andy280zxt Posted May 13, 2010 Share Posted May 13, 2010 So i would love some suggestions on what might be causing my 83 280zxt to run so rich. When i give the car half throttle or more it starts to sputter and will smoke black from the exhaust, when its sputtering it usually doesnt want to go above 2 or 3k rpm. but once it gets to about 3-3.5 it'll start pulling again with minor setbacks. ive replaced spark plugs, fuel and air filter, and the 02 sensor since i bought the car 2 weeks ago. the PO said the car had bad gas in the tank and thats what was causing it to run so shisty, but i dropped and cleaned the tank and it didn't seem to make much of an improvment. If you could leave me some tips on what it might be it would be much appreciated. thanks everyone in advance.. Quote Link to comment Share on other sites More sharing options...
JSM Posted May 13, 2010 Share Posted May 13, 2010 Some interesting reading that may get you down the right path: http://forums.hybridz.org/index.php?/topic/65944-1978-280z-fuel-problems/page__p__619773__hl__rich%20tempature__fromsearch__1entry619773 http://forums.hybridz.org/index.php?/topic/55371-76-280z-running-rich/page__p__503089__hl__rich%20tempature__fromsearch__1entry503089 Quote Link to comment Share on other sites More sharing options...
roger.svoboda Posted May 13, 2010 Share Posted May 13, 2010 Check out the afm per the manual or FI bible. CHTS might also cause that issue. Continuously leaking or stuck open injector would do it. Put a fuel pressure gage in the circuit to the rail watch the pressure after you turn off the engine. If it falls off rapidly could be a stuck injector. If the fuel pressure is abnormally high the fpr might be at fault. the injectors are designed to deliver a metered quantity of fuel but the pressure on the fuel rail must be correct. Too high Too much fuel. Too low not enough fuel. Quote Link to comment Share on other sites More sharing options...
andy280zxt Posted May 13, 2010 Author Share Posted May 13, 2010 Check out the afm per the manual or FI bible. CHTS might also cause that issue. Continuously leaking or stuck open injector would do it. Put a fuel pressure gage in the circuit to the rail watch the pressure after you turn off the engine. If it falls off rapidly could be a stuck injector. If the fuel pressure is abnormally high the fpr might be at fault. the injectors are designed to deliver a metered quantity of fuel but the pressure on the fuel rail must be correct. Too high Too much fuel. Too low not enough fuel. Thankyou both for your suggestions, i was just going to add to this post that my water temp sensor has not been connected since i got the car.. i'm assuming this is my problem although i have not yet checked i will do that tomorrow. i am not sure if my CHTS is working or not although it is connected and looks to be in good condition, wires and all. I also wanted to add that i do not have a dropping resistor..would this effect the way my car runs? Quote Link to comment Share on other sites More sharing options...
andy280zxt Posted May 13, 2010 Author Share Posted May 13, 2010 Some interesting reading that may get you down the right path: http://forums.hybridz.org/index.php?/topic/65944-1978-280z-fuel-problems/page__p__619773__hl__rich%20tempature__fromsearch__1entry619773 http://forums.hybridz.org/index.php?/topic/55371-76-280z-running-rich/page__p__503089__hl__rich%20tempature__fromsearch__1entry503089 Thanks JSM.. i tried searching the thread for "running rich" but didn't find anything, i appreciated you taking the time to forward those links Quote Link to comment Share on other sites More sharing options...
roger.svoboda Posted May 13, 2010 Share Posted May 13, 2010 water temp sensor only affects the gage reading no input to the ecu. you can check chts with vom see manual. most likely in my mind - Leaking injector or fuel pressure too high. Chts problems usually manifest some degree of change as the engine warms up. O2 Sensor bad can also make it run rich. Quote Link to comment Share on other sites More sharing options...
andy280zxt Posted May 13, 2010 Author Share Posted May 13, 2010 water temp sensor only affects the gage reading no input to the ecu. you can check chts with vom see manual. most likely in my mind - Leaking injector or fuel pressure too high. Chts problems usually manifest some degree of change as the engine warms up. O2 Sensor bad can also make it run rich. What about the thermotime switch? will that cause my car to run rich?..... i have quite a few sensors missing or broken on this car i believe. i dont even know where to begin Quote Link to comment Share on other sites More sharing options...
19762802+2 Posted May 13, 2010 Share Posted May 13, 2010 (edited) You need to take a day and read through the EFI bible and go over how it all works and then the next day Go look over your car while referring to the EFI bible. Test everything even if you don't think it is important it will save you grief later, and once you establish what is wrong replace it if you need too don't rush take your time. If have any questions after reading the EFI bible just come back here and ask and we will do what we can. EDIT: Misinformation about the Thermotime switch, Didn't notice it was a turbo. Edited May 13, 2010 by 19752802+2 Quote Link to comment Share on other sites More sharing options...
andy280zxt Posted May 13, 2010 Author Share Posted May 13, 2010 Yes if the thermotime switch didn't work right it could make your Cold start injector go off all the time. You need to take a day and read through the EFI bible and go over how it all works and then the next day Go look over your car while referring to the EFI bible. Test everything even if you don't think it is important it will save you grief later, and once you establish what is wrong replace it if you need too don't rush take your time. If have any questions after reading the EFI bible just come back here and ask and we will do what we can. Ok that makes sense.. i was just reading through the manual though and it shows that my 1983 turbo model doesn't come with a thermotime switch or a cold start valve(i could not find the valve anyway,nor could i find a plugged hole where it went) it also says that my car doesnt have a water temp sensor, only the cylinder head temp sensor (which i replaced and could tell no difference in the way my car ran) i appreciate your advise and i will take the time to read over the efi bible again. since i replaced the sensor with no luck, my next attempt will be to check the injectors Quote Link to comment Share on other sites More sharing options...
roger.svoboda Posted May 13, 2010 Share Posted May 13, 2010 there is no cold start injector on turbo cars. Find a test for the O2 sensor if you can otherwise just replace it. Bad one will cause rich running. Pull off the connector see if you notice any diffference in running. rig you can use to check fuel pressure under $15. i'd start there then go to the O2 sensor. Quote Link to comment Share on other sites More sharing options...
