76Datsun280z Posted April 22, 2007 Share Posted April 22, 2007 My stock '76 280z is running on the rich side. I start it up when it's cold in the morning, it will always leave a black spot on in the garage or in the driveway from under the tailpipe which is telling me it's running rich and also the poor mpg. Is there something in the AFM that I can dial back to lean the mixture out with? Thanks. Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 22, 2007 Share Posted April 22, 2007 step one: clean the connector to your Coolant Temperature Sensor. step two: check the adjustment of your throttle position sensor. (and connector) between the two of them, they account for many many stock Z-cars presenting the "running rich" complaint. this link should help, its Blue's techtips page for the FI system. download, print, and staple to your forehead a copy of the Datsun EFI bible; it is an invaluable resource. Quote Link to comment Share on other sites More sharing options...
Overkill Z Posted April 22, 2007 Share Posted April 22, 2007 on the bottem of the airflow meter..towards the back of it..on the drivers side of it there is a screw that if u turn clockwise it will lean up the mixture Quote Link to comment Share on other sites More sharing options...
Overkill Z Posted April 22, 2007 Share Posted April 22, 2007 or is counter clockwise...lol Quote Link to comment Share on other sites More sharing options...
76Datsun280z Posted April 23, 2007 Author Share Posted April 23, 2007 Thanks for the help guys! Greatly appreciated! I turned that screw to the left to lean it out roughly half a turn and I'll see if that makes any difference. Quote Link to comment Share on other sites More sharing options...
Phantom Posted April 25, 2007 Share Posted April 25, 2007 Be advised that the two 2-wire sensors at your thermostat housing can cause a lot of your running rich problem. They are your Thermotine switch and the engine temperature for the ECU. Disconnect the wiring harness at the sensors - manually scrape the contacts clean, coat them with dielectric grease and then re-assemble. THEN - follow the leads from the sensors about 16-18" toward the main wiring harness. If you look/feel carefully you'll find a lump in the wiring. Strip away the insulation there and you'll find some wonderful little corroded aluminum bullet connectors. Clean them the same way and your running rich will disappear. Then you can set screw on your airflow meter back to where it belongs. Also - you may want to pull your plugs and clean them as they may be getting fuel fouled by now. Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 25, 2007 Share Posted April 25, 2007 Be advised that the two 2-wire sensors at your thermostat housing can cause a lot of your running rich problem. They are your Thermotine switch and the engine temperature for the ECU. Disconnect the wiring harness at the sensors - manually scrape the contacts clean, coat them with dielectric grease and then re-assemble. THEN - follow the leads from the sensors about 16-18" toward the main wiring harness. If you look/feel carefully you'll find a lump in the wiring. Strip away the insulation there and you'll find some wonderful little corroded aluminum bullet connectors. Clean them the same way and your running rich will disappear. Then you can set screw on your airflow meter back to where it belongs. Also - you may want to pull your plugs and clean them as they may be getting fuel fouled by now. and if THAT does not fix it, go to the tech tips page and read about your throttle position sensor. the engine temperature of the ecu sensor is the CTS (coolant temperature sensor) I mentioned before. Just turning the screw is almost certainly nothing more than covering up your problem, which is very very likely to be corrosion in these contacts or improper function of these sensors. Once they are confirmed to be operating properly, THEN you adjust the idle air mixture on the TB. The screw does NOTHING more than control air flow at idle, when the AFM flapper is essentially shut. Go download the EFI bible and read it through.. it explains in clear english how the entire FI system works, and it really is FANTASTICALLY simple. Quote Link to comment Share on other sites More sharing options...
76Datsun280z Posted April 25, 2007 Author Share Posted April 25, 2007 Thanks for the help guys! I'll have to try that! Quote Link to comment Share on other sites More sharing options...
