(FIXED) 1997 Infiniti J30, 3.0 V6, Intermitten RICH Condition on Both Banks

Tow auction car. 179k Miles. 3.0 liter VG30DE QuadCam. Car presents very well inside/out (was not neglicted looks like it was loved). Behaved during auction podium viewing. Behaved when car was driven off lot and left idling on street for several minutes. But suddenly, misbehaved and idled very rough at red lights and stalled twice on the 25 min drive home. Made it home (yeehaw).

Checked for DTC's. Only 3 Stored codes.
-P0400 Exhaust gas ricirculation flow.
-P0325 Knock Sensor Bank 1 Circuit.
-P1443 Canister Control Vacuum Check Switch.

Checked live scan data on idle.

-Misbehaved again while in park and idling. LTFT went full negative (-18 to -25) (RICH) on both banks. Exhaust smelled like fuel.

For those wondering, car does have total of FOUR O2 sensors, 2 sensors for each bank post/pre cat. All four sensors respond to snap throttle. (No fixed signals).

Both banks would switch back and forth from OL-DRIVE to CL when opening throttle. Car will not go into and STAY in CL on it's own.
LTFT were all over the place. Showing normal ranges within -10/+10, then suddenly going full Neg ( -20 to -25) then back again. Not a consistent problem.

One thing I noticed was 170 degrees was the highest I could get the ECT to display. I was hoping to see normal operating temp of around 200-210 degrees.

Took car for a test drive around my neighborhood. ECT temps dropped to 167 degrees and refused to display higher than that. Both banks were still switching back and forth from "OL-DRIVE" to CL even while driving the car up to 45mph.

I've attached a vid and some screen captures. Thanks for any input!

VIDEO

Capture 1

Capture 2

Capture 3

hi all I know is fuel trim adjustment is based on o2 input to pcm the fact you have open loop cutting in and out should be focused on that is the direction second the rich condition might be addressed in when you find reason o2 signal is cutting out maybe watch o2 signal during koeo sensor signal integrity should be checked maybe

Not a bad idea. That ECT is really bugging me though. Not saying its the cause of my weird idle woe's... but I know ECT can have a direct influence on fuel trim and cause all kinda of goofy things to happen. It's pretty easy to check with an iR temp gun... Don't have one, but I think i'll grab one today. 168 degrees is too low.

UPDATE: Removed all 6 plugs and all 6 are fouled with black soot. All 6 injectors stuck open? I think not.

Regulator/Regulator solenoid seems most likely. I'll bypass test the solenoid (easiest to get to) to see if it's working. The regulator itself is buried behind by the firewall... won't be easy to replace.

How do you guys test a stuck closed regulator? Thx.

PHOTO of fouled plugs

VIDEO of car being naughty.

Sry for getting a lil rambly in the vid...it's a bad habit...was a little frustrated with my phone.. didn't have time to edit so just threw it on here. I'm MOSTLY to the point.

Thx again for input guys.

UPDATE to the UPDATE: Just fact checked myself on this car... the "regulator" I was looking at was actually the EGR vavle... DOH! Pressure regulator for the fuel doesn't have an electric solenoid... DOH!

Still though... Fuel pressure regulator (which is easy to get to, right atop intake runner) is my next check. Will update.

I had a little Nissan GA15 that had the thermostat stuck open - it never went above 1/3 temp on the gauge and used about 10% more fuel than when it was replaced - that wouldn't make your engine run rough but is worth looking at replacing.
Then I had another Nissan that would occasionally run rough and foul up the plugs and sometimes would crank but not start - it was a bad temp sensor. First time I've seen an engine too rich to even start. Live data was showing "-30" when it wouldn't start. Perhaps do an I/M readiness check which may tell you why it won't stay in CL.
With regard to checking for a stuck regulator - I suppose fuel trims are one of the things that will suggest that besides actually fitting a pressure gauge to the fuel rail.

Interesting, a temp sensor causing a flood. Sure sounds like what's happening to this car but I haven't proved it yet.

This car's got two FPR's and with them both disconnected from vacuum, the car continues to exhibit the same symptoms of an exaggerated rich condition. They don't leak any fuel from their vacuum ports either.

