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Discussion Starter #1
Hi all!

Here's the lowdown: I have a minty 94 G20t manual that has recently started misfiring then cylinder 4 (closest to trans) wasn't giving fuel at all (pulled spark plugs lead while running no change and could see arc. New plugs too. Checked resistance on the injector and it was toast. Bought a brand injector and installed and she was purring like a kitten.

Nowwww today same cylinder wasn't firing and it is backfiring on deceleration.

I don't want to just buy another injector to have it do it again (and installing is a pita)

Help pls
 

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Wiggle the fuel injector wiring while it's running. You may have developed a short in that injector's wiring.

Another possible problem is the o-ring on the new injector is leaking. If that's happening you should smell fuel. That could cause backfiring.

(and installing is a pita)
I feel bad for you. Replacing fuel injectors on a low port engine is far more difficult that it should be. I hate Nissan for making such a repair so difficult. The high ports are easy in comparison.
 

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Discussion Starter #5
just curious there are 2 different looking injectors for the same part # (I am ordering 4 new)

1:


2:


My car has the second kind. Would the inlet filter location be a problem?
 

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Unless your car has over 200k, there's a much smaller chance of an injector being the culprit of a misfire issue. If you're going to take the approach of throwing parts at it first, I suggest process of elimination from the cheapest and even free sources first.

1. Look up how to set the base idle timing, and set the car to 15 degrees (requires timing light and adjustment of the distributor with the car in timing mode, there are many how-to threads out there)
2. Not sure where you're from, but if you're anywhere near the rust belt, pull open the fuse box under the hood near the battery. The terminals to the ignition fuse are notorious to corrode, if you have a soldering iron, some extra time and patience, cut the cancer out, and give your ignition coil/system a new life.
3. Dist cap and rotor : If you're really cheap like me, simply pull the cap off and clean the points with steel wool especially if you see points corroding under here. If this makes a difference after a few days and the code ends up going away, pick up a new cap and rotor

I did this to a P11 that was sitting for a few years and that I DD now, which had a misfire issue when I first purchased the car. Issue went away immediately.

My personal opinion, but I think many people would agree. I highly recommend to stay away from rebuilt or aftermarket injectors. Usually the OEM ones will last longer and perform better, find an extra set on the cheap, and pay a good service to professionally sonic clean them.
 

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Discussion Starter #7
Thanks for the long and detailed response. I guess I should clarify more in that its not misfiring as much as cyl wasnt firing at all. The car does have near 200k on it.
 

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Thanks for the long and detailed response. I guess I should clarify more in that its not misfiring as much as cyl wasnt firing at all. The car does have near 200k on it.
Gotcha, makes sense then. I reconditioned a set of side feeds awhile back, and made a thread about it. https://www.g20.net/forum/showthread.php?116320-Mr-Injector-Injector-Side-Feed-Kits-Feedback-thread Sometimes you can save an injector that isn't burnt out. Having all of your injectors flow tested and sonic cleaned could be a good preventative measure of making sure none of your other injectors are on their way out either.

Some good info in that thread too about replacing the annoying phillips head screws (a lot of people strip these out) with some hex ones.

Good luck.
 

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On the connector on the plenum (top left) for inj. Grounds #8 is for cylinder 4. Maybe corrosion or something dripping. Maybe spray it with some air duster on the back or inside. Either way look all inside F100 connector.
 

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Shouldn't backfire on deceleration, you would be in fuel cut. Make sure that injector isn't leaking (dirt in needle, shorted, etc) or a torn o-ring like Nissandriver said. I would find it highly unlikely (always a chance) that there is a mechanical issue (timing, compression) if the misfire went away after the injector was replaced.

Still, listen to ferrari21, and do your mechanical checks. Make sure that your timing is correct and compression is within acceptable range as one and as a whole.
 

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Discussion Starter #11
Hey everyone thanks for the information, assistance, and help :)

Alas, after replacing plugs, fuel filter and the injectors, the car ran amazing for 1 day. After work, I went in and the car had a hard start (took 5 seconds or so of turning over and giving it a bit of gas to get started) and sounds like it is misfiring a bit again (runs on all 4 cylinders now though so thats good). It is also backfiring on decel again. YAY.

