Ok, I will be using correct spelling for this thread since I seriously want everyone that reads this to understand as best as possible. Before I say anything, I want to thank the local DSM fans, specially the #1 fan (DSMer, duhh), for the info they have provided in the past that will allow me to write this small help article alot better.
First of all, this thread is about the quite "popular" problem with the early generation DSM engines. What's a DSM you say? Here is a quote from the DSM fan himself (to speed this up a bit):
Originally Posted by DSMer
DSM: Diamond Star Motors. They produced the 1rst generation(89-94) of Eagle Talon/Mitsubishi Eclipse/Plymouth Laser and the 2nd generation(95-99) of Eagle Talons and Mitsubishi Eclipse.
While the DSM is commonly associated with the 4G63T(2.0L DOHC@195BHP) the lower base models of DSM came with the 4G93(1.8L SOHC@93BHP) or the 4G63(2.0DOHC@135BHP).
So now we know what a DSM is, but what is crankwalk? Crankwalk, or "the walking crankshaft", happens when the crankshaft starts moving around its housing. This causes the crankshaft to, at some point or another, wear into the thrust bearing heavily. This will cause the crank to eventually move a plate that will smash into the crank angle sensor, break it, and shut the car down.
If you know how engines work (click here
if you don't and read up as much as you can), then you should know that the only movement the crankshaft should do is its rotational movement in order to move the pistons up and down inside their cylinders. Any slight movement of the crankshaft will cause the connecting rods to move, causing the pistons to move, and not just that, you know (if you know how engine works) that the engine is connected to the transmission via the flywheel and an engaged clutch. This will cause the feeling of the clutch to act odd since the engine is giving play.
So now we know what crankwalk, or "walking crankshaft", is, but what causes it? For reasons that, as Kid Rock says, "Only God knows why", the DSM plant went with off the shelf designs and engineering when producing the 2G engines in particular. Sometimes, the crankshaft themselves weren't built correctly to standard specs. On other engines, the bearings weren't the correct ones. It strongly varies. Since the crankshaft is a bit loose (only a bit, but such a thing shouldn't even be a little bit loose), it will eventually start moving around and causing play, which will lead to harsh problems that will cost alot of money if not attended to immediatly. Something that can contribute to this is using clutch kits that have a very high pedal pressure rate, which are mainly used when building the engines for some extra power.
So should you never buy a DSM because of crankwalk? Not at all, in fact, ANY car is succeptible to crankwalk. The problem is, that these 2G DSM's are the most succeptible engines to this condition, and the warranty won't cover this problem. The 1995-1997 are the ones that can strongly suffer from this problem.
How to fix it? The most recommended course of action is to just use a 1G engine in your car. The 1G DSM engines can be bought for a very reasonable prices along with everything you will need. Some custom work will be required, and some parts from the 2G engine will be required as well. You can also just give the 2G engine a tune up, but it's not going to be exactly cheap, and the 1G engines are quite beefier than the 2G ones.
Differences between the 1G and 2G engines? First off, the 1G engines are also called the 6-bolt and the 2G are called 7-bolt. This is due to the number of bolts that the flywheel requires. Second, the 1G has stronger connecting rods than the 2G. Another difference that is quite handy, the 1G engines have a larger throttle body, intake runners and intake manifold than the 2G. The last thing (to my knowledge) is that the 1Gs have an adjustable cam angle sensor and it can be used to give some more timing to the ignition (leave it to a professional or someone who knows what he/she is doing).
That's as far as I know about DSM's and their crankwalk issues. I would like to thank again our local DSM fans for having provided some of the information. I hope this clears any doubts. If I have made any mistakes or posted some wrong information, please, feel free to PM me with the correction, and I will edit it ASAP.
People to bug if more DSM information is needed: Sundown13x, DSMer, and John (I keep forgetting his S/N, but he made the Miata post).