Also, as stated before, all four 02's react both rich and lean on scan data when snapping throttle or when changes between OL & CL occur. Which reminds us that once again, this issue, though severe, is intermittent. Just this morning I had a smooth lovely drive around the old cemetery with stable FT trim numbers and no symptoms.

Ideas? It's getting edgy now. The oil reeks of fuel and I think I'm starting to hear a knock develop.

Should I disconnect the ECT sensor and see what happens? Take it out of the equation? Not sure what the PCM"s protocol for that would be.

Might be worth scanning to see if any codes have returned. I think when the oil has fuel in it you can get problems with it running too rich on those fumes through the breather hose. For there to be fuel getting into your oil I wonder if it could be the temp sensor playing up and causing over-fueling - I'm not sure if unplugging it would simply take live data to "-30 degrees celsius" and cause more over-fueling or if the ECU will simply run open loop on temp - might be worth testing the theory.
As per my signature this area of diagnostics is still something I'm exploring and trying to improve on and sometimes more experienced people may roll their eyes at my comments but .... I'm trying

P1443 Canister Control Vacuum Check Switch
Try pinch off the evap purge line to the intake.
Possible excess fuel from evap canister.

Would an EVAP purge issue cause that severe of a rich condition? We're talking raw fuel coming out the tailpipe. I'll check it though.

That sounds extreme enough to be an injector sticking open or maybe an injector wiring shorting to ground. But then you'd wonder why all the spark plugs look the same. Unless they are all injecting too often for some reason?

UPDATE: More progress made today.

Swapped the oil for some used oil I had laying around. I know that sounds bad, but the oil in the car was over saturated with fuel from cylinder washing..and being thanksgiving, not alot of places were open. I wanted to do my part to protect the engine. But, If I fix this car, i'll put some fresh oil in her.

Bit the bullet and paid for iATN Premium, then proceeded to get busy with it. Here's what I found when narrowing down my search results to Infiniti J30 cases where all plugs were fouled. (That's the symptom which stuck out the most.)

None of the fixes reported involved the ECT or the MAF, despite them being solid theories. Nor did they involve the FPR's .

The most mentioned fix ( in 3 or 4 cases IIRC) had to do with timing. Either from an improperly set base timing that was retarded too far (the cam sensor on this car is adjustable by hand for setting it) or because of a physically damaged cam gear drive (which engages the "sensor drive".

Craziest cam sensor I've seen. The sensor, pick-up/internal electronics, bearing and shaft are all one piece. It's basically a distributor.. but not really... (the engine is coil over plug ) very weird design. It's official name is the "Crank Angle Sensor". The engine doesn't have cam crank sensor. Just this Crank Angle Sensor. Any theories as to why it's called that?

Anyway, went out, pulled the sensor, inspected the shaft/splines (there were reports that rust damage can cause rounding of the splines & therefore erratic timing). Mine looked good, some old gooey grease, but no rust. So I cleaned it, lubed it, put it back in, then grabbed my timing gun and fire her up.

Long and behold, timing was retarded big time. The mark jumped around a bit between -15 and -20 degrees. This engine should be set at 15 degrees of advance at idle. That may very well explain the so-called "over fueling" and why the cylinders were being washed, causing all the plugs to foul and the raw fuel smoke out the tailpipe. i moved the "crank angle sensor" clockwise to it's travel limit. That got the timing mark where it needed to be at 15 degrees advance and the engine seemed to stabilize ( i really hope it wasn't my imagination).

Sadly, I couldn't run the engine longer than 5 or 10 minutes. My phone was blowing up because my friends were waiting for me to join them for Thanksgiving dinner. So...had to stop everything and clean up for the day.

But Tomorrow I'll pick back and see if she stays stable, and go for a test drive with scan tool in tow. Crossing my fingers.

UPDATE:

Yes, base timing was off, and I adjusted it to spec.
No, it was not the cure. Engine is smooth and consistent when cold, but fuel wash occurs soon after and it chugs horribly and stalls.

All four 02's report full rich when this occurs. I rechecked them for response and they respond accurately to Clear-Flood cranking by leaning out.

Fuel delivery is back on the table again. Given this car's reputation for injector failures, it's possible both banks have a stuck injector or more.

Will test fuel pressure today and report back.

