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Let's guess what's wrong with my car. Okay, the car is a '97 Mercury Mystique, 2.0 ltr, auto.
Friday I start it up, everything is normal. I let it warm up for a couple of minutes. I put it in reverse and the rpm's drop well below idle and it starts to idle rough like it wants to die. I pull out of my driveway and put it into drive. The same thing happens, rpm's drop well below normal idle, even before I give it gas. It stays choppy and shudders until about 1800 rpms in second gear. Then everything runs smooth again. I stop at a stop light and it gets choppy and starts to shudder. I put it in neutral and the rpms go back to normal. No choppy feeling, shuddering, nothing out of the ordinary. I turn around and go home. Check the oil, coolent, everything that can be seen without having to go get tools. All fluids are normal.

So, I don't know anything about throwing a rod. Can you do it upon startup with a good level of oil? Could it be the trans? Can there be something wrong with the trans that would not be effected at higher gears, second and above? What else could it be? I recently had the timing belt ,idler and idler pulley changed, could this also be a the cause?

Any help would be appreciated.

maybe you need to replace your cats. If you run cheap gas through it they can get clogged up and need to be replaced. This could cause some of the problems your noticing

I have seen a stall convertor do that to a car but dont know. The car idles rough under load. Could be a dirty maf. dirty IAC. Bad cats. O2 sensor. Could be a lot of things. I would start with the IAC and MAF. They are just an inspection thing.

Don't forget to check your sparkplugs too........

check your idle control valve