I just got a new motor put in my 92 lude Si, and it had 100k on it. It ran great for a week, then started skipping a bit. For the next 3-4 weeks, it has gotten worse a bit. It only doesn't do it all of the time, but when it does it will do it for a while. It skips up to about 4k RPM's, then all 4 cylinders will start firing(1 cylinder misfires until then). If I floor it, though, all 4 will fire. It only does it under about 4k rpm's and at <.75 throttle. What could it be? I've replaced all plugs and wires, checked fuel pressure, etc. My mechanic says he can't do anything unless it throws a code or he can drive it and feel it do it, but it never does when I take it up there, and there's no code! Also, it seems to be worse when it rains; the other night it poured and my car had a cylinder misfiring all the way home from the mall, regardless of rpm or throttle pos. Any ideas? Someone on another board said it might be a bent valve that wasn't seating properly; wouldn't that make the symptoms happen all of the time?

 

Have you checked your distributor cap, rotor, and ignitor?

 

I haven't check my rotor or anything, but the mechanic said that would cause it to skip all of the time, and if the distributor had got wet, it would have dried by now. I am going to buy some feeler gauges tomorrow and check my valves; i have a write-up from preludeonline.com on how to do it. Would valves outta spec cause these symptoms only periodically? I'm thinking that it might be temp. dependent, but it does it even after the engine has got hot.

 

hmm, sounds like the problem i had, my rpms would jump then i would have backfires , and it just didn't feel right, try having your mechanic check all the ground wires, cuz that was my problem, i didn't have a ground wire attached correctly and it did the same stuff, and it was cool too cuz my tach randomly jumped from like 2 or 3 till it hit 20mph on my speedo that was annoying

 

i wish it was something like that; it doesn't do anything else but start skipping some occasionally. Nothing points to an obvious problem

 

change your cap and rotor, then check the coil...i had a bad coil and it missed and shook like hell below 2500 rpms

 

Here is something you might try: Pull off the fuel rail and check the little filters on each injector. Wouldn't hurt to clean them up, and maybe swap #1 to another cylinder and see if the problem moves with it. Might have some crud in there from the swap, ya know? just a thought...

 

In the next week I am going to check my valves myself, change the dist. cap, rotor, coil, etc.
Questions: If I check my valves w/ feeler gauges, will it also tell me if a valve is bent? and how can i check my coil myself?

 

You can do a compression test to determine if the valve is bent.

 

Adjusted my valves, but didn't really fix anything. I also noticed that I have a bit of a rough idle... a bent valve is starting to sound right. Also, could someone help me w/ the difference in a wet and dry compression test, and which would be better? Can you use compression test gauge to do a leak down test?