What's the MAF g/s at hot idle with no loads? When it's idling correctly and when it's overfueling. Following the g/s = displacement in liters rule-of-thumb, it should be around 3.0 g/s. For the MAF to be causing a rich condition, the reading will have to be HIGHER than 3.0 g/s. Significantly higher. :lol:

Purge is out IMO, unless there's raw fuel in the canister AND the purge is stuck wide open.

FYI, skip any of the fuel trim PIDs that have B1S1, B2S1, B1S2 and B2S2 in them. Not true fuel trims. Did your Autel not come with the Nissan adapter for OEM data?

Found the 14 pin Nissan Adapter. It was tricky getting into factory mode because the model "J30" doesn't show up n the list under Infiniti. Then, I figured out that you can simply select from a list of modules, and the VCI will cycle through possible protocols till it snags a read on the ECM, BOOM! Getting used to the tool...

Pulled up MAF voltage KOEO and voltage was all over the place. Wouldn't hold a steady line. Then tried to start the car. It was really tough to keep it running and was smoking bad before stalling again. Then unplugged MAF to see what would happen.. car doesn't like that so it wouldn't start.. Then I plugged it back in. MAF Voltage was steady at 200 mv. Wasn't jumping around everywhere.

Car fired right up and idled normally. Test drove car and drove normally. Brought the scanner with me on the drive, MAF voltage was sweeping and returning smoothly with throttle changes.

Wow... the difference between Generic OBD and factory is night and day. The "calculated" MAF value was slow to refresh even when isolated to a single PID.

Thank you Tyler!

Well done getting the OE data to work! Definitely helpful to have access to both OE and Global. Two sides of the same coin.

Pulled up MAF voltage KOEO and voltage was all over the place. Wouldn't hold a steady line.

Really? :huh: Red flag for the MAF. This is where I'd suggest some direct testing at the sensor itself. Either watch the signal on the scanner while wiggling the connector or tapping lightly on the sensor, or get your DMM out and compare what you're seeing on the scanner to actual.

Then unplugged MAF to see what would happen.. car doesn't like that so it wouldn't start.. Then I plugged it back in. MAF Voltage was steady at 200 mv. Wasn't jumping around everywhere.

Car fired right up and idled normally. Test drove car and drove normally. Brought the scanner with me on the drive, MAF voltage was sweeping and returning smoothly with throttle changes.

It's crazy how heavily Nissan/Infiniti products rely on the MAF. :silly: Their backup strategies are very weak compared to other makes. I'd say you disturbed a connection at the MAF when you cycled the connector. That's why it performed well on your subsequent test drive.

Video of MAF being screwy. Was talking to someone else in the vid..

Checked wiring integrity, which checked out. Knocking strictly on the MAF housing was what made it squirm around.

I agree, weak strategy. More than just a weak strategy, its dangerous. It can melt your cats and cause oil contamination.. yikes. I still don't know if the cats survived this ordeal.

Replaced the MAF with a new one. Changed oil&filter and replaced spark plugs. Car is fixed. (Except for possible cat damage now..). Thanks to everyone who chimed in! :woohoo:

Thnk you Master Tyler!

No problem at all. Glad to hear it's fixed! :woohoo: Congrats on the MS908, too. Fantastic scan tool. Do you think this is why the car ended up at auction?

Unfortunately, it's not only the backup strategy that's weak, but the MAF fault detection. Most GM's I've seen would have set a P0101 or P0102 under the same conditions. Not trying to compare GM to Infiniti, necessarily, just noting the difference between makes and how they set codes.

FWIW, I bet the cats survived. Most converters are pretty sturdy, and will take a fair amount of abuse. It's when people drive them around like that for thousands of miles that damage occurs, in my experience.

Also, thanks to you, I now know that the VG30 appeared in cars other than the 300ZX. :silly: Honestly didn't know that before watching your video!

The car was traded in at a local Toyota dealer here in Portland according to the title. But yea.. I've got a feeling they traded the car in (for a pittance if that) because of this issue and how elusive it can be without proper diagnosis. Very likely scenario.

The J30 (known as the Nissan Leopard J Ferie in Japan) is a real oddball of a car. Rear drive mid-size, dense (feels like an ingot), and oddly styled. The Auto was the only trans option. That and it's relative heft is what kept the VG30 from really shining on this model. Otherwise, a neat car.

Thanks on the 908. Got it used for $725 at auction when a local shop closed it's doors.