My 98 DX hatch has been misfiring ever since I bought it a few months back. Me and my mechanic have gone through everything we could think of and can't seem to find why it's doing it.

Everything is stock except the exhaust which is sort-of Frankensteined. It has some aftermarket ebay header and they had removed the cat and put in a straight pipe.

CEL is always on for random misfires on all 4 cylinders.

I have tried:

-Cleaning the IACV
-Cleaning inside the distributor cap, has plenty of spark and no buildup
-Checked vacuum lines, no leaks
-4 new spark plugs
-Spark plug wires tested and good
-Both o2's in make it worse so I don't keep them plugged in at all. (Burns a lot of gas, I know. But I can't have it stalling every light.)
-Alternator tested and good

A few details:

-It only misfires while idle. Runs fine while driving at any speed, no misfires at all.
-Misfires slow down and aren't as bad if I'm idling at optimal operating temperature but will stall my car repeatedly when cold.
-I need a valve adjustment and will be getting one done soon. (Makes a metallic trickling noise under slight to moderate acceleration but not under full throttle.)

So with all that said, I don't know wtf to do next or what to look for.

 

I see no comp/leakdown test on that list....have they been done ?

 

^ agreed...do a comp test and get back with us...

Don't throw any more parts at the car until you do the test

 

No, they haven't. I have thought about doing them but never thought it would be needed. Would they really cause these misfires if it were the problem?

Okay, will do and will report back to this thread.

 

also when it misfires at idle have you done an injector pulse test to see if it's the injectors "cutting out" ALOT more should/has to be done. stress testing the ign sys with a HEI tester. but do those compression/leakdown test first as they can help pin point.