Fuel problem... still!

[NurseLaura]

Well, last time I was here I had a fuel problem and you all helped immensely! So here I am again, asking for your help again! My 1983 280zx is running very rough (when I can keep her running), and blowing black smoke in rebellion. I have replaced the old nasty fuel tank, the fuel pump. the fuel lines, the fuel filter, and the spark plugs. The mechanic has checked the air flow meter, the O2 sensor, and the fuel rail. The fuel pressure is right in the line (according to the mechanic). Today, the injectors are getting blown clean, but I really don't think that's the problem either. This car has us stumped! Any suggestions? Any input is appreciated. You guys rock!

PS - just a little more info - this is an intermittent problem since I bought the car a few years ago. It will run great for a few thousand miles, then when it goes bad, I replace something and it runs good again. Then just when I think I figured it out this time, the same thing starts happening again. Hmmmm....

[240ZX]

Laura,

My suggestion is to find a good mechanic who is very familiar with the 280ZX and let them assess the problem. Don't take my word for it but, with the EFI cars it's likely just a bad sensor. If it's puffing black smoke, you have a rich condition. A quick look at the plugs can reveal if the problem is local (one cylinder) or across the board (all cylinders). If it's local, it may be a fouled or bad injector and if it's across the board, it may be a bad sensor. Maybe Blake will jump in on this, as he is pretty good with problems on EFI Zs.

Tom

[sblake01]

Well, I believe an 83 would have the E.C.C.S. and I'm not too familiar with that. It's more like a modern system than the 75-82.5 EFI. The advice you give is the direction I'd follow, however. I would have to do some reading to get anywhere near up to speed, as they say, on that system.

[NurseLaura]

Thanks, guys!

Guess I'll have to keep following the "rule out" method. At least I'm learning what's NOT the problem, narrowing down the list of things that COULD BE the problem.

I really appreciate all of your knowledge and input... keep it comin'!

[NurseLaura]

Would you be kind enough to explain the ECCS system to me in a few sentences? I'm familiar with fuel injection in general, and the O2 sensor and stuff, but I don't know about the ECCS.

I know asking questions is the best way to learn about things, even though I may sound ignorant ... and much easier and cheaper than screwing something up!

Thanks again.

[ktm]

As Tom mentioned, the modern EFI car is controlled by sensors more or less. The air flow meter and O2 sensor are only two components. You still have the throttle position sensor, thermotime switch and the cylinder head temperature sensor (CHTS). The CHTS is located on the passenger side of the head between the #5 and #6 cylinders (if I remember correctly). The thermotime switch is located in the thermostat housing. The TPS is located on the side of the throttle body.

The ECCS is just a computer that controls ignition and fueling (basically speaking) based on a series of sensors (knock sensor, CHTS, thermotime, O2 sensor, air flow meter, TPS, etc.). The fuel and ignition maps are programmed into the ECCS. If I remember correctly, the O2 sensor only adjusts fuel in closed-loop mode. It is looking for 14.7:1 and will adjust your fuel accordingly (primarily during cruising/idling).

You say it's puffing black smoke occasionally. Have you run a compression or leak down test? I am not trying to scare you, just trying to rule out other possibilities. If the puff occurs sporadically, good chance that its not piston/ring related.

Does the car smoke when its warmed up and not when its cold? When does it smoke?

[NurseLaura]

It smokes black smoke constantly when it's running crappy, and it's very difficult to keep running. When it first started this latest funk, I could let it warm up a little, then it would suddenly begin running perfectly, and the smoke would stop. Now, I can't even get it to run long enough to warm up, and it's hurtin' when it's running.

Also, I could tell when it was gonna start acting up because it started cutting out during acceleration, and would smoke a little (gray/white smoke). When I would let off the pedal a little, it would kind of "catch up" ya know? However, right now that's not even an issue because I can't even take it on the road at all.

And thanks for the EFI lesson. I don't know what you do for a living, but you should consider teaching mechanics!

[sblake01]

The basic EFI system from 75-82, which I'm familiar with uses an ECU (electronic control unit) which we often refer to as a 'computer' but it isn't. All it does is patch through singnals from the various sensors, switches, etc. It makes no adjustments or computations. From 82.5-83 (84 if you count the Maxima), the ECCS was used. The ECCS (electronic concentrated engine control system) uses a micro-computer. Electrical signals from each sensor are fed into the micro-computer and each actuator is controlled by an electrical pulse with a duration that is computed in the micro-computer. It uses mixture ratio feedback for the closed loop control, a barometric pressure sensor, cylinder head temperature sensor, crank angle sensor, exhaust gas sensor, air temperature sensor, throttle valve switch, air flow meter, battery voltage for memory, and the ignition position start switch to activate it. Considerably different and more complex than the earlier system used in the 75-82. There is a laundry list of things that should be checked based on the symptoms you cited. Do you have a Factory Service Manual? I would be easier to read through it than attempting to post the many pages devoted the maintainence of the ECCS. I have one in .pdf but it's for an 82.

[NurseLaura]

Thanks! I printed out this entire thread and I'm taking it to the mechanic in the AM. Hopefully, between him and you all, and myself, we can figure this thing out. Wish us luck!

[Friar-Tuck]

Nurse L,

My sons 83zx had the same condition after we replaced a head gasket. The heavy smoke and lack of power, seems to be running on two cyls and carbon building up on exhaust tip,was due to the Cylinder Head Temp Sensor located on the Pass side of the engine towards the rear 1/3 of the head just above the block.

(As posted above by KTM )

There are two pin connections in the plug. It looks just like a water temp sensor, plastic cap on brass body.

One of the other guys may have a way to test the loop. I have been trying to find a F.S.M. for under $80.00 :surprised. If you can find one GRAB IT! It would surely help tracking down.... Z gremlins.

Tuck \o/

[sblake01]

You can dowload the 82 FSM which has a section on the ECCS here for free:

(When it's available)

http://carfiche.com/manuals022/cars/

[Rockr69]

Friar -Tuck has it nailed, My 83 maxima (essentially same engine and computer) had same problem. I had accicentally knocked off the plug to the water temp sensor in that exact location and experienced those exact symptoms. Found the hanging plug, put it back on sensor, started car and felt dumb cuz she ran great again. I mean I was happy as well, but I had spent a week trying to figure it out and had to tow it 50 miles home after being stranded cuz it wouldn't run. Oh well live and learn, but I'd check that sensor and plug before spending tons o dough on other things. Here is the link to carfiche http://carfiche.com/manuals022/cars/. They don't have an '83, but I'm pretty sure an '82 is the same. Dan