mom'sZ Posted April 25, 2007 Share Posted April 25, 2007 First.. as Daeron later in the thread states, this on the bottem of the airflow meter..towards the back of it..on the drivers side of it there is a screw that if u turn clockwise it will lean up the mixture is wrong. That screw is the idle speed adjustment. It allows you to set the idle speed (RPMs) and doesn't effect mixture at all Then this... Be advised that the two 2-wire sensors at your thermostat housing can cause a lot of your running rich problem. They are your Thermotine switch and the engine temperature for the ECU. Is only partially true. The thermotime switch only controls how long the cold start valve can operate. The cold start valve provides extra fuel on cold starting and the thermotime switch cuts it off after a given period of time so the engine doesn't flood. The thermotime switch therefore can only effect mixture at cold start up (maybe that's what Phantom meant)The water temp sensor on the otherhand is very important for fuel mixture, both on start up and while running at normal temp. Phantom's suggestion to clean the connectors to these sensors is a very good one. Daeron also gives some good advise and if THAT does not fix it, go to the tech tips page and read about your throttle position sensor. Although the throttle position sensor on a 76 isn't really a sensor. It's two contact switches. One set of contacts tells the ECU he is at idle. The other tells the ECU he is at a large throttle opening state. If you pop off the cover on the throttle position sensor you will see two little sets of contact points. A guy who was a nissan tech back when the 280 was a current model showed me how to adjust it. You adjust it by (gently) bending the contact point arms. (if adjustment needs to be made) He told me it was real common for them to end up both touching at once and that was bad. Work the throttle as you adjust, make the first set touch just as the throttle is completly closed. Make the second set touch when you get the throttle almost fully open, (maybe around three quarters of the way open) Allow some travel in the middle where neither touch and make sure they don't touch at the same time. I think the connections to your water temp sensor are corroded or the water tempature sensor itself is bad. It's been my experience that when it goes bad, the ECU goes full rich. The car will barely run, smoke badly and not idle. If you clean the connections and that doesn't help, replace the sensor, it's only 15 bucks and available at any auto parts store. There is an adjustment to change the mixture. It involves opening up the air flow meter. Here's a link to a member of the Texas Zcar club's tips on doing it. He's known as Blue on the Zcar.com forum. http://www.atlanticz.ca/zclub/techtips/afm/index.html Here is a link to the fuel injection bible http://www.atlanticz.ca/zclub/techtips/efisystem/280zfuelinjectionbook.pdf Download it, print it out, read it, learn it, rinse, repeat It gives procedures for testing and adjusting all these components. How to check the sensor outputs at the connector to the ECU to see what signal the ECU is truely getting using a common multimeter. Good luck Quote Link to comment Share on other sites More sharing options...
76Datsun280z Posted April 27, 2007 Author Share Posted April 27, 2007 is wrong. That screw is the idle speed adjustment. It allows you to set the idle speed (RPMs) and doesn't effect mixture at all Thanks for the info, that screw you are mentioning is not the idle speed adjustment screw for the rpm. That screw is to adjust the rich/leaness of when the engine is at idle. Quote Link to comment Share on other sites More sharing options...
Daeron Posted April 28, 2007 Share Posted April 28, 2007 Thanks for the info, that screw you are mentioning is not the idle speed adjustment screw for the rpm. That screw is to adjust the rich/leaness of when the engine is at idle. Yah, thats what I said.. essentially. The idle SPEED screw is the largish one towards the top.. BUT the point remains, neither of them has any effect on anything other than idling conditions... Quote Link to comment Share on other sites More sharing options...
76Datsun280z Posted June 3, 2007 Author Share Posted June 3, 2007 Thanks guys, it seems to "load up" when you punch it or get into the high rpm's around say 3500. When this happens, it will load up and jurk because it's getting to much fuel and blow a big cloud of smoke out the back. Could this be timing? I'm thinking it could also be the head temperature sensor staying open causing the rich mixture. Thanks again for the comments. Quote Link to comment Share on other sites More sharing options...
76Datsun280z Posted June 4, 2007 Author Share Posted June 4, 2007 I tested my thermotime switch and my head temperature sensor and both check out fine and working. Also checked my coldstart valve to see if it was leaking and is not. I ended up adjusting my afm and it seems to run a lot better (leaner). It was all out of adjustment because when my dad was adjusting when we put the new engine in it ( didn't know what he was doing) so I think that was the culprit. Thanks again!! Quote Link to comment Share on other sites More sharing options...
Daeron Posted June 5, 2007 Share Posted June 5, 2007 Are you beginning to see how it all operates in general? its a pretty simple system. That EFI bible is the single most important sixty pages for a 280Z owner to have access to; between the hardware and the manual, the Fuel Injestion system make the carbs totally obsolete, in terms of stock performance and reliability. Quote Link to comment Share on other sites More sharing options...
76Datsun280z Posted June 5, 2007 Author Share Posted June 5, 2007 Yup, it's all pretty simple and easy to understand after to you get to know the EFI bible. Quote Link to comment Share on other sites More sharing options...
kastmaster Posted June 25, 2007 Share Posted June 25, 2007 I'm having this problem of running rich on my '80 280zx non-turbo. I suspect that it's been running rich for at least several months. Is it true that you can (partially) smell when it's running rich? I always thought it had a more "saturated" or "sweet-like" smell to the exhaust...I dunno lol. Great thread! (sorry bout reviving this thread from the dead) Quote Link to comment Share on other sites More sharing options...
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