Just a trend I've been noticing recently with people who are having problems with cordia's.
I've noticed alot of people just randomly replacing parts and hoping for the best. This is a very expensive way of diagnosing your problems, there is usually a logical way to narrow down problems on EFI cordia's and alot of people are just taking a guess, replacing something and hoping that it works.
So, here are a few tips:
1. Check ECU error codes
There is some information on how to do this floating around somewhere. If it reports a sensor problem check the plug and wiring for that sensor and test the sensor if possible... Then find a replacement! If there is no error code assume the sensor is ok (until you've exhausted all other possibilities)
Here is a thread from the FAQ section on how to check for error codes:
http://www.cordiapower.com/forum/viewtopic.php?t=1749
2. Check engine compression
Problems with smoke, rough running etc. can be caused by cracked pistons, cracked head, blown head gasket etc.etc. A compression test is usually the first thing you do (aside from easy-to-do checks), it's a good thing to be able to rule out, since if you have a compression related problem no amount of replacing stuff and servicing will help you there.
A compression tester will cost around $30 or so, I recommend one with the flexible rubber hose on it with a screw fitting, not the ones that just slot into the spark plug holes because they won't work on all engines. They're a good thing to have handy, and if i'm looking at a car to buy, I usually take it with me + some basic tools to do a comp test, if the car's motor is farked, I won't buy it.
Here is a basic guide on doing a compression test I have written:
http://www.cordiapower.com/forum/viewtopic.php?t=11649
3. Tackle problems one at a time
If an ECU is reporting a problem with the AFM, don't replace anything else until you've fixed this problem!
4. No Spark
Very easy to diagnose, if you're not getting spark check if the tacho is bouncing when you crank it. If it bounces, then look at the dizzy, leads, ignition coil, ign coil wiring. If it doesn't bounce 9 times out of 10 it will be the E101 they have a habit of dying - alot of people carry a spare in the glovebox!!!!, otherwise it can also be the distributor signal wire (or dizzy itself), or a snapped timing belt
5. No fuel
To check remove the fuel return line (the one on the passenger side) and see if you get fuel pissing out when you crank motor (careful!). If there is no fuel, usually a dead fuel pump, kink in fuel lines, blocked fuel filter or wiring to fuel pump
6. Running rough
Check ecu error codes
Set the TPS (
http://www.cordiapower.com/forum/viewtopic.php?t=2187)
Check vacuum advance
Check vacuum lines are routed correctly
Check spark plugs and leads if down a cylinder
Check /replace dizzy cap / rotor button
Check ignition timing with a timing light
Check intercooler piping for leaks
etc.
I hope this helps, I might write up a more detailed diagnosing guide, but the above is usually what I do when I'm having engine problems! It's by no means definitive but it's a good starting point.
The cordia 'mega thread' also has some good info you may find useful.
http://www.cordiapower.com/forum/viewtopic.php?t=7343