Hi everyone!
I've been experiencing something really weird with my 1995 Protege 1.5L MT(5-speed) lately. If anyone has any ideas or suggestions, i'd like to hear them.

I guess i'll start from the beginning:

About three weeks ago a CEL on my Protege came on with absolutely no symptoms. The car ran just fine. Went to Autozone to have the codes pulled. Came up with code P0335 Crankshaft Position Sensor ”A” Circuit Malfunction.
Before rushing to buy a new crank sensor, i referred to my repair manual to see if there was any way to test the old part somehow. And indeed there was......you test the A and B connectors with Ohmmeter, and anything between 500-600 Ohms is normal. My old crank sensor tested just fine. I also adjusted the air gap, but the CEL still came on with the car running just fine.

Just kept on driving the car when one day the CEL started blinking with the car running just fine. Had the codes pulled again. In addition to P0335, it also came up with P0300 Single/or random misfire. Erased the codes and to this day haven't seen a blinking CEL again.

I then bought a new Crank sensor, just in case. But the CEL came back soon after with the car running just fine again. Went back to Autozone to have the codes pulled. And again it gave me that P0335.
I was really puzzled at that point, and while passing O'reillys one day, i decided to check the CEL there. And the funny thing was that their OBD-II reader gave me a new code - P2422 Evaporative Emission (EVAP) System Vent Shut Valve Closed. The crank sensor code wasn't showing up with that scan, just that one P2422.

On my way home from O'reillys, i decided to go by Advance Auto Parts, and see what their code reader says. Their's gave me that old P0335 again, but no P2422.

At that point i believed that it must have been that Purge Valve and not the crank sensor. I thought that maybe O'reillys code reader was more compatible with my car, or something.
Being pretty sure that i had finally found what was wrong, i decided to buy a new purge valve. I paid good money for it cause it's a Mazda Dealer part only.

A week later the part arrived, i installed it, erased the codes and started the car. About 10 seconds later the CEL was on again with the car running just fine. Boy, was i stunned at that point.....LOL.

Anyway, i just kept on driving until while passing O'reillys again, i decided to borrow their code reader again. And this time it came up with three new codes with the car STILL running just FINE:

P0730 - INCORRECT GEAR RATIO
P0715 - INPUT/TURBINE SPEED SENSOR
P0722 - OUTPUT SPEED SENSOR CIRCUIT NO SIGNAL

Now i'm really puzzled. Mine has a manual transmission, can these codes really be relevant to me? All these three codes seem to indicate one problem - a faulty Vehicle Speed Sensor, you know, the one that connects to a transmission. Does anyone know where that speed sensor is on a manual transmission, cause i looked and couldn't see anything like that connected to my gearbox? There's just one thing that connects to the gearbox, and that's a backing up light sensor/switch. I even went to O'reillys, Autozone, and AAP, and no one had that part for my car. It wasn't even showing up on their computers. All that makes me think that my gearbox doesn't even have that Input/Output Speed Sensor thingy. Am i wrong? Could it just be a faulty PCM maybe?
Anyone have any ideas as to what's going on?

 

This may explain part of your nightmare.
Go to http://www.obdii.com/connector.html
Your car is a "transition vintage" where the compliance with the OBDII standard was tenuous and Mazda Proteges of your vintage are listed as not fully compliant.
You may have to get the diagnostics done by a Mazda dealership to get any OBD compatibility issues straightened out.

I have a '99 Protege 1.8L DX (Canadian variant of the SE). I know from experience that a "random misfire" event can throw the PCM into a psychotic episode.
Check your ignition system well. Sometimes just taking the two connectors of the coil packs, cleaning them up with contact cleaner and putting them back on and removing them a few times to burnish the contacts does the trick. The coil towers and high tension harness should be clean and in good shape too. The odd way Mazda detects misfire (inferred by the waveform on the coil primary) means that it can be tricked into thinking the car is misfiring whereas the reality is that while there's something amiss with the ignition, it's not degrading the spark sufficiently to affect the engine performance.
Hope this helps get you out of the twilight zone.

 

Take a look at the PCM. I have seen a few that had gotten wet from spillage of soda/coffee. They threw odd codes.

 

Thanks for the reply. The misfire code(blinking CEL) came up quite a bit later after the steady CEL did. I don't know about your 1.8L engine, but on Z5 the coil pack is inside the distributor, so i don't know if there is anything to clean.

