Why does my car idle at a really low RPM while stopped, and start shaking?
You may have a misfire, a vacuum leak, or a clogged/faulty idle air control valve. It could be a couple other things, too, but those are the most common and first things you should explore. This is because:If you have a misfire, one of your cylinders is not working and while that may be less noticeable at higher speeds when the engine is spinning really fast and the throttle is wide open, at lower speeds the difference is more apparent.If there is no misfire (and no codes / check engine light), the problem is most likely air related. This could mean a vacuum leak from a hose or the intake manifold itself. Or, commonly, it could be that your Idle Air Control Valve is clogged or not working well. The engine monitors via sensors how much air is coming in vs engine speed and uses that to control fuel injection and ignition timing.If it's a vacuum leak, the engine is getting more air than it thinks it is and that is causing a 'lean' fuel/air ratio.If the IAC valve (and its passages around the throttle plate) are clogged up, the engine thinks it's getting more air than it really is at idle with the throttle plate closed (foot off the gas), resulting in a 'rich' fuel/air ratio.All of these scenarios will probably cause some sort of engine code and checking them should be your first step. Note that an oxygen sensor code will be indicitave of one of the above 'air' situations because it detects how rich or lean the ratio is.
Some info on 300 cid Ford slant 6?
The slant six is a Dodge/Chrysler engine. It was a good runner too. As for the 300 CID Ford engine, the bore and stroke is not fuel efficient. Now the littler Ford engines in the I6 layout, like the 240 CID were more fuel efficient. It has to do with the amount of volume of air and fuel that can burn in a given time period. To me the bottom line is that I agree that I6 engines with a 5 speed in a RWD small car would be nice, and maybe even in improvement over the FWD models on the market now. But they are longer then a V6 and therefore not a designers friend when it comes to a sleek look.