So, my boyfriend and I have been working on this 1992 Honda Civic LX automatic...and here is what we have replaced, the ECM, the main relay, the disributor cap and wires, the head is a new rebuild, all the top end gaskets are new, all the feul injectors, timing belt, the pistons, the piston rings, bearings, water pump, oil pump...and I think that's pretty much it. And seriously, BRAND NEW!!

Now, here is our problem...cylinder 3 is not holding compression. Checked the cylinder, both spark and feul are perfect! We did a dry and wet compression test and everything pointed to the pistons...knowing that we had just redone the whole bottom end (and all fixed reputably!), we got another perfectly fine engine (nothing rebuilt, but still working) and tried the following:

-new block, new head- cylinder 3 not firing
-old block, new head- cylinder 3 not firing
-old block, old head- cylinder 3 not firing

Anyone have any idea what could be wrong?!

Anyone think that maybe something is indeed wrong with something other than the engine...maybe wiring issue, ECM, relay?!

Also, was reading a little bit about the Coolant Temperature Sensor, which sends info to ECM for fuel injector timing...could this possibly be an issue?

Any suggestions on what we could try to narrow down the problem even further....

We are totally baffled.

 

Ummmm, which is it? Cylinder 3 is not firing (spark) or not holding compression?

Compression can only be affected by 4 things really: intake valves, exhaust valves, headgasket, piston rings.

Do I have this right, with all the different head/block combinations you have listed, you're not getting any compression in cylinder 3? If this is true, it really must be a coincidence. Nothing electrical could affect compression. You're not using the same headgasket for testing all those block/head combinations are you?

If you're talking about not getting spark in cylinder 3, that's a different case. The pathway for that is battery-ecu-ignitor-coil-rotor-cap-wires-spark plugs-ground(engine itself)
Now, everything upto and including the rotor is a shared path for all 4 cylinders. From the cap on, is where spark is separated to each cylinder. If you're not getting spark in a cylinder, it would be one of those I.e. cap, wires, plugs.

 

Okay...sorry I am a little confused and frustrated myself so i apologize for that not coming across clearly.

We are using two diff. motors (head and block) for all of the above combinations...

The problem is in Cylinder 3 only.

When we start the car and lift out the wires there is no change in Cylinder 3 for ANY of the combinations. for all the rest of the cylinders when we lift the wire out the engine begins to choke.

The compression test was done with the new head and new block combo.
and there was not sufficient compression in cylinder 3.

But now that there has been two diff. motors used and the SAME problem exsists...that cylinder 3 does nothing to affect the way the engine runs...I am starting to wonder away from the fact that there is anything wrong with either the block or the head....

 

Did you test compression in all 3 engine combinations, or just use the pull the wire method?

 

We only did the compression test in the first new head new block combo, because we were baffled why it was only running on 3 cylinders. But for the rest of them we just pulledthe wire. It still doesn't make sense why the 3rd cylinder woudn't be working at all.

In the new block new head engine, once we took the block out to put in the other one that we knew was working properly, you could see clearly that the cylinder never fired, there was absolutely no wear!

 

Ok, you're problem is more likely a fuel/spark issue. Btw, just because you're getting spark, does not always mean that you can rule it out. You could visually be getting spark, but not enough to carry out the comustion process. Sounds like you have a spark or fuel problem in cylinder 3.
You're going to have to try a new cap. You'll also need to try a new wire in that cylinder or buy a new set. Maybe you know someone that has a spare set laying around. Try a new plug/plugs, or try swapping the plug in cylinder 3 to cylinder 2 and see if the problem follows. You can do this with the injector in cylinder 3 as well, to rule out the injector. If the problem does not follow the injector, then it is a problem with the wiring to that injector. Check the clip on injector no. 3 and ensure it is tight. Sometimes they may not seat all the way, or one of the wires going into the clip may have come loose a bit.

Also do a compression test!

 

The cap, wires, spark plugs, injectors...are all new. We had already tried swapping all of those things around before we bought the new cap and wires...the problem didn't follow so we ended up buying the new cap and wires...

Im definately going to check the wiring to the injector itself.

 

We did a node test and everything looked good...
As far as the wires to the injectors, anything specific I should be looking for...and how can I fix the problem if something is indeed wrong...

 

Did you perform a compression test? And new doesn't elimate something as a problem....learned that many times over. Remove the cap and inspect the four contact points. Does the one for cylinder 3 have little to no wear?