One Injector Possibly Not Firing?

[75coupe]

Its running a pfc, and while it was tuned atleast three years back, it hasnt had any probs.

Im thinking ill have a play with some wiring and see if it changes idle at all... Just wish i had more time to play cars...

[portaz]

Rb's are very sensitive to grounding issues as I said unfortunately however hard to hear more than likely it's something you un knowingly did just re trace your steps it could be the silliest thing

[Ben C34]

The vct plug is pretty much above the top radiator hose pointing towards the engine. Looks similar to an injector plug.

[75coupe]

Oh ok, thanks for that, im going to search for a wiring issue

[89CAL]

Yep, front of the head, sticks out about 50-70mm and has a red/black plug on it

Pull that out and see if it either fixes the problem, or makes the problem constant. If so then not so bad news, might just need a new VCT Solenoid/Switch (this thing your unplugging) or a minor re-tune just to touch up the VCT issue. Perhaps a mix of both

[FBRacing]

Start the car. Take a screw driver and put the metal tip against the injector. Put your ear to the end of the handle. You can hear the injector clicking, it's working. Go thru all 6 and learn what to listen for. This is the first step of diagnosing a bad injector. Step two is ohm resistance. With the motor off, unplug the wire clip to suspected faulty injector. Use a multi-meter to read ohms. You're looking for anything that is not in the 14 ohm area plus or minus 1.5 ohms. You'll use both prongs of the multi-reader and touch each of the injector electrical prongs. Polarity won't matter. This will tell you if the electrical coil is bad inside. Unfortunately they cannot be rebuilt and the whole injector will needed to be replaced. If replacing a single injector, it's wise to remove the rest and having them professionally cleaned and flow matched to the new one.

[iruvyouskyrine]

Are 14 ohm considered high or low impedance injectors?

[FBRacing]

If you have side feed injectors (i.e. stock or aftermarket), yes they will be high impedance. If you have top feed injectors, you could be running lows. You can only run lows using an aftermarket computer. Stock ECU only runs high impedance.

These are Nismo 550cc side feed at high impedance.

These are aftermarket top feed that can be high or low impedance depending on your personal engine build goals. Easy to spot. The stock side feeds are purple in color if I remember right.

Here is a website that can help you more with specs:

http://webbersrbguide.com/index.php?option=com_content&view=article&id=64:skline-rb-standard-injectors&catid=45:wiring-electrical-a-ecu&Itemid=23

[75coupe]

Yep ive done the screw driver listen and also the swap, injectors are fine it seems so its electrical or vct, ill check it out further and find an answer...

Thanks for all your input it is much appreciated, just wish i could dedicate more time to it...

[iruvyouskyrine]

If you have side feed injectors (i.e. stock or aftermarket), yes they will be high impedance. If you have top feed injectors, you could be running lows. You can only run lows using an aftermarket computer. Stock ECU only runs high impedance. ImageUploadedBySAU Community1404537253.775014.jpg

These are Nismo 550cc side feed at high impedance.

ImageUploadedBySAU Community1404537364.267047.jpg

These are aftermarket top feed that can be high or low impedance depending on your personal engine build goals. Easy to spot. The stock side feeds are purple in color if I remember right.

Here is a website that can help you more with specs:

http://webbersrbguide.com/index.php?option=com_content&view=article&id=64:skline-rb-standard-injectors&catid=45:wiring-electrical-a-ecu&Itemid=23

Thanks for the link mate, very helpful

[75coupe]

Ok im still trying to sus this out, ive tried unplugging injectors one at a time and all make a slight difference to how it runs, ive changed spark plugs, removed coil plugs ones at a time each makes a difference to how it runs...

[75coupe]

Removed cas plug made a small difference but still rough either plug in or not

[75coupe]

I havnt had a mechanic do anything on my car other than tune or fab work for years, normally do everything myself, but i may have to bite the bullet cause this has stumped me... Silly cause i feel i caused it.

Could an electrical issue cause by moving old heat and weather affected wiring harness...

[75coupe]

And on a short drive it feels held back and knock was 50, which is completely abnormal...

Is it dvsjez time???

[scotty nm35]

Do you have a fuel pressure gauge on it? Could it just be the filter is blocked? I have seen that cause too many times recently.

[75coupe]

It could be, but the filter isnt that old, and it was running fine before painting some parts...

But now that youve said that perhaps i should change it just to be sure...

[75coupe]

No fuel pressure gauge, i do have one for the new fuel setup but its not time yet

[scotty nm35]

It could be, but the filter isnt that old, and it was running fine before painting some parts...

But now that youve said that perhaps i should change it just to be sure...

Put a mesh 40 micron on there, all the blocked ones I have seen lately have been Ryco style paper ones. Never had an issue with stainless mesh filters.

[75coupe]

Yep was going to use one or two stainless filters for the next fuel setup

[Ryno]

It could be worth checking the contacts on your ECU plug. I had a similar issue with one injector not firing and it turned out to have a bad connection for that injector on the ECU plug.

I closed the female connection a little, plugged it back in and the problem hasn't resurfaced.