sherm@drune.UUCP (ShermanSP) (01/28/85)
I am having an intermittent problem with my 280ZX's fuel injection system, and thought I'd go to then net for some additional expertise/advice. (For those not familiar with the Z's system, it is a basic Bosch electronic fuel injection system; similar to the ones in Volvo's and the older VW's). The problem is this: Every so often the engine will idle very poorly; barely making it at about 500 rpm, as opposed to the usual 750-800 rpm. The problem is definitely worse (i.e. more frequent) during warm-ups in cold weather. But it occassionally happens after the engine is fully warmed-up. Most of the time when it's happening, it will go away at an engine temp of about 130F. I have the shop manual, and have tried/tested a variety of fuel system components. Since it seems to be tied to the warm-up period, I first suspected the "choke" circuit. The air valve and auxilary fuel valve seem to be OK though, (although with an intermittent problem I may just have been lucky/unlucky when I was testing them.) Raising the idle speed doesn't eliminate the problem. The engine will still do its low speed thing every so often, just at a slightly higher RPM (note not much higher rpm). I am now at the point where (without more advice) I would probably begin testing all of the fuel system components. Since I don't really want to go on a wild goose chase, and I REFUSE to go to a garage, where they will replace components one by one til they "luck" onto the problem, I am hoping that someone out there in netland has had or heard of this problem before. Please send advice, hints and/or guesses to the net or email. Thanx in advance. ...!ihnp4!drune!sherm (303) 538-4704
notes@harpo.UUCP (01/29/85)
I had a similar problem with a 280z that turned out to be a loose connection to the fuel pump. When the engine started running the vibration was enough to maintain the connection. It was detected by running the fuel pump with the oil pressure sender disconnected; this allows the fuel pump to run with the engine off. Turn the ingition to on but don't start the engine and the pump should run. BTW, I presume you've checked the "thermotime" switch.
rex@eneevax.UUCP (Rex Root) (01/31/85)
The symptoms you discribe indicate one of two devices
not working properly:
The water temperature sensor (which I would immediatly
suspect, if the engine has ever overheated. (It may
have suffered damage as a result of getting too hot)
The air temperature sensor ... less likely.
I assume you have the DATSUN 280ZX manual .. It gives the
resistance (in ohms) of each of these devices for various
temps.
Make sure all of the vacuum lines are intact and be sure
there is a good seal on the oil filler cap ... the engine
will not idle smoothly if there is a vacuum leak. The
crankcase and upper valve area MUST be at a vacuum.
If these checks fail I would suggest doing a swap of
the control unit from another ZX of the SAME year.
If it comes to that, be sure to disconnect the battery
before doing the transplant.
You mentioned the Auxilary Fuel Valve .. better known
as the COLD START VALVE, (enrichening jet) ... This
is NOT the problem ... The cold start valve is ONLY
open during start-up. ie: when the key is in the
start position.
Keep me posted ... I'm still thinking.
Rex