Lots of idle problems posted... and purchase advice

Newby here, but I had an RX-2 before many of you were born so maybe I get a little respect for that?  It was a blast.

I'm looking at a used 2000 Protege to replace my dying Taurus.  I'm excited to get back to the world of Mazda after years of Fords, Nissans, Buicks, and one sorry Renault.  The Protege (DX 1.6L manual) drives and looks like new but has two problems.

1. Check engine light is on.  Owner says it's code PO704 which is the clutch switch circuit.

2. Engine idles too low.  This is my conclusion... it doesn't have a tach.  My analysis is based on:
- Engine shakes at idle; giving it a little throttle smooths it out.
- By ear, it sounds like it's running slow.

Researching the idle problem on this and other Mazda forums, I've noticed there are a LOT of idle related questions - probably more than any other single problem.  Low idle, irregular idle, stalling at idle.  Obviously, idle can often be affected by many causes, but there seems to be a common theme:
- Everything worked great until recently
- Engine runs fine, but idle is poor.  Some people mention this occurs when they push in the clutch, or when they're stopped at a light, or when they put it in drive.
- This problem is often intermittent.

I've heard these suggested causes:

MAF Sensor bad
MAP Sensor bad
Idle Control Valve bad
Dirty EGR Valve
Bad O2 Sensor
Jumped timing belt
Dirty PCV Valve
Bad clutch switch

So I guess my questions for the experts out there is, do these cars have an unusually high number of idle problems?  Are these all reasonable causes for poor idle?

Now for the advice part.  2000 DX 5-speed 1.6L AC, CD Player.  Drives and looks great.  Has the above problems.  He's asking $3500, I'm thinking $3000 and immediately fixing the problems.  Too much?

Thanks.

well i havent tried any of thes for my idle problem but i will this weekend and post how it goes mine a 00 lx 1.6 auto and it does this all the time, it even dies sometimes when braking too hard.

Generally idle problems can usually be attributed to the idle air passages getting clogged with oil residue etc. The idle air control valve just opens up an air port to bump the idle up when a load is sensed. There is normally an air bypass screw to adjust the base idle. The base idle is adjusted by bypassing the PCM and adjusting the idle. Typically 700-800 rpm base idle. Some require 1000 rpm to idle smoothly but if you set it at 1000 and let the PCM take control it will idle at 800 or so. The clutch switch code would cause a low idle with the clutch in as it is a load and the PCM needs to know it is engaged in order to bump the idle up via the IAC. Probably just the pedal switch but i have seen bad PCM's. A broken or worn/sagging engine/trans mount can cause poor idle quality as well.

I had two 94 Proteges that did the same thing. However, even Honda was having this problem at the time. It seems that the smaller the engine the more prone it is to happen. Auto transmissions will show it the most because you are on Drive with your break on. On manual trannys, you stop and leave the car in neutral, thereby, leaving the engine to tranny connection interrupted. Both my Protys trembled horribly but never shut off or stalled or anything. If it's a bad stall where the car acts as if it wants to shut off or does shut off, I can see a fix somehwhere. If it's a constant tremble with the car running fine, you will have difficulty fixing the problem. You may never fix it. Changing the mounts will, usually, do NOTHING to fix the problem.

Actually Mazda addressed the problem with modified mounts on early models ( softer). They can only be purchased from Mazda however. There is a huge TSB on the problem.

Hey Hixx,  how can I get a copy of that TSB.  I had complained about this issue, just a little annoyance really, to my dealer.  I even mentioned the mounts numerous times.  Tune ups tend to smooth it out some, but it never goes away.  They claimed they had no knowledge of anyone else ever mentioning this issue.  I believe there is skullduggery afoot!!!!

Bought the Protege after talking the seller down to $1800.
I've done the following:
Changed oil & filter
Changed air filter (old one was filthy)
Changed plugs (old ones were burnt, gap about .060)
Ordered a replacement intake boot (old one has broken vacuum connector)
Took apart and reassembled the clutch switch
Reset the computer by disconnecting the batt (CEL is gone... hopefully will stay away)
Pulled and am currently inspecting the MAF sensor
I might tear into the EGR tomorrow
 
Has these problems:
- Low/rough idle
- Thunk in rear end going over a speed bump
- Rattle/buzz from engine/tranny at highway speed when on the gas (goes away if I lift)
- Maybe a CV joint making noise, not sure yet
 
The last one has me a little worried.  All the heat shields seem tight, and exhaust hangers look good.
Any suggestions on the problems would be appreciated

Idle problems appear to be gone.  In case anyone else has the same (intermittent low/rough idle on MT DX), here's what I think made the difference:
- Cleaned the EGR valve
- Cleaned the MAF sensor (with electrical circuit cleaner)
- Replaced the air intake tube/boot (vacuum port to the crankcase was broken)