Hello guys I have an 05 Infiniti g35 Coupe with 113,000 miles.
All was well until one day the G started misfiring heavily and went into limp mode. Thankfully my parking spot was 20 feet away, and at that point I parked her and she sat there for months until I had time to diagnose.

----------- months later --------------------------------------------------------------------------------------------

put new gas in and right before giving up she started back up, but was in limp mode, couldn't get over 10mph or 1500rpm.

a week or so later I brought the G to a local mechanic who then told me my timing chain was broken... lies

I then towed the G back to my garage and began my own diagnosing...

changed:
spark plugs (found oil in 4 and 6 assuming it's the valve cover, planning to change this week)
Crank position Sensor
PCV
Oil change
Full tank of high grade fuel with Lucas fuel injector cleaner
Clean MAF
checked for vacuum leaks with a stethoscope (none)

At this point she was running again but would misfire at various rpms, but not without load.

I didn't know what to do next so I took the G to infiniti for guidance.

They ran a diagnostic and returned to me with two codes that they presumed to fix the misfire.
p0345 Camshaft position sensor bank 2 and
p1283 upstream air to fuel ratio o2 sensor

and also a code for the spiral cable.

I went to the auto parts store and bought the two sensors, both OEM and then proceeded to install them.

After installing she started up well and sounded good in park, but as soon as I put her in gear she misfired horribly. It sounded like marbles being dropped into a tin can.
Then I checked the spark plugs and all were clean but 4 and 6

changed coil packs for 4 and 6, but the symptom continued so I then swapped the old CPS back in and the misfire code went away but this misfire did not. but new codes appeared.


P0345 CPS
P0037 Heated oxygen
P1065 ECM backup circuit

my thoughts are it could be the fuel injectors, fuel pump/filter or the ecm is bad. another theory is that one of the resonated pipes on my exhaust has deteriorated inside and causing restricted flow and a bad reading for the o2 sensors.
Where should I start or should I go back to infiniti...


any input is appreciated. thank yaa

 

Sounds like leaky valve covers. Thought I'd see an old rusty 200k mile G, this is too nice not to be running!

 

So far so good!


Why didn't you return to the dealer instead of guessing?

Perhaps your cats are clogged but continuing to replace random parts by guessing without a pro to find the root cause on a 12 year old vehicle is going to be a huge waste of time and money.

Just my $.02

Telcoman

 

You said you bought OEM sensors at an auto parts store but in my experience that isn't possible. Our cars don't usually play well with aftermarket sensors so you might check into that but I'd probably take it back to the dealer for a true diagnosis before replacing anything else. I'm not usually fan of the dealership but sometimes they're our best bet.

 

Hey guys thanks for the responses! and yes it is probably more effective to bring to the dealership to have them fix it, but as I may have not made clear I already did. They told me to replace the CPS and the upstream 02 sensor. I could have payed them to do it but they wanted over $1,200. I figured I could do exactly what I would be paying them to do but for 1/6th of the price. Plus, everything I tried after the fact was of low cost. The G actually only has resonated test pipes leading to the cat back so maybe something is loose in there. In regards to the sensor response, from my knowledge many auto parts stores do sell OEM parts, my concern is that maybe I got a dud, even though it is unlikely, I personally know it is possible as on the old motor I installed a new OEM sensor and it didn't work, bought another new one from somewhere else and it fixed the issue. Needless to say its electrical, there can be flaws

 

Test the sensors you bought. Typically the FSM has a test procedure for most sensors.

If you have a Bluetooth OBD-II reader you can also look at real-time voltage readouts from each of your oxygen sensors and see if one is bad as well as see the readouts from many other sensors.

 

I do have a bluetooth reader so I will check that out when I get back in the states! putting my issues on hold for a week out here in Barbados

 

I had a problem similar to this. The problem with mine was anytime there was a large temp change in the weather the car would start misfiring and would run pretty rough for a while. Then the problem would disappear. I tried all kinds of things, plugs injectors, injector cleaners. This drove me about mad. I even thought I fixed it a few times.

In the end it was a faulty relay. It finally went out and the car went in limp mode. Unfortunately this relay is on the relay box(what ever its called) behind the battery. Even though the relay is fairly common on nissan/infiniti vehicles, it is always on that box. The dealer wanted like 600+ for the relay box and did not sell the relay by itself. It was not sold at parts stores either. So I hit the junk yards and looked in every vehicle till I found the relay and grabbed like 20 of them .

