I use 89 gas for about 5-6 months, and only yesterday the car started to act this way. What worried me at first is the results of emission - last year: HC - 0.02, CO - 0.8, NOx - 0.60. but this year it is: HC - 0.48, CO - 11.37, NOx - 1.19. This seems very strange, cause on any of my previous cars the emissions lowered since I owned them.
My foundings: I removed all ing. coils: 2 had some yellow/light brown resedue (like a powder), 3 - had some cracks on coils body, spark tips were OK (NKG, I think). If there is juice leak thru those crack, why did it happen so suddenly? One told me that this could be because of a bad gas I put in last time (89 octane). The remedy to this is to add hi octane gas.
Another theory is that some of the sensors, but definately not oxygen.
or - to change the coils to see if there is any improvements. (somebody offered all 6 for 100 bucks, but, again, used ones)
I also measured an impendance of each coil and the only reading I could get is between "-" and "+" posts on the coils. The reading was 0.8 Ohm.
If anyone would point me at the right direction I'd really appreciate.
Data on my car - 1993 3.0L, DOHC, 5 speed, "free-flow" muffler, 218K miles, oil changes regulary, doesn't smoke, gives my 25-27 mpg.
Thank you...

 

sounds like injectors

 

start by fixing what you KNOW is broke (I.E. the coils) then start screwing around with the other stuff.
BTW you are supposed to be running 91 octane not 89

 

91 octane... that's right. honestly I felt no difference between 92 and 89.
I'll change the gas tonight - let's see what will happen.

Injectors?.. How do I inspect them? Remove the plugs one by one and check for current (with bulb)? Can I manually clean them soaking in alchohol?
BTW, the fuel pump is 2-3 months old...
I'll post results as soon as I'll get any ))

Thanks...

 

the 89 octane, will cause the timing to retard if the engine is picking up detonation.
of course your knock sensor may also be malfunctioning.

 

ok... today's results are not that promising: with the engine still cold it drove relatively good (I was gentle), drove a bit harder and noticed that under acceleration it behaves the same - engine shakes, lacks power, thus I used lower rpms and added 93 octate (dammit!!! there was no 94 on Shell gas station!! would you beleive this??!!). Drove another 4 miles - the same... added "octane booster" (10 points) - still no improvements.
I'm kinnda puzzled that to do next - either knock sensor or the ignition coils (about the coils - only on the left side the plastic bodies have cracks).
Some food for thoughs - when I eased on gas - the engine ran better, the idle is almost good and revving without the load didn't exhibit the very problems while driving. In my previous experience I know that Throttle Positioning Sensor (or whatever it could be called) may contribute to uneven acceleration (like jerking) due to warn contacts (but it only happens in older cars).
Off cause I can replace the ign. coils (I found them for 55 bucks each NEW), but, without knowing the rational path of actions, I could increase my enjoyment of fixing my car )))
For now, I won't drive it...
...

 

If you have cracks in the coils, it will definitely cause problems. I had one cracked coil pack and my car idled like crap and woudn't run very well. I also had bad rear coil packs, which caused my car to stall under heavy acceleration (WOT). I replaced them on my old engine and it idled well and drove much stronger with no stalling or hesitation.

A faulty knock sensor causes the timing to retard and drive a bit sluggishly, but I don't think it would cause any kind of shaking or uneven acceleration. It also tends to show itself as being faulty after being very warm (driving for 45 minutes or more). At least, mine did.

I have a spare throttle position sensor I will sell fairly cheap, but I kind of doubt that is your problem. I would definitely replace the cracked coil packs first.

 

Can you or anybody else point me in the right direction re details on the ignition timing mapping for the VG engine? - basic question being is it dynamic (constantly varying based on driving patterns, fuel used, etc) - I know the KS will help retard the timing when knock is detected, but would also like to know more about the actual mechanism used - ie - retarded by how much and in what sorta steps and for how long ? - once no knock is detected is timing once again advanced ? - in steps? - how long does it take to get back to "normal" - ie - what one would expect given ideal driving conditions.

Any dope much appreciated - struggling with a similar sluggish VG.

 

speaking of ignition timing - how can I measure dwell angle? This particular engine type is new to me and I just don't know what I need to hook the meter to... Haynes manual? ALL MANUALS BY THIS COMPANY SUCK !!! ALL...they lack a lot of info. (that's the reason I turn to forums...)
I really hope that the new ignition coils will remedy current problem.

 

VG runs on 87 octane

 

OK - but given the fact I dont have that here, what then?

 

I dont think there is any dwell to measure. The ignition is electronic.

 

:doh: I don't know how they rate octane in SA.

 

...very interesting - most of places I called don't stock these coil packs, some - have to order (and I have to wait a week before I can install them)...

 

here's what I found..
Due to the introduction of contamination resistant "pintle-less" fuel injectors, Nissan no
longer recommends using fuel injector cleaners in vehicles with injectors of this design.
Use of fuel injector cleaner on these vehicles, while providing little cleaning benefit, may cause corrosion of the fuel injector coil and eventual failure of the injector. Do not use fuel injector cleaner on the models listed in the chart below or subsequent models with "pintleless" injectors.

Model Engine
Applied model year of
vehicles with affected fuel
injectors
Altima (U13) KA24DE 1993
240SX (S13) KA24DE 1991
Truck/Path ([W]D21) KA24E 1990
300ZX (Z32) VG30DE 1993
Truck/Path ([W]D21) VG30E 1990
Maxima (J30) VG30E 1993
Quest (V40) VG30E 1993
Sentra (B13) GA16DE 1991
Sentra SER (B13) SR20DE 1991

 

Day two... As I hoped (but didn't expect), the engine runs not bad )))
I drove about 10 miles (street driving) At first was OK, then I felt this problem again, then it seemed to deminish. Back to normal. Lesson - use high octane gas (pref. 93).
Thank you all for you participation.
...

 

hmmm...The acceleration is again slugginsh, if I accelerate very slow, I don't notice anything unusual. Dammittttttt
the next step would be to replace the coil packs...

 

An easy way to check your coil packs for "spark leak" is an old school trick used on ignition systems for years.

Get some heavy duty, cheap, aerosol can hair spray. Remove and clean the coil pack with brake cleaner to remove any oil residue. liberally spray the coil pack with the hair spray, let dry and reinstall.

If the problem goes away (as mine did) you can isolate which coil pack is bad or keep running it as I have knowing which one it is!

Fred

 

I finally added 94 octane and, guess what, the engine runs well, thus the problem was with the quality of gas, not ign. coils, in addition I was unpluging the coils one by one with a running engine and, as it should be, it ran somewhat bad, indicating that the particular cylinder doesn't function.
I do worry about the injectors, for I've read that it's not recommended to add any injector cleaners to these engines (due to some changed in very injector); I'd added cleaner 2-3 times (including "marvel oil")
...