My 1990 Honda civic 1.5 is driving me nutts. It idels rough and when you pull the #2 spark plug wire it does not change the idel or anything. I put a full tune up on it, it has spark on all wires, compression is great on all holes. When you get the rpm's up it smooths out and runs great. I pulled the #2 plug wire off at a high rpm and it studered a little. Checked every thing I can think of. I got 355 miles per tank before and now only get 315. Please help. Car only has 135000 miles on it.

Sounds like this one has a bad injector but that is hard to prove for the DIYer, can you disable spark and crank the engine over for a little while then pull the bad plug and a good cylinder and see if the two plugs have fuel on them and how strong is the smell of fuel for each one. This may show a bad injector. Test equipment may be the next step. What does the plug in the bad cylinder look like compared to the other one also.

The cylinder is getting gas. And all the plugs look the same. Still can't tell what the problem is.

You will need to pick up an adjustable spark tester and set it to 15 Kv and test all four plug wires (and rotor + cap). Insert spark tester, ground it, crank engine and watch for spark, may need to make it less that 15 Kv if good cylinders don't fire well also.

I've heard something about an ignition control module "ICM" or your map sensor... mine had a bad icm... was causingg a cylyndar to not fire at high rpm
... if its bad your wires will still prark just not hard enough

Did you figure out what the problem was? My Civic is doing the Same thing. I can be reached at [email protected] if you could provide any assistance. Thank you.