 

Not much of a soda drinker, but i have spilled some coffee. And on these cars the cupholders are very close to the PCM. I think i will remove the console and have a closer look at the PCM. Although, you can see the PCM and the connector plug when you remove the ashtray, and it all looks good, no coffee or any other spills/stains on it.

 

OK I'm with you. But:
1. You haven't cleared up the OBD compatibility issue (I don't know in your case, but the specific OBD spec. detail is normally stuck on a label under the hood), futhermore the type of OBD reader used by the auto parts houses is usually too crude to be trusted in your type of case, so don't buy any more stuff yet).
2. A solid CEL is a nuisance, but a blinking CEL is something you shouldn't ignore for long because running like that can damage the cat. converter.
3. The fact that you have (a) timing sensor issues, and (b) misfire codes, suggests that the timing sensor is probably OK, but either the ECU is not generating the firing pulses as it should (seems unlikely), or the distributor subassembly is not doing its job, or you've got plug wiring/ plug issues.

I suggest you start cheap and easy: pull the plugs and check for condition and color: light grey= too lean, light tan = OK, sooty black= too rich, wet= not sparking.
Your high tension harness should be in good shape, and dressed in such a way that its not contacting the engine anywhere.
If you want, you can measure the high tension wire resistance; a good value is about 2 - 3 thousand ohms per foot, so all of your wires should measure less than 10,000 ohms.
Check the plug wells making sure there's no water or oil in there too.
If everything seems good, its most likely the distributor assembly.
In addition to the coil, the unit contains a semiconductor firing pulse generator which takes the logic level pulse from the ECU and amplifies it to a high amplitude current pulse which is applied to the coil primary winding to generate the high tension pulse.
The wiring to this is via a 7 or 8 pin connector; unplug it and give it a good cleaning with contact cleaner, then plug and unplug it a few times to ensure mating contact.
Remove the distributor cap, give it a good cleaning and look for telltale signs of arcing. While you're at it, check your engine main air duct VERY THOROUGHLY too; on all Mazdas using that corrugated ducting, the duct is prone to split in the troughs of the corrugations, its very hard to spot, so you have to pop the air filter and really move the duct around to located the split(s). The air seal is good under static conditions, but under driving conditions the split(s) open and close; when open they can admit enough air to lean the mixture off so far that the engine misfires.
This usually throws a P0171 code, but only if it leaks enough while the car is idling.
This is about all you can do on the cheap, because beyond this point, you're looking at issues like distributor/ coil/ firing pulse generators, or possibly missing teeth on your timing belt.
The most important thing though is not to ignore a flashing CEL for too long.

 

Thanks for that, oldeng! I have pretty much checked everything you listed and they all check out fine. Spark plugs have good color, wires tested below 10 000 oms, no oil or dirt in plug wells, removed distributor cap and it looked almost like new in there, main air ducts seems fine too, have also checked and cleaned all connectors to different sensors. It could very well be the coils inside the distributor, but those are not replaceable and a new distributor is too expensive to just replace without definitely knowing that is the culprit.
The blinking CEL hasn't come on ever since that one time a month ago.

The funniest thing is that all these codes, but the car runs as fine as it ever has. And why is it giving me codes for parts that my car doesn't even have, like that output/input/turbine speed sensor and wrong gear ratio stuff. If that thing was malfunctioning then the Cruise Control wouldn't work right, but mine works just fine.

Oh, and i removed the center console and checked the wiring to the PCM and all connections were clean, no coffee, etc.anywhere on them. Pulling all the plugs from the PCM made the CEL go off, but came back on soon after starting the car.

When the CEL first came on, then it would also go off at times, but not anymore.....just stays on. I should, just for fun, pop by Autozone, and see what code comes up now. Although i already know, it's probably the Crank Pos. Sensor.
And that's another thing, those yellow OBD readers that AAP and Autozones have, always give me that Crank Pos Sensor code, it's O'reillys reader, which is little different, that gives me those other codes. Although, one time, theirs also gave me the P0335 code.
If i can't get this thing fixed cheap, then i'll just drive the car as long it actually gives me a physical sign that something's wrong, and i'll take it from there based on the symptoms it's giving me.