So I bought myself a 1991 non turbo 300zx last week and it is unhappy. It reads code 42 and had a hesitation from idle (witch is 1500rpm so some resin) to high in the revs and was stuttering when I was just cruising, I replaced the fuel temp sensor and that helped a lot, now only hesitates from idle to 2000rpm, I checked the ohms between the ecu and ground and that's fine. And I cleared the codes by going into mode 2 twice but it still reads code 42. Any help would be awesome
Check the connections were clean, also have a look at your knock sensor, and the MAF and clean all the connections and replace any part that's stuffed.
Sounds like a wiring issue between the ECU and the fuel temp sensor wire. Check for continuity, if it comes back ok, wiggle sections of the harness. You might have an intermittent connection in the loom. With your revs being too high at idle, might need to adjust your idle and/or tps. Find someone with data scan, or get a consult cable and the software yourself. Easier to do by data scan, otherwise check the tech section to do the adjustment without Datascan.
i will look at the knock sensor tomorrow, as for the air sensor MAF.. that is all good. checked that today. checked the air reg and ACC valve omhs today also and there good. i did notice that i pushed down on the passenger side throttle linkage and it moved about 1/2mm -1mm and the idle did drop to normal, but it just spring back up to 1500rpm. will check that out tomorrow as well.
tryed setting the idle via the little flat head screw and it does nothing....? and as for the tps i move it and the revs drop but then a second later it goes back up. i will look into buying the consult cable and checking sections of the fuel temp sensor harness because all is good when i put my omhs thing between the ecu and ground. thank you heaps
to set the idle you need to disconnect the idle control solenoid. also it needs to be done with a warm engine or else it will be affected by the cold start hardware. There is a toggle in most the free Z ECM software for setting base idle if you have access to it. As for your fuel Temp sensor make sure the earth connectors are properly fixed to the rear of the Plenum in fact make sure all your earths have a good connection.
Both earths are on and earthing fine. When I disconnect the thing with the flat head screw to adjust idle the revs don't drop like the book said it should. I can ajusting the idle and I have to 650rpm then plugged the wire back in and it stays at 650 it does not pick and and settle like the book said it should. So I just set it at 800rpm and today I was looking at the vacume line that goes to the fuel pressure reg and when I rev it from idle it stops sucking till about 2000rpm???? Also I have orrded another new fuel temp sensor just incase the first one was dodgy.
ok so I found a blown "eng cont" fuse the other day :\ don't know why I did not start off with checking fuses but oh well. so I replaced it also put a new timing belt and water pump on. the timing on the driver side cams where out by a fair bit so there all better now and the car runs much better. less of a flat spot. but a new problem has come up, when Im just driving along being a nice and only just touching the throttle pedal there car bunny hops?? in 4th doing 50km/h sitting just under 2000rpm ???? does it in every gear when my foot only just touching the peddle when I take it off its all good when I push the peddle harder its all good.... I reset the base idle with no luck. and im still waiting for the new fuel temp sensor to rule that out but any other info would be nice.
Whats your TPS reading? should be .44 - .46V, if this is out readjust TPS to the above figure, then disconnect the grey plug on the TPS for 20secs then reconnect plug. RPM should then fall, if not disconnect idle control solenoid, set idle on manual control screw to 700rpm, then reconnect idle control solenoid. If you find that you have no adjustment on idle manual control, then you need to take idle control unit off and clean it out. Its not unusual for this to get clogged up
tps is reading .45v but the hard idle switch is reading 0v now. I found out that along with my fuel temp sensor my o2 sensors are dead. replacing them next week hopefully then it will run and idle with no flat spot and I can start putting money into the gearbox and body work.
Every thing is good besides the code 42 now . Brand new sensor in today. Ecu mite be the problem ? Should I get a new one
