Help me troubleshoot bucking/stalling (Nistune log included)

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Help me troubleshoot bucking/stalling (Nistune log included)

Post by james92se » Sun Jun 21, 2015 5:17 am

Here's the deal, I'm very sorry this is long but I want to give the total story. I have two VE30DE 5 speed manual Maximas, a 1993 turbo with Nistune, and the other bone stock N/A 1992 model.

A few years back I parked my totally perfectly running N/A Maxima to overhaul it (new steering rack, all new suspension and bushings, all new engine gaskets/seals, brand new coil packs, brand new injectors, brand new knock sensor, brand new knock sensor harness, brand new coolant temp sensor, etc). Unfortunately due to time/money this took me about two years before I actually started driving it again.

I finally finished it up late last summer, and when I first started driving it, it would start to slightly buck as it was being driven. It also stranded me once, which I discovered was because of total cloudly/muddy river water looking gas/gas tank due to sitting for a few years and a clogged fuel filter sock. The gas went bad from sitting for 2 years. I put a brand new fuel pump/sock AND a brand new gas tank in it and a new fuel filter in it.

That said, I still have issues with this car, but I *think* it's separate/different from the bad gas issue. This has absolutely turned into the most frustrating car problem I've dealt with in 15 years of messing with these cars, or any car for that matter:

Despite the new fuel tank/pump/etc, the slight bucking persisted. I can't figure out why, but once the car has been driving for about 15-20 minutes it starts to get a general sense of bucking and stalling. About every other stop light I take off from it gives me bucking/loss of power. Sometimes I'll get a very harsh buck, the type to throw me forward in the seat - when accelerating away from a stop light. Sometimes it's totally fine. When at a steady cruise going 45+ I can feel a very subtle bucking occasionally. When this starts happening, the idle is often very stumbly. If you sit and watch the tach, it'll frequently seem as if the idle is very quickly drug down real low. The needle will instantly drop a few hundred RPM, as if it's being punched downward, then raise back up as the car raises the idle speed. Sometimes, it'll do this over and over until it can just stall itself out if I let it sit there and do it.

It will also stall on me frequently while driving. Sometimes over and over. It will stall on me accelerating from a stop light. It will stall on me cruising down the highway. Sometimes it just turns off, sometimes it's accompanied by bucking. When it stalls on me, it almost always starts right back up. I just put it into neutral and start it back up (even cruising down the highway). About 70% of the time it comes back on 1st try. The rest of the time it takes multiple tries to get it to fire back up, as it doesn't want to "catch" and run the first try. This is especially annoying when it happens to me taking off from an intersection with pissed off people behind me.

An interesting quirk is that it's much more frequent/consistent when I have the AC on. However, even with the AC off it still happens - it just happens MORE when the compressor is engaged. And again, this typically only starts to happen once the car has been driven for 15-20 minutes. My commute to work is only 10 minutes, so 90% of the time, it drives FLAWLESSLY on my way to work. But it has bucked/stalled on me a few times even when the engine is cool/not up to operating temp. When I go out for lunch, or if I do an errand after work and end up driving 15-20 minutes continuously, that's when it almost without fail starts doing its crap.

Having said all that, here is everything I've done to try to figure this out/fix it (as stated above it has a new fuel pump, fuel pump sock, and fuel filter):

- NO ECU fault codes
- Bypassed knock sensor with resistor
- Swapped ECU's
- Installed Factory basemap on my Nistune ECU, could tell no discernible issues watching the CONSULT readouts on Nistune even when the engine was stumbly
- Replaced fuel pressure regulator with brand new unit
- Swapped ENG CONT relay from my other Maxima
- Swapped IGN COIL relay from my other Maxima
- Replaced TPS with brand new unit
- Replaced CPS (crank position sensor) with brand new unit
- Swapped my OLD coil packs back in to replace the brand new coil packs
- Replaced power transistor unit with brand new unit
- Swapped MAF with known good unit
- Swapped coolant temp sensor from my other Maxima
- Swapped the OLD injectors back in (thought maybe the bad gas clogged them)
- Swapped the EGR with from my other Maxima
- Swapped the oxygen sensor from my other Maxima
- Rechecked/replaced all vacuum hoses
- Pinched blow-by hose, did not raise idle speed (indicates no IM leak per FSM)
- Plugged vacuum/vent hoses as test - no change
- Tested fuel pressure - idle pressure is exactly 35 PSI. Generally between 32-40 PSI driving around the neighborhood (residential streets, so not much more than about 30 mph). Fuel pressure definitely never cuts out or bounces around. It's all very smooth. Even taped the fuel pressure gauge to my windshield and drove it around - pressure was nearly 40 PSI literally the moment it stalled on me
- Swapped ENTIRE ENGINE HARNESS from my turbo Maxima
- Added grounding kit
- Inspected intake manifold gasket for leaks/problems during injector swap
- Inspected new fuel pump/sock for indications of muddy gas/clogged sock (no indication)
- Even did the old remove-the-gas-cap in case of fuel vapor lock trick

I have had many people suggest to me that the "timing is off" or that it has bad valves etc. I never removed the heads during the overhaul and highly doubt bad valves or any internal damage seeing as the car drives exceptionally sometimes. No smoking or anything either. And regarding the timing, I let it warm up today, and played with my CPS (how you adjust the timing on the VE30), and basically any position I set it in, it still had the same goofyness at idle. Severely retarded or severely advanced, same sort of stumbling. So I don't believe it's a timing issue.

All that said, here's where I really hope somebody here can help me (hoping some datlogging will help to figure out what the cause of my issues are):

I let the car get up to temp today and let it run at idle while it was acting mildly goofy. I made a Nistune log (after I set the timing back to stock). Here's the one minute video of what it was doing. You can see via the tach what it was doing. It never stalled here, but this is a sort of mild version of the annoyingness I'm dealing with. I didn't drive it during this log, but I guarantee if I had driven it, it would have stalled on me numerous times.

Here's a link to the Nistune log. I started my video and the log at the same time, but I can't say they're EXACTLY timed together. They should be nearly identical though, not that it matters. All I can see meaningful from the log is that when the idle drops down into the 600's, the timing shoots up to mid 20's, which seems like a normal response to try to kick the engine back up: ... sp=sharing

And of course open to any other ideas here. This car is driving me insane. I wish now I had never overhauled it. The ironic thing is I bought so much crap new (injectors, coil packs, etc.) specifically so that I wouldn't have to deal with any problems from this car. Boy was I wrong. Thanks in advance for any ideas/help/tips.

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