# 1991 SE 1.6 missing one cylinder only > can't tell which or why ??



## lou abernathy (Apr 19, 2014)

Missing on one cylinder only (can't identify which)

1991 SE w/1.6 engine......(230k miles but excellent condition, exc. miss(new)

SYMPTOMS >
- startup has no misses, but single cylinder begins missing 1-to-2 minutes later and progresses quickly to full miss (every revolution)
(suspect that startup enrichment step MIGHT provide enough fuel to get combustion (??).....but that is a GUESS 

- miss is detectible to about 3000 RPM, above that , can't tell but probably still there

- plugs are new, all appear same (no deposits)

REPAIRS / TESTS done >
- All plug wires measure (ohms) within specs
(wire to cyl 1 substituted out......no change)
( timing light shows electrical miss occasionally on #1 cyl, but nowhere near all the time)
(a possibility MIGHT be low secondary (firing) volts, but with 3 cyls good, 4th should be firing at least some of the time)

- New plugs done, twice (correct NGK)

- New distributor cap (Japan mfr)
(Rotor looks and tests fine....and bad rotor should affect all cylinders)

DIAGNOSIS ??
- Seems like MAYBE injector either clogged -or- not working electrically ?? (yes / no / what ??)

(how can i find out which cyl ??......can't tell which cyl is missing..... and advice is: don't unplug wires, like in old days, else risk ignition damage)

- Is there any way to measure injector electrical without pulling injector out ....cyls 1 & 2 injectors look blocked by throttle body, cyls 3 & 4 clear ??)

- If injector has to be removed, can the fuel rail be pulled without removing the throttle body ?? (throttle body removal looks really hard)
(TIA) Lou


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## b13er (Apr 7, 2010)

lou abernathy said:


> Missing on one cylinder only (can't identify which)
> 
> 1991 SE w/1.6 engine......(230k miles but excellent condition, exc. miss(new)
> 
> ...


You can test each injector three different ways, all without removing the injectors.

1. Put a screwdriver up to an injector and then put your ear up to the handle of the screwdriver and listen for a click noise, which is the top image (1) below.

2. Test the resistance in ohms, which is the middle image (2) below.

3. And that one I've never heard of until now where you remove the dizzy which is the bottom image (3) below.


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## b13er (Apr 7, 2010)

Also,

You should check your fuel pressure after the fuel pressure regulator. You should get 43.4 psi.

Alternative: If you can't do that, you can at least take out the bottom portion of the back seat and listen to the fuel pump. Have someone else turn the ignition switch to on (not trying to actually start the car and not just in accessory mode either: two clicks is on), and you put your ear up to where the fuel pump is. Listen for any erratic sound, it should be smooth, if it's not then it's messed up. I saw one like that on this forum.

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You should at least get a new $10 distributor cap. New wires too; my brothers Hyundae Elantra had special spark plug cables (they didn't look special), they all testet perfect ohms, but a mechanic said it didn't matter and they could still be messed up, sure enough new cables fixed it. The same scenario happened again recently to my friends Lincoln only it had normal spark plug cables. If you get cables, buy NGK's at Rockauto.com for $50, autozone.com wants $119 for them. 

----------------------------------

You can buy a spark tester (available at any autoparts store for cheap) to test the spark of each spark plug.

Alternative: WARNING you can get very shocked, don't try this at home: take out the fuel pump fuse, and then take out a sparkplug. Leave it plugged in to the wire, and hold the base of the spark plug to the engine block. Have someone try and start the car. Note how big the spark is, and then test every plug.


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## lou abernathy (Apr 19, 2014)

