'90 Civic: Extremely sluggish low-end acceleration, poor fuel economy

plugged pcv can be compensated, just as you describe, but under load,
especially under heavy load, you /really/ want that thing working
properly. experiment with a hose clamp if you want to test.

 

i'm not sure the 90's do. my 89 does, but my 91 crx didn't - it just
had a single mark - and i did check! i think this is because at about
this time, the newer timing lights came out with adjustable advance
angle. just set the degrees you want on the timing light and adjust the
tdc mark accordingly. with the 4-mark system, you can use an older
style non-advance timing light.

 

Absolutely, for preventing the pumping of junk into the intake, the PCV
valve is 100% essential. At WOT is when you stand the greatest chance of
oil getting pumped into the intake even with a correctly-functioning PCV
valve. At WOT and high revs, blowby is going BOTH ways, both through the
PCV AND through the breather.

But for simple air/fuel management, it's not a big factor at any pressure
differential. Especially OBD-II cars are more than capable of compensating
for PCV problems, both leaks and restrictions.

By the way, I just tried the same thing on our '99 Tercel:

1): The hose-plug test was identical to the Integra, except that the idle
never dropped. It appears that the Tercel's engine management system is
faster than the Integra's, and responded too quickly for the idle to drop.
Idle remained the same.

2) When I pulled the hose off the intake, creating the same massive air
leak I had subjected the Integra to, again the idle did not drop, but
immediately began a surge cycle. The Tercel has no tach, but it did not
seem to rev nearly as high as the Integra, and its cycle time was about a
half-second instead of the Integra's full second. The idle settled down
immediately once the pipe was plugged with my thumb.

I discovered I could uncover fully half the exposed intake pipe before
cycling began. Slowly uncovering the pipe resulted in a steadily INCREASING
idle until surging began. Half of the intake pipe appears to be roughly
what would be admitted by the PCV valve itself at full-flow.

 

magnificent snipping, something some people, whom I will not name but whose
initials are J.B., should try ;-)

My 1991 Civic does.

The UK manual for the CRX, claimed to cover 1988-1991 but also in places
indicating it may be just for 1988, also shows four marks.

The UK manual for 1995-97 Civics shows four marks.

Sure. I believe you. A few perhaps pertinent observations:

The CRX is not identical to the Civic. (I assume you know this, but I wanted
to clarify for the original poster.) For example, on the CRX, the "ignition
timing adjusting connector" that needs to be jumpered is in the engine
compartment on the CRX. It's in the passenger footwell on my Civic.

My Chilton's manual has two drawings, covering the 1984-1991 Civic/CRX/del
Sols, showing four marks. But it also has a photo showing one mark.

The online UK manual for 1990-1994 Concertos shows five marks...

I'm betting the OP's 1990 Civic crank pulley has four timing marks.

 

it is mechanically and electrically.

it's in the passenger footwell of the 91 crx.

maybe it's a peculiarity of japanese imports vs. canadian imports?

the only difference at the end of the day is $20 - the difference
between sears' standard "fixed" timing light & their angle advance model.