erratic behavior, stalling, spontaneous acceleration

DDA

Hey guys, thanks for going over my message! I’m experiencing the following problem(s) with my 2010 370Z for multiple years now:

- Engine is revving stationary perfectly, yet takes a dip every ten seconds or so (to the point of stalling even); it can do this indefinitely or multiple times, before it finally finds the correct settings. Unfortunately, at the next traffic light or the next day (or after a short stop at the butcher or baker) usually the problem is there again. Engine software doesn't seem to find or remember the correct operating values. (ECU?)
- Sometimes it happens that when I accelerate, departing from a standstill, the engine rpm’s don’t stop increasing until I take my foot off the pedal?! I press my throttle pedal around 10% or so, to take off gently, yet the engine's rpm continue to steadily climb up all the way to redline! Once I lift my foot off the pedal, the revving starts to correspond with the throttle input again. (Throttle pedal error?)
- Occasionally, after coasting (be it in gear or not), when trying to re-accelerate again, the engine does this with a noticeable boost/bump at first, only to experience a little dip immediately after. Like it's trying to compensate, or is wrongly configured. Makes it impossible to shift smoothly. Usually (but not only) this happens while accelerating out of a turn, making one of the rear wheels lose traction for a split second even! Esp light comes on briefly. (VVEL?)
- I can feel some vibrations in all of the car (but gear stick mainly) while decelerating in gear from around 4000 to 3000 rpm (approx). Usually this is accompanied by a few dampened "explosive sounds" in the exhaust. Don’t know the exact word to describe this, but it's nothing dramatic. Very silent. Very muffled. Sounds sporty, yes, but since it's not doing this every time, I'm guessing it's not normal. (Unburnt fuel arriving in the exhaust?)
- When starting with a cold engine, there's a very noticeable rpm drop (+/-400) the exact moment the engine hits its normal operating temperature. Precisely when the led for the water temperature reaches the middle. This is most likely to the choke stopping its operation, so could be perfectly normal though, yet never noticed this in any other car I ever drove. Might just be me though.

Before I give any more details:

- This started happening shortly after I had an LPG (Liquid Propane Gas) installation installed, so most likely this has something to do with it. Did the guy who did the installation damage a part during the process, or is there a certain incompatibility, no idea.
- Engine stalling problem is worse on the standard/regular fuel (I mean 98 of course), compared to the LPG fuel, cause while running on LPG the engine never fully stalls, only takes a dip but is able to recover just in time each time.
- Nissan is blaming it on the LPG installation (yet many cars drive around perfectly using this system), while the LPG guy is of course saying the problem is with Nissan, since his software only copies what Nissan software does. He says, if the problem is happening while not on LPG, then should fix it there first.
- Two Nissan garages have looked at the problem, yet are unable to find anything via their computer diagnostics. The guy of the LPG installation examined the car, but found nothing wrong with it.
- I do have a check engine light, but the error code (p0420) refers to my fried catalytic converters (caused by running hotter on LPG compared to 98 octane fuel). Occasionally there’s a code in there for a misfire in cylinder x.
- Tried resetting loads of things, did pedal dance multiple times, and recently a reset of the valves in the throttle body (gasklephuis in Dutch) seemed to do the trick, but there were some small issue still. After doing the pedal dance again, problem is as bad as it ever was. Might do a valve reset again, and see how it lasts.
- Spark plugs changed for LPG compatible ones.
- Drove several hundreds of km's without the use of the LPG system, so the engine software would have enough time to calibrate, yet to no avail.
- Catalytic converters upgraded to Z1 racing type, yet fried in no time as well.
- Nissan is giving me all sorts of horror stories about their cars and LPG systems, yet I did well over 80000km by now, with all of the problems mentioned above; doesn't seem to get worse, doesn't improve either unfortunately.

In brief, what faulty part could be the reason that the factory software/hardware is unable to fine tune and/or finalize the engine settings? At the same time, there are days the car drives near perfect, with none of the problems above! If there’s something truly broken (mechanically/physically), could it ever do that then?

Regards

Didier

Rusty

You had no issues before the install of the LPG. Then got issues after the install. Sounds like a plug connection, bad wiring. We don't do the LPG conversion here in the states much. Mostly on rock buggies. Never seen one on a Z.

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