UPDATE > * ignition re-done....tests run* 
*Still missing* (steady single cyl miss from idle to at least 3500+ rpm, probably higher..)
- new distributor cap, rotor, all wires...... plugs are new (2nd set)
- trigger wheel inspected...very clean, blew air over wheel-notches & sensor to be sure.
- external plug-fire test shows spark on each plug....spark looks similar on all plugs
- timing light senses steady fire on all plugs (good timing light used this time)
*Problem cyl seems to be #1 >*
- Current Idle, with miss, is 750 rpm........removing wire to cyl #1 leaves idle at 750 rpm
- Wire removed from any other cyl drops idle to 500 rpm
- to check possible ignition coil weakness at cyl #1, shortest wire that would reach it was substituted (#2 wire)....
( cyl #1 is longest wire / most wire resistance)......but it still misses with shorter wire
coil has not been replaced....if anybody knows a simple high-voltage test (??)....pls reply (does fire plugs externally) 
*It's an INJECTOR problem ????*
- all injectors click loud and steady, including cyl 1 injector (using stethescope)
- (can't get injector wire-connector off......and anyway clicking noise should mean working solenoid)
- good, steady injector click would seem to eliminate electronic control unit (ECU - 'computer') as problem
*Injector clogged or leaking or ??*
- For clog......Sea Foam cleaner run for about 8 gallons (only, so far).....no noticeable difference.
- for leak.....ran this test: Before startup, floor throttle.....turn ign on quickly to 'start'.....immediate start means leaking injector (??)
wow !!....to 5000 rpm before i can get foot off throttle !! ........BUT.... is this a good test ????
any other leaking-injector test ?? (no black smoke from exhaust, but it's only one cyl out)
- (i'm asuming that broken injector spring lets it leak (spring closes?.....solenoid opens?) 
*One strange symptom...*.On cold start,* idle does not miss for first minute or two* (but rpm is up to about 1200 rpm, drops to 750 - miss)
Nissan factory manual says startup is in "open loop", and that ALL injectors are open at same time (and presumably
for longer time to produce rich startup mixture). Why 'open loop' might make #1 injector work at startup is ????
(as INFO: Nissan FS Manual is at lemons.bpi-us.com/manuals/sentra.....it's huge: all Sentras, including worldwide)
*What to do ??*
- replacing the injector is expensive......if it's only clogged, then maybe more time on Sea Foam fixes it BUT
- if *clog* means running lean, it could burn valve (??)
If * leak* is so bad that mixture won't fire, then >
- (1) i should hear explosion in exhaust as raw fuel hits red hot exhaust pipe ?? (miss is chu-chu, not bang)
- (2) raw fuel past rings and into crankcase is bad
any insight appreciated (TIA)


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## rogoman (Dec 16, 2004)

First test the fuel pressure like B13ER suggested. Then test the electrical resistance which should be 10 - 14 ohms; this is very important, if out of spec, they won't operate properly, if at all.

A good way to test for leaking fuel injectors, is to unbolt the fuel rail from the intake manifold and pull off the entire assembly. Keep the fuel hoses still connected and don't remove any individual injectors. Also keep the electrical connectors on the injectors. With the assembly now away from the intake, turn the ignition key to the run position WITHOUT STARTING THE ENGINE. Now observe each injector to look for leaks. There should be no drips.

You can also test the injector spray pattern. First remove the ignition coil wire to disable any spark to the plugs; safety measure! Now place a rag under all the injectors while the assembly is lifted. Have someone attempt to start the engine while you watch the spray pattern from each injector.

Make sure you have at least 4 spare insulator rings for the injectors in case some are damaged during rail removal.


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## lou abernathy (Apr 19, 2014)

*UPDATE>injector cleaner works..plus troubleshooting ideas*

STATUS >
Fixed good enough to live with....(for now)
Two tanks of* injector cleaner (Sea Foam) cleared* the steady single-cylinder miss, to just a very occasional miss...
and brought idle up to a steady 750 RPM.

*SUGGESTION (simplified troubleshooting) >*

1) For cylinder miss, *find out which cylinder(s) miss*, as follows >
- obtain a *GOOD timing light* (clamp-on type)....
borrow, rent, pay mechanic....*don't* buy cheapie light
- *watch timing flashes*, from each plug wire.....
looking for *steady, or else missing* flashes.
- if timing flashes are *steady, no gaps, then ignition system is OK*
(all of it) (I wasted $$$ replacing ign)
- * unsteady timing flashes indicate ignition problems*:...
troubleshoot> plugs - wires - cap - rotor (etc)

2) (Ignition OK) *Try injector cleaner.*......it's likely an injector problem....
be sure you get injector cleaner, not throttle body cleaner.
(on very high mileage cars, it might be a burned exhaust valve,
but that's unlikely) 

3) *Check injectors* as follows >,
- obtain a *mechanics stethoscope*........cheapie is fine (like Harbor Freight)
- follow tool instructions....a *steady click on each injector means correct* operation (you will hear it clearly)
BUT* injector still could be clogged, or could be leaking*(not fully closing).

4) If* injectors click OK, and cleaner doesn't help, the it's (probably) down to replacing injector(s)*

The GA16DE ('91-'94 ver)* looks really hard to replace injectors *>
Nissan & Chilton manuals call for* removing the upper air plenum*, as does the independent Nissan shop ($500),
which means removing about a dozen sensors, control units, and other stuff.

*Some posts say you can replace some injectors without pulling the plenum* >
*others say you can pull the fuel rail*, which holds the injectors, without pulling the plenum, BUT
that *looks about as hard as pulling the plenum*....

*COMMENTS ??*


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## BeyondBiscuits2 (Jan 18, 2006)

Have you done a compression check on your cylinders? Also, have you checked for vaccuum leaks? '90s Nissan engines are notorious for intake manifold gasket failure, particularly the GA16DE and KA24DE. I'm not convinced your issue is a fuel injector.


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