rickyellow zee Posted May 25, 2016 Share Posted May 25, 2016 Car is 78 280Z with 83 L28ET. The car starts no problem and runs fine but under WOT its rich according to my narrow band air fuel gauge and the black poofs of smoke when I get on it hard. That and poor gas mileage. I figure its the CHTS so I did the tests as per the FSM and everything checks out. I recently cleaned up the CHTS wiring as it was old and needed attention. So when the engine is cold I unplugged the CHTS plug and no difference at all in operation. I then jumped the CHTS plug with a paperclip and still no change. TonyD once said that doing this should trick the ECM into thinking that the car is cold and go rich. Nothing... I took it for a rip to heat it up and checked to see if the ECU's LED was blinking indicating the 02 sensor is working. I then unplugged the CHTS when warmed up and still no change at all in the idle. I read that when the CHTS is unplugged the car should bog out due to too much fuel. Mine does not. It appears that the CHTS and ECM are not communicating. At least that's what I think. Any input or other tests I could try to correct the rich condition at WOT. Thanks Rick Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 25, 2016 Share Posted May 25, 2016 Test the CHTS pins at the ECU connector. Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 25, 2016 Author Share Posted May 25, 2016 Did just that. Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 25, 2016 Author Share Posted May 25, 2016 I may open the ecu and test from inside? Not sure if this can be done. Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 25, 2016 Share Posted May 25, 2016 Did just that. What numbers did you get? Did you get an open circuit when you disconnected the CHTS? Do the resistance numbers match the chart? Are you testing the right pins, 1983 ECCS? The answer's in the details. "Did it" isn't enough. Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 25, 2016 Share Posted May 25, 2016 There are a couple of bullet connectors in between the CHTS and the computer. Could be dirty or shorted. That's why the numbers are needed. Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 25, 2016 Author Share Posted May 25, 2016 The resistance numbers matched the chart when tested at the ecu and sensor so I guess that rules out the wiring. .03 ohms at 80C. 1983 ECCS and yes I was testing the right pins(23 26). I did not test with the CHTS disconnected. Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 25, 2016 Author Share Posted May 25, 2016 (edited) What to test next? Edited May 25, 2016 by rickyellow zee Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 25, 2016 Share Posted May 25, 2016 How about FPR performance? Missing vaccum hose maybe, or connected to wrong source. Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 25, 2016 Author Share Posted May 25, 2016 The fpr I tested a while back. Don't remember the numbers but I do remember it was in spec. The vacuum hose is new. I had replaced the exhaust/intake gasket recently and replaced all vaccum lines, all injector plugs and cleaned up any wiring on the injector side that needed TLC. Just trying to get this ol girl healthy. Still dont know why the CHTS makes no difference if its plugged in or not. That HAS to mean something. Thanks Quote Link to comment Share on other sites More sharing options...
seattlejester Posted May 25, 2016 Share Posted May 25, 2016 Is your car modified? Running more boost? I would be tempted to throw a wide band in there at least just for the gauge, narrow bands have a pretty narrow range it would be nice to know if you are running an AFR of 12 or 10. Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 25, 2016 Author Share Posted May 25, 2016 The car is stock except for a muffler and boost is at 11 lbs.I know its not the most accurate gauge but it gets you in the ballpark. Right now when I go WOT it goes almost full rich. The car is fine at partial throttle with the gauge reading Stoichiometric. If I could only lean out WOT and leave idle and partial throttle alone. I know you can adjust the AFM but that leans out the whole curve. Not so good. Quote Link to comment Share on other sites More sharing options...
seattlejester Posted May 26, 2016 Share Posted May 26, 2016 Full rich on a narrow band gauge can mean anything from 10.3-14.5 AFR. The tail end of the voltage is all compressed. You should not be using a narrow band AFR gauge to tune your car. It is not in the right ball park you are using stadium lengths to try and measure yard increments. You should not be aiming for stoich at WOT. That is really really a bad idea. Please read up on AFR and narrow vs wide band. Look up charts and see why it is a bad idea. Quote Link to comment Share on other sites More sharing options...