Just an update with what is going on, and more info about how it started:

1) This all started after I replaced the clutch. Before that I had zero running issues. (If its something I did I just want to know what :eek:)
2) I have a knock sensor code P0325
3) I remembered that when the car was down for doing the clutch I jumped the fuel pump relay to get some gas for another project I was working on (lazy should have gone to gas station i know)....Could that be part of the problem?
4) EGR has been deleted (plate made and header plugged and resistor put in for egr temp sensor. (no egr codes so far)

At home after work the car is idling (a bit rough) and I unplug the o2 sensor on the header (no change).
I unlpug the maf and the idle smooths out a lot, but give it any gas and it runs like doodoobird.

All of these together and me reflecting with a nice glass of willet bourbon on what everything has been (pretending to be shirlock holmes of mechanicalness) leads me to deduce that something I did during the clutch change is causing the issue. I do not regret changing the injectors and whatnot seeing as how the car has 196k miles.

Any paths to go down to eliminate issues I would greatly appreciate. Here is my plan for this weekend:

1) Spray bottle around intake manifold and intake tube to see if idle changes and finds vacuum leak
2) Check that knock sensor on back of block has continuity between ground and A. Also check that sensor and sub harness are plugged in correctly and have no breaks.
3) Check all grounds (I need a diagram)
4) Remove and examine fuel pump and look in tank for sediment. Also check fuel pump resistance and operation.

Any other ideas would be greatly appreciated. I just want to drive this fun car :)
 

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You could cut "back up battery power supply" to the ecm. Pull the wire from the connector and wrap it. don't actually cut it. It will run factory presets and will never learn to get better. But its sounds like 2 warm up 2 cool down and the problem comes back. So it is electric. It's not the pump because at 1st was good then went back the same. Nor mechanical timing. Check throttle position, coolant sens, maf, any ground you can find. FSM is huge help. And if you can , put that EGR back on and fix the leak if it was leaking. If your on stock ecm, it will run lean without it. There is ecm grounds right on the intake top. Start with cleaning those too.
 

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Discussion Starter #13
Ive tried to get the fsm with the link to where it was but its not working, even with waybackmachine. Thanks MFN!
 

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HUmid weather? Point-based ignition system. Check seals, water in the firing system can cause this. Leaky valve cover gasket, bad seals on distrubutor (seal on exhaust cam end and also on the cap end). Spark plug wires or boots could be cracked and allowing moisture in.

This appears to be a conditional aka intermittent (not constant) problem hence my suggestions in checking out the ignition system.
 

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HUmid weather? Point-based ignition system. Check seals, water in the firing system can cause this. Leaky valve cover gasket, bad seals on distrubutor (seal on exhaust cam end and also on the cap end). Spark plug wires or boots could be cracked and allowing moisture in.

This appears to be a conditional aka intermittent (not constant) problem hence my suggestions in checking out the ignition system.
I'm still leaning towards the misfire being more of an ignition related issue too. Still haven't heard a response regarding the check for base timing, nor a check under the hood fuse box by the battery. Really need to look at that 12v supply wire to the ignition coil, so many people throw money at plugs, wires, cap, and rotor, and on a lot of older G20's I've seen, the terminals for the fuse are so bad, I'm surprised the coil is getting any power in the first place.

Here's a picture of the underside of my fuse block (under the hood) when my work in progress was getting a misfire CEL code. Took some time pulling things apart and resoldering with some fresh wire, but it was free, and even when I still had a worn out cap and rotor (new wires and new plugs, I think), but misfire code cleared.
 

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Discussion Starter #19
UPDATE:

Thanks guys, i did those checks. Found that cyl 2 was now not firing injector... that one was dying too. I replaced it and then I took the injector harness out and unwrapped and inspected. The knock sensor plug was trash and the wires exposed and gross. I repinned and cleaned it up and it seems to be running better now. It does have a fluctuating idle so I am going to clean the IAC and TB.

Ill let ya know.
 
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