If this post is duplicated I am sorry I couldn't find it anywhere.

Sons 626 seems to run good up to about 60mph then after 4-5 miles the rpm's start jumping and the tranny starts shifting. Seems to run pretty good at about 40mph. The check engine light was on, showed mis fire on cyl 1 so I changed the spark plug between a and 2 to try and see if the misfire would change so I would know that it was the plug. Now I get no misfire. And can't seem to get the light to come back on. I still have the same problem with the car changing in and out at about 60 mph. The tranny was rebuilt about 3000 miles ago. I am getting stumped, is it the tranny again? Also, it seems to be idled low how do I increase the idle speed. One other thing, when you crank it it squeels like a pig for about 5 seconds, mostly when cold. None of the sprays work do I just need to maybe tighten a belt? THANKS

 

The engine is running rough and needs a tune up.
This is how I would approach this with a 12 year old Mazda:
Search for vacuum leaks. Replace all rubber vacuum hoses and make sure that all nipples and passages are open.
Clean the throttle body and open the EGR ports.
Clean the EGR valve.
Replace all plugs, wires, rotor and cap (or coil pack).
Clean the MAF sensor.
Replace the air filter.
This is all regular maintenance stuff and you can do one part, then another. I bet your idle speed will correct itself. Once the engine runs smooth the transmission will shift less erratic.
The squeal comes from a belt, and yes spraying does not help. You need new drive belts. If you have V-belts the pulleys may have been polished smooth by the operation. Remove the glaze with sand paper.
If there is a belt tensioner it may need to be replaced.
Belt squealing can also come from a bad water pump or any other accessory that has a bearing going bad.

This will cost mostly time and a few bucks for the ignition parts. Get a Haynes manual for reference.

 

Tried everything mentioned and still no luck. I changed the plugs,wires,coil and cleaned teh MAF sensor and EGR valve. Still changing in and out after it warms up. Could it be the speed sensor in the tranny or would it that mess up before it gets hot also.

 

I don't know how smoothly a 2 cyl car can run? really 2 cylinders?
Is this a 2 rotor rotary engine?
I'm sorry, I have no clue with this car. Went right over my head.
Is it a 2.0 ltr 4 Cylinder engine?
Click Here for options: http://www.edmunds.com/mazda/626/2000/

 

OK Boys, settle down.
It does seem to me that "Noggin" was simply looking for some clarity.

As for the car: The 626 automatics from that era are known junk, and it has been said that rebuilding them usually doesn't help... for long.
Reputable salvage yards even refuse to sell them because the come-back rate is so high. But that's my best guess for your problem.
Strangely, Honda's/Acura's from that time have much the same issue.

 

not to mention i did some research and the ford probe and the 626 is the same car drivetrain wise and between 1993 and 2001 the 626 has a ford transmission in it. can u say jdm fail