19762802+2 Posted May 13, 2010 Share Posted May 13, 2010 there is no cold start injector on turbo cars. Find a test for the O2 sensor if you can otherwise just replace it. Bad one will cause rich running. Pull off the connector see if you notice any diffference in running. rig you can use to check fuel pressure under $15. i'd start there then go to the O2 sensor. My bad, I edited my post thanks for the heads up. Quote Link to comment Share on other sites More sharing options...
andy280zxt Posted May 14, 2010 Author Share Posted May 14, 2010 so i checked the fuel pressure and its running at around 30 lbs while idling, i shut off my car and the pressure only dropped about 1 lb and sat there for a while, so i believe my injectors are still good. I replaced the o2 sensor about a week and a half ago and could tell little improvement. i bought a new chts and replaced the old one and could tell no difference in the way my car was running.. any other suggestions possibly? Quote Link to comment Share on other sites More sharing options...
roger.svoboda Posted May 14, 2010 Share Posted May 14, 2010 next question then is how do you know it is running rich? You would need some sort of justification to state that it is running rich. The obvious stuff you've done so that leaves the afm. Do a search there are many posts on diddling it. Quote Link to comment Share on other sites More sharing options...
andy280zxt Posted May 14, 2010 Author Share Posted May 14, 2010 next question then is how do you know it is running rich? You would need some sort of justification to state that it is running rich. The obvious stuff you've done so that leaves the afm. Do a search there are many posts on diddling it. well, my only real justification is that it is smoking black.. (that is a good indication of a rich full mixture isn't it? or am i wrong?) also it will backfire fairly often when starting it up normally, or after it dies. I did a visual inspection of the AFM and the flap inside seems to be moving smoothly.. i will look to find out how else to check my afm Quote Link to comment Share on other sites More sharing options...
roger.svoboda Posted May 14, 2010 Share Posted May 14, 2010 smoking black sure sounds like rich. From what you have done the afm is what is left. It is apparently telling the ecu that far more air is going to the engine than is therefore getting fuel for air that isn't there. Do search on that you can turn it slightly and change the signal to the ecu to make it seem like more or less air. Search posts on changing the afm there are plenty. Just heed all the words of caution. If you let it unwind you may never get it back together. If you got a junkyard near by might find a used one to use for a comparison. Quote Link to comment Share on other sites More sharing options...
andy280zxt Posted May 15, 2010 Author Share Posted May 15, 2010 smoking black sure sounds like rich. From what you have done the afm is what is left. It is apparently telling the ecu that far more air is going to the engine than is therefore getting fuel for air that isn't there. Do search on that you can turn it slightly and change the signal to the ecu to make it seem like more or less air. Search posts on changing the afm there are plenty. Just heed all the words of caution. If you let it unwind you may never get it back together. If you got a junkyard near by might find a used one to use for a comparison. alright, so i did some testing on my afm following the haynes manual procedure and apparently it is faulty. Anybody have a working MAF for sale?? Quote Link to comment Share on other sites More sharing options...
roger.svoboda Posted May 16, 2010 Share Posted May 16, 2010 you don't want a maf they are used on the z31. you want an air flow meter which is what they used on s130 Quote Link to comment Share on other sites More sharing options...
andy280zxt Posted May 17, 2010 Author Share Posted May 17, 2010 you don't want a maf they are used on the z31. you want an air flow meter which is what they used on s130 Thank you roger, Im pretty sure my afm is bad but not positive. now when i accelerate my car hesitates up to 2k rpm and then loses all power and starts sputtering violently.. i was told this is a sure sign that i have a bad afm, is this true? I am just want to be positive this is my problem before i go throwing money and parts i dont need. is there any way it could have something to do with my ecu or wire harness? Quote Link to comment Share on other sites More sharing options...
roger.svoboda Posted May 17, 2010 Share Posted May 17, 2010 anything is possible ask Apollo 13. go with the most likely not the twilight zone solution. Ask around if you got a local z club might find someone wiling to loan or sell you one that works. I don't like to just replace parts either but sometimes you have to gather data and then make the educated guess and go with the most likely. Quote Link to comment Share on other sites More sharing options...
Daphur280 Posted August 18, 2010 Share Posted August 18, 2010 Check out the afm per the manual or FI bible. CHTS might also cause that issue. Continuously leaking or stuck open injector would do it. Put a fuel pressure gage in the circuit to the rail watch the pressure after you turn off the engine. If it falls off rapidly could be a stuck injector. If the fuel pressure is abnormally high the fpr might be at fault. the injectors are designed to deliver a metered quantity of fuel but the pressure on the fuel rail must be correct. Too high Too much fuel. Too low not enough fuel. How would you narrow down to which injector would be the culprit were it stuck open? Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.