NewZed Posted May 26, 2016 Share Posted May 26, 2016 You do have some odd things going on. But, as noted, the narrow band O2 sensor is only really useful for the ECU to use at cruising conditions, to trim the injector open times. It's useless as a gauge, it only shows three states - lean, stoichiometric and rich. You can't see "full rich" on a narrow band O2 sensor. It's not in the the ball park. So that leaves puffs of black smoke, "poor" mileage, and the lack of response to the CHTS sensor. An actual mileage number might remove that one, leaving just two things that may or may not matter. Numbers, numbers, numbers. Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 26, 2016 Author Share Posted May 26, 2016 (edited) Full rich on a narrow band gauge can mean anything from 10.3-14.5 AFR. The tail end of the voltage is all compressed. You should not be using a narrow band AFR gauge to tune your car. It is not in the right ball park you are using stadium lengths to try and measure yard increments. You should not be aiming for stoich at WOT. That is really really a bad idea. Please read up on AFR and narrow vs wide band. Look up charts and see why it is a bad idea. Edited May 26, 2016 by rickyellow zee Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 26, 2016 Author Share Posted May 26, 2016 m not using the narrow band to tune my car. lol. Just so you know Ive been driving turbo charged cars for over 20 years now and I get it, have had my other car (CRX) tuned multiple times. I know what im talking about for the most part. Cool? No punk kid here. Im a guy well into his 40's. lol. Now my narrow gauge has served me well in the past. I know its no replacement for a wide band and it cannot be trusted for tuning purposes but it does give me some sort of idea of where my air fuel is at. Its not fully pegged to the right indicating full rich so I have an idea where my tune is at. Also I never said I wanted to be stoich for WOT. I get it again!!! A little richness is a goood thing. Lowers temps etc. Safety!! YES!! My CRX has been boosted for over a decade making 235 to the wheels on a 1.6 D series. This motor made 110hp at the most stock. This is cause I know what Im doing. Know when to have it tuned when I increase boost., add a mod ETC. Know how to read my various gauges. Datsuns and the L series are relatively new to me and I appreciate the help that you guys offer. Thanks for that... Thats why Im here. Ive had quite a few rude smart ass answers here but you get that on forums. har har. Now I have no numbers numbers numbers to give yall regarding mileage. The car is a weekend cruiser and I top up the tank when its low. Cant tell you how many MPG. Dont know where to go from here....more tests. Yay! Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 26, 2016 Author Share Posted May 26, 2016 (edited) More tests... I get continuity when I plug my multimeter into the CHTS plugs ground and the other end to the engine harness ground. This tells me that the ground is good. I used the ohm meter and I get 0 which is excellent. Its going from the CHTS plug through the ECU, out the harness to the grounds that attach to the engine. Everything seems good there. Took the casing off the ECU and tested the CHTS at the pins inside and I get the readings that are on the graph in the FSM. The info is getting to the ECU thats for sure. I have to rule out the CHTS as an issue at this point. Or no? Edited May 26, 2016 by rickyellow zee Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 26, 2016 Author Share Posted May 26, 2016 Next up I want to try another AFM and see if that helps. Quote Link to comment Share on other sites More sharing options...
Equizyme Posted May 26, 2016 Share Posted May 26, 2016 what kind of mileage is poor? what's your drivetrain like? 4 speed, 5 speed? i may be wrong about this but it's my understanding that when you go WOT any and all adaptivity from the ecu goes out the window and it runs basically full fuel demand, obviously mitigated a bit by the fpr. i have an 81 zxt motor in my 77' and i get black smoke when i get on it. a little isn't necessarily a bad thing. i would be more worried if it was affecting driveability. the fact that you seem to be getting normal A/F ratio's under all condition aside from WOT would make me think everything's working just fine. 10-12:1 is where you will make the most power from my understanding. Quote Link to comment Share on other sites More sharing options...
rickyellow zee Posted May 26, 2016 Author Share Posted May 26, 2016 Thank you first off. Its a 5 speed..... Like I said Im new to the L series. It could be that everything is fine, Maybe, I dont really know. lol. My other turbo car does run leaner and no black smoke when I get on it but thats another car all together that has been fine tuned over years. In the future I plan on going megasquirt but thats after I reach the current ECU, injector and turbos limits. I would like to see what the current setup is capable of first when running properly. It just seems odd that when a sensor is unplugged it acts like nothing has happened. Ive read other posts regarding the CHTS and when it gets unplugged the idle usually goes to shit. Mine does not. Dunno man. Quote Link to comment Share on other sites More sharing options...
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