I no longer have the car now, but I still have the relays. I will see which one it is and post it here tomorrow, maybe it is the same problem you have. Unless you fixed it already.

 

It is the OMRON model G8VL-1A4T-V relay. I see them on ebay for 12-30$. I should sell mine. I may have 20 of them

 

hey thank you for sharing your experience! Could you please clarify the symptoms you were having as far as the misfire? I live in Florida and its pretty consistent with temperature, but **** if it could be as simple as a relay, how would one diagnose this? Or is changing it the only way to know? I have been to infiniti dealership and they said nothing in regards to the relay.

 

UPDATE:

so I have been traveling a lot and working, but finally got a chance to save up some $$$ and planned to take it to the dealership to get raped financially, but leave with a working G.

So I towed her to infiniti and they began to run another diagnostic. I wanted them to spend a few hours to check everything under the hood to give me a detailed description of all the things I could replace.

so i get a phone call and they tell me to come in and have a meeting with them about my car.
they begin to tell me the car has been worked on so much, yada yada yada. and that the harness is extremely damaged, and need too be replaced before they could tell if it was the ECU or not.

note there are no codes being displaced other than the p0300.

So after hearing this I got the G towed home.

finding a used harness from a G for about 150 bucks, and my buddy and I swapped it in about 4 hours, without pulling the engine. no change in the misfire.

actually to our surprise, or maybe not, the replacement harness and the harness that was originally on the were practically identical. I couldn't find any signs of "damage". so that pissed me off especially after infiniti said to repair it, it would take them up to 10 hours! @ $150 a hour! WTH.

now that I am sure it is not electrical,
after checking to make sure the following are good:
spark plugs
coil packs
no vacuum leaks
CPS sensor


now I believe it could be the fuel injectors or the fuel injector harness, plan to change those this week.

Infiniti did mention my ECU could be bad, but given how honest they are, I question it. I get no codes referring to the ECU and my misfire is only on acceleration, not in park or idle.

I think its injector related because I had a very interesting idle, It almost seems like a cylinder is cutting in and out in addition to one being out all the time. needless to say she is driving extremely sluggish. Also, spark plugs 4 and 6 have black tips, indication improper combustion.'




I would hope this is the end of the saga, simply I am not sure what else could cause this.

If anyone has any input, similar experiences or any experiences relating to bad fuel injectors please feel free to share, it would be greatly appreciated!

 

Sorry for late reply. My experience with relays is they won't throw a code until they fail. But I have not had many fail on me, actually this was the first one . I will copy and paste what I put in another thread and other things I found/did when I was trying to figure this out.

This went on and off for a little over 3 months. The first few times this happened there was a somewhat large temp change, which had to be an electrical problem somewhere. I was even thinking maybe the ecu was going out. One day it started missing again, then immediately went into limp mode. I was able to get it home and pulled the codes.

I can not remember what the exact code was, but it pointed to a relay on the box behind the battery. It is called the IPDM. It took me quite a while to find this silly box from wiring diagrams and also calling Infiniti to see what the name of the box was. BTW it was like 700$ give or take from them. They don't sell the relay's nor anyone else. Which is bothersome because this one is used in a ton of applications. Image below for the location and what it looks like.

There were times where it misfired for a couple seconds to several minutes. I fixed this last mid year and never had a problem with it since. TBH I am not sure how or why that caused a misfire. I checked a schematic of the box and I was even more lost. I can not remember which specific relay it was, but I think from looking at this picture it was one of the lower right 2 which is the Throttle control motor relay and ecm.

 

I forgot to add, not only did I replace the injector, I also switched it around with other cylinders to verify it was not a sticking injector with no avail.

 

well guys I just did a compression test and it looks like my cylinder 4 is low. 75 to be exact, the others all were 210. I added a little oil to cylinder 4 and tried the test again, no change. does this mean head gasket? and at this point is it better to swap a new motor, being that the head gasket went out once, it may go out again after being repaired.? or should I just sell the thing as is :/ I don't want to but might have to if it doesn't get resolved soon.

 

My Nissan Frontier started that, it was the crankshaft position sensor. But, mine threw the code for it.