue is not resolved. Still no check engine light though. Anybody have any suggestions, other than get rid of the car?

Have you tried an Mitsubishi forum for the specific model?
I have found almost every make and model vehicle has a site forum dedicated to them.
It might be a know issue, kinda like the petc0ck is here.

Shaking under load... I would have put a OBD II tester on it, if no faults.... think tranny, or if its a front wheel drive, think about the drive knuckles...sorry can't remember the true name for those.

Thanks Justin and Old_Rider. I forgot to mention I actually had the tranny checked by a tranny shop and they told me the tranny was fine. They are actually the ones that put the scanner on it and diagnosed the cylinder 3 misfire and he did not charge me anything. The scanner did not indicate a fuel delivery issue. I forget exactly what it said but I believe it implied a spark issue. I also had the injectors cleaned by shop prior to seeing the tranny guy.

The car idles great. While stationary you can rev it and it sounds great. But drive it in a straight line not pulling anything and at around 2k rpm it starts to shake. It does seem to be intermittent as last night on the first few minutes of my test drive I pushed it hard and it ran great but then on the way back to the house it started acting up again.

Not likely to be suspension parts, but I will take a closer look just to make sure. Right now I suspect possible faulty distributor and possible faulty ECU. Do not know why check engine light does not come on and my cheapie scanner cannot pick up any fault codes so I am sure the the check engine light bulb is functional.

I forgot to mention I did find a Mitsu forum but no help so far. I am thinking of calling Mitsu dealer to ask how much for a diagnosis.

I listened to a Click and Clack the Tappet Brothers episode where a lady had a misfire in her car.....and they suspected a broken motor mount.  They had a car in their shop that had a misfire under acceleration and they found the engine would move so much that it would pull on the wiring harness and pull the wire connectors apart....and the connectors would touch again when the force on the engine was released.

If you have the motor mounts repaired and this miss is still there....then I guess it is not the motor mounts.  

Stew, Dave, thanks again. Yeah what Dave wrote was interesting. I will have to make sure the new mounts are working properly and also make sure the wires have enough slack to accommodate at least some engine movement.

Thanks Justin. I know the plug wires are good now because I just changed them. However, I will check them to make sure they have enough slack to accommodate any engine movement.

I actually spoke with a Mitsu service person today and he indicated they just recently had an 03 in there with the same problem and it turned out to be the distributor. I may just bite the bullet and purchase a new distributor if I cannot get this problem to go away.

Thanks Justin. I'm glad you clarified. I will take a look at that. I sure hope that is not it though.