Hello

I have an 03 G35 that has been sitting for 2 years. I did a timing chain and valve stem job on it. The car starts and idles but has a constant misfire. When I use my scan reader the only code i get is P0300; there are no other timing related codes. When i look into live data my short term trims go from 0 to 25 positive on bank 1 and 0 to 25 negative on bank 2. The long term stays at zero.

My code reader (Bluedrive) doesnt show timing advance for bank 2 but at idle the timing stays at a constant positve 14 - 16 degrees on bank 1. With the key on engine off timing advace shows 63.5.

MAF reading is around 5 g/s. The wiring was repaired by someone else. The sensor wires for the IAT and MAF were swapped but I swapped them back.

Does anybody know what could be wrong. I dont think the timing is wrong because there is no cam timing correlation codes.

 

I would start pulling plugs to inspect for which cylinder is misfiring. You can also unplug coil pack harnesses to try to isolate the issue.

Nissan Datascan 2 (PC version) makes this a pretty simple process since you can just turn off cylinders individually.

Ignition timing advance isn't separated by banks, it's just one set timing advance that will vary from like 14 to 45 depending on rpm.

 

Do you know what would cause the opposite short term trims and no long term trim change? Is that a fail safe when there is a multiple misfire?

 

Also keep in mind that every misfire is sending a LOT of raw fuel into the exhaust which is going to cause the ECM to read that bank as extremely rich which will pull more fuel from that bank. The side that's going negative value on fuel trim is probably the bank that has the misfire.

 

Hi. Checking my spark plugs confirmed that bank 2 is running richer than bank 1. Disconnecting each of the coils yielded a similar engine stumble on all cylinders. This

Investigating further I bought a new Bank 1 Sensor 1 because it was a little lazy. This has made the misfires a little better.

I have also checked the fuel injectors to see if they are OEM for a 2003 Infiniti G35 MT. They are purple FBJC100 injectors. Can anybody tell me if this is correct?

 

Yes the FBJC100 is the factory injector.

If all the plugs across a bank looked the same and you couldn't obviously find one that was burning different on a bank then I would start to suspect the upstream O2 sensors were going bad or just getting really lazy in their cycle.

Start by just removing and cleaning them, soak the metal end up to where the hex head for the socket is (so basically not getting the wire end wet) in fresh gasoline for 12 hours or so, after the soak gently shake it in the gas to remove the loosened particulates, then dry thoroughly and reinstall. Usually works pretty good for lightly clogged O2 sensors.

Also smoke test the exhaust to verify there are no exhaust leaks at the header to engine.

 

Yes both Sensor 1 on each bank are brand new NTK 24401. I have a Z1 High Flow Cat. Vacuum testing the engine shows a stable vacuum of 22 or so InHg so i don't believe the cats are clogged. Bank 2 Sensor 2 also is reading very rich while bank 1 sensor 2 reads about .230. I haven't driven the car only idled it for less than 30 minutes a few times so i hope the cat is still good. There is a P0037 code so it probably just needs replacement.

 

Ok if you're also throwing the heater code then I would start by verifying you have complete circuits, test continuity on each wire to the O2 sensor, I think there are two wires that go to the IPDM and 3 that go to the ECM. Check the FSM for the schematic.

If the wiring is good then it's a bad sensor.

 

Cleric670 I have found your posts in many threads extremely helpful. My 2003 G35 couple with only 70 thousand orginal miles was misfiring and the code was for cylinder 5. Spark plugs were replaced with NGK 4469 {#BY481LFR5A, LFR5AIX11, MZ602090} Iridium IX Gap 0.044" and coil packs HITACHIIGC0007 {#22448AL610, 22448AL615, 22448AL61C}. During the install oil was found in cylinder 5 and 6 only. The oil was cleaned out of the cylinders and then the spark plugs and coil packs were installed. The car was still misfiring and so I decided due to the oil issue to purchase OEM valve covers and gaskets. When dropping off at the shop and giving them the symptoms they wanted to do a compression check (possible blown head gasket) on all cylinders and they reported everything was good. At the same time the shop decided to check the status of the fuel injectors and noticed when 1 and 4 were turned off the car ran with no misfires, but when not off the car idled and shook. Do the symptoms and the testing they done sound consistent and should I go with replacing all fuel injectors and also the valve covers and gaskets while I am at it since there was oil in the 2 cylinders. Will the following fuel injectors which are not OEM work HITACHIFIJ0020{#166005L700}. I don't know how worried I should be with using these fuel injectors if that happens to be the real issue. Based off the overall symptoms do you have any other suggestions to inform my mechanic about?

