Ok, Battery was very old and when I brought it in for a load test it first tested 73% then 40% basically not hold a charge, and it was bulging at one side, had to replace it. That part had to be fixed.

I did however rev the engine and apparently it was backfiring a few times, half the tank is still 87 octane and this problem never presented itself when I had a higher octane in the tank due to adding lucus injector cleaner. I swear I also heard it coming out the intake as well but it might of just been echoing, not sure.

The spark plugs were replaced 23000 miles ago, Denso brand.


If it were a timing issue, wouldn't my gas economy be going down, and wouldn't it be doing it regardless of the engines RPM?


It seems that sometimes after a backfire the engine runs ok, then the issue might return when idling.

The issue does seem to be affected by the octane.

I did take a picture of the spark plug, does seem to be minor buildup on it.


Stressing me out, seriously.....

 

I'm telling you man, I'm strongly leaning toward the lower octane fuel being the cause, especially nowadays with regular unleaded gas having so much ethanol in it. Start running mid-grade or premium which at many stations, (at least here in WA) has less, or no ethanol content. You said it yourself - the problem doesn't manifest with increased octane.

Thats where I'd start, personally. Its a cheap potential to rule out, worst case scenario you filled up on higher octane gas and it cost you an extra 3 or 4 bucks at the pump when you'd have already needed to fill up anyways. At the very least it rules out fuel, and as suggested by another member, try filling up at a different station as well if you haven't already, he posed the idea that it may be bad gas - a valid theory indeed.

All of that aside, if you still insist on running regular, check your knock sensor - mayhaps it is failing and is therefore unable to consistently prevent knocking caused by the lower octane fuel.

EDIT: and your spark plug electrode looks iffy, probably wouldn't hurt to replace all six. They're usually fairly squared off, yours looks worn out, being shaped like a dome. Get NGK platinums, the OEM replacement. These cars don't tend to like non-OEM plugs, so the general consensus goes. Also, check your spark plug wires too, I had an intermittent misfire that would only manifest when it was raining or otherwise humid out caused by voltage leaking past the boots.

 

Did you change the PCV valve

 

On a regular basis

 

NGK copper plugs are the OEM plugs BKR6ES-11. the VG30E never ran plat plugs as OEM/factory. the VE30DE had plat plugs but they also have coil over plug ignition set up and not the dist cap and wires of the VG.

 

- reply in the same thread that you created so it's not all over the place. there's a back story in your original thread. creating a new thread confuses people.

- check the timing with a timing light..yes it's old school but these cars are old and they will need you to set the correct timing otherwise the ECU will do weird things.

- swap out the denso plats for NGK or denso copper plugs. copper plugs have less resistance and will fire easier.

- best thing to do is do a full tune up if you haven't done so already. new cap, rotor, wires, pcv, fuel filter, air filter, etc.

once that's done report back how it runs.

 

Your totally right, sorry, had my cars mixed up. Derp, I had no real excuse there LOL I just replaced my own plugs last weekend with NGK coppers.

 

it happens to the best of us.

the only real benefit of running plats is longer service life...otherwise coppers are good for me..esp with boost. so easy to change them on the VG.

 

Sorry, I was derping badly last night.

 

thats the thing alot of people forget, they didnt have platinum plugs decades ago. usually better to use copper

also yeah try to run 91 or higher octane, many places dont put ethanol in their 91. ethanol chews up the O-rings on old Nissan injectors

 

Amen brother

 

Either mid-grade or premium but never regular. I use mid-grade most of the time if not premium. Just do what Danny suggested and report back.

 

Ok, im a noticing it is actually having more difficulty with higher octane fuel, and I still get backfires, this proplem only occurs at lower RPM's.


Now, any time I had Lucus engine oil in the system, the car ran fine, no real stumbling, decent power etc. I know that stuff lubricates, is it possable that there is crap on my intake valves and the lucus just completed the seal? I know some say if there is, you have to use sea foam to remove it, but others say it is sort of useless. Gonna do a compression test tomorrow and see.


I know a valve job is rather expensive, even for just cleaning them.

Spark plugs and wires are new, distributor rotor and cap in decent shape. Only thing I really have not replaced yet is the pcv.

 

Take it apart and clean the plenum if you have not done it chances are its just dirty you need to replace the Pcv valve every oil change

 

Ok, compression test revealed about 190 psi exact in each cylinder, less i was reading it wrong. though I did notice that my new spark plugs were a little blackened, hmm..

I am going to replace the pcv once I can be sure the liquid wrench will get it loose (do not wanna break it), now do I need a special hose of any sort, they gave me one that matched the pcv and appeared thick enough, or should I order the specific one(old hose is very hardened and I worry it may crack or break).

I have never done a timing adjustment before, the reading showed the arrow is on the opposite side of the one with the red marker, though it seemed to move a bit to the next notch over. Maybe 20 degrees or so, I'm not sure what the increments are. The last time I looked at the distributor cap and rotor I looked ok, maybe I missed something.

 

if the car has run fine for years and nobody has recently touched the distributor, i wouldnt look to timing being the cause of running poorly unless the timing belt skipped a tooth

take a look at the dizzy cap again. couple years ago my Supra was running like absolute *****, ripped my hair out trying to figure out what was up. after replacing various things, got frustrated and started ripping stuff apart. distributor cap had a crack on the backside and was causing the problems

shouldnt need a special hose for the PVC, petrol lines etc need special hoses but for the PVC if its the same size and length of the old one its fine

 

MAF sensor was bad yet looked very clean(old car is old), also the fuel injectors were dirty.