I've been dealing with the same code for 2 months (CSF Sensor No Signal / "P1337" Engine Speed (RPM) Fluctuation Sensor No Signal.), I cannot figure it out. I've also got random misfire codes as well. Although the car seems to run fine and i don't hear anything odd.

I've replaced, plugs, wires, cap rotor, ignition coil, I did a valve lash, and checked the timing 16'.

I'm also running rich, i can smell the gas a bit if i stick my nose in the tail pipe.

When i rev the engine i can hear it crescendoing with ticking, so i'm hoping i don't have a chipped/bent valve.

When i bought the car, i didn't have the upper timing valve cover. While i was driving a rock/pebble flew in there and cause my belt to skip a tooth. Although it still ran okay, i repalced the TB and retensioned it. I wonder if maybe a tooth might've cause my valves to hit? The cel for these codes came on 1-2 weeks later.

So what can it be? Any guesses? i've searched and searched.

My only guesses are maybe the icm, distributor, crank shaft position sensor or possible the VSs i read somewhere? Help meee pleaseee.

 

If you are concerned about bent valves, do a compression test or leakdown. If those test prove to be okay than procede else where. It is easy to speculate about certain mechnaical issues but eventually you'll need to rule them out to determine the problem. If you are not experienced than a local shop will gladly help(for a small fee of course)

 

Good call, i'll do a compression test to see.