 

I would not mix fuel injectors unless you flow test ALL OF THEM to verify they all have the same flow rate which is HIGHLY unlikely.

Reason being, the engine doesn't correct fuel mix per cylinder, it's per bank. If you have one injector supplying 10% more fuel to one cylinder it's going to read the entire bank as rich (only two O2 sensors, one on each bank) and when it pulls fuel you will then have two cylinders running lean.

Replace all 6 if you think that's the issue. Personally I'd keep working on other possible causes for a random misfire like clean the MAF, smoke check for vacuum leaks, etc.

However, 70k original miles means this car spent a LOT of time sitting without being driven. Sitting means gasoline begins to varnish, you can definitely have injector problems from a car that routinely spends several weeks without being driven.

Try running TWO BOTTLES of Sea Foam fuel treatment through it, yes two bottles in one tank of gas. It makes it a bit stronger (they recommend 1oz per gallon for maintenance, 2oz per gallon for cleaning, our tank is 20 gallon, thus 40oz for cleaning, the bottle is 16oz so two bottles is 32oz total). Might clear up injector problems, don't get your hopes up but it's a heck of a lot cheaper than a full set of quality injectors.

Also start calling around to local shops that have an injector cleaning machine if you can remove them yourself. You can get them like 95% clean with one of those ultrasonic cleaners and an injector spray machine.

 

Thanks for the reply and early early back around 2003 and on until I bought the car in 2012 there was at least 2 to 3 years it sat for almost the entire time. While I was on deployment for months at a time it also sat. Now I bought it in 2012 when it had already been 9 years old and it had only 20,000 miles and since the last almost 10 years I have only put 50 thousand miles on it.

Like an idiot when it was misfiring I did drive it a few miles a day as I live on the base I work on and a couple of occasions maybe 10 to 15 miles for a couple of months. Do you think there is a good chance the oil that was found in 5 and 6 impacted the fuel injectors or the fuel injectors might have been the problem the entire time? I have purchased the following fuel injectors from Rockauto and they say OE Hitachi HITACHI FIJ0020 and they were 50 dollars each. I also found this website which has been in the game of cleaning and refurbishing fuel injectors for years and so what is your thought Recondition & Return Service (motormanfuelinjection.com) and they also sell OEM refurbished or would the Hitachi new ones be the best bet?

Thanks again,
Aaron

 

New or rebuilt to new specifications doesn't matter tbh, the only thing that matters is that they have the same flow rate and are very close to OEM spec (for base tune), the ECM will manage long term fuel trim to correct anything within +/-25% but they need to all be flowing the same gallons per hour.

Oil in the spark plug well tubes can DEFINITELY cause misfire though, the coil is delivering roughly 13k volts which needs to all be delivered through the spark plug into the combustion chamber, if voltage is leaking out because the whole assembly is submerged in an oil bath then you will NOT be getting the full 13,000 volts to the combustion chamber. The engine management in stock form is pushing pretty lean on the front two cylinders (due to the air volume deficiency of the plenum), and these engines are notorious for pulling timing due to knock. Adding a misfire condition due to oil saturated coils is only going to exacerbate the issue.

You might also be developing pump issues though, especially if your misfire condition only happens at higher rpm. Sometimes it's just the strainer baggy on the pump.

 

Good morning and thanks for th reply again. I have not experienced the misfire more at higher RPM's than lower RPM's. There was also a week period and it was really wierd where the car did not misfire to the extent it had been and instead drove like it was almost back to normal. Have you heard of this and what is the usual cause when that scenario exists. I am really just trying to nail down the issue for the misfire as much as possible before spending tons of money.

 

Honestly I would buy the fuel damper sandwich adapter from Z1 Motorsports so you can actually test fuel pressure (might as well just get the one with the gauge on it). Then see if there's a fuel delivery issue.

Next pull all those new plugs and inspect them for any difference per cylinder, this will at least help narrow down which cylinder might be problematic and you might find another issue while tearing it down like oil in a spark plug well or something like that.

Plus THOROUGHLY inspect for vacuum leaks.

 

So thanks for your help and reporting that replacing the fuel injectors and replacing the valve covers fixed the misfire issue, but was hoping you might be able to provide some insight for the gas smell coming from the exhaust. It is not really impacting my fuel mileage at all, but definately a pretty strong smell. I have no error codes also.