To make a long story even longer....
Bought a 2000 civic with d16y8 motor. Drove good for first few days. then went downhill fast. Tried chasing the problem by cleaning IACV valve, and replacing plugs, wires, cap, and rotor with Auto-zone parts. Car ran same if not worse. At this time I found that the factory wiring harness had been cut so the primary 02 sensor and power steering pressure sensor were cut off harness completely.

Car revs fine at idle, but idles at 500 rpms no matter how far I turn idle screw up. CEL flashing with coded for miss fire on all cylinders and no 02 sensor. Wont hit vtec, stalls and sputter like its fighting to stay running all the way thru the rpm range. Almost feels like an old car with a bad carburetor. it backfires, smokes, barely makes it up incline, stalls if I put it in neutral, just a real nightmare to drive.

Disconnected one injector at a time and the only cylinder that didn't cause a change was cylinder one. So I did a compression test and that cylinder actually some how had the most compression Switched injectors around and still cylinder 1. Changed plugs around and still cylinder 1. Put factory wires back on and no change. All injectors have 9.1-9.2 ohms.

COMPRESSION:
1-140
2-120
3-120
4-100


Just ordered new engine harness and factory plugs wires cap and rotor. Hoping that is all it needs, but it just seems odd that car drove fine for a few days and then went downhill quick. Any idea of why the "dead" cylinder has the most compression?

 

What ecu in the car?

 

p2p

 

So there are no cel on for the o2 sensor when you bought it?

 

CEL light bulb was removed so codes were unknown for first few days until I scanned it and it had 7 codes, so I pulled cluster and found the bulb gone

 

Replace the parts you purchase, reset ecu and report back. You did get the o2 sensor right?

 

Your car runs like **** because it has low compression. Your compression numbers are below minimum spec on all cylinders (140 is nearly minimum). You can replace all the parts in the world but if you don't fix the compression issue it will still run like ****. Perform a leakdown test for further troubleshooting.

Time for a new motor or rebuild.

 

Yes i have a new 02 sensor going in with everything else this weekend. Im going to redo compression test this week also be uase i dont trust those numbers. The engine was hot when i did it and After i did each cylinder, i went to redo them and the needle on tester would jump up but fall right back down, so i dont think it is any good

 

Are you opening the throttle when doing this test?

http://www.c-speedr.com/howto/comptest/comptest.php

Good website on building ls/vtec, leakdown test, compression test, etc...etc...

 

Before you spend any more money, please perform a correct compression test, both hot and cold. Seems like you need a better tester too. Please post your results.

 

Battery tested perfect. I guess i messed test up with doing it with no throttle. Since injectors were disconnected i didnt think throttle mattered

 

The "throttle" is simply opening a valve to let air pass into the cylinders. It's not directly pumping gas into them. You want WOT and to remove spark plugs to make it easier to turn over. You also were correct to perform this test on a warm engine.

If you rented this tester, or it's cheap, the valves are prone to breaking. I had one that wouldn't hold pressure, just as you describe. The needle should stop at the highest pressure until you release the air with the valve. If you don't trust one, rent another one from another parts store and try it again. But if you were able to get readings the first time which were pretty consistent across the board, you probably have a bad motor.