Hi there everybody, new here to the z forums. Just picked up my beautiful red 300zx with 110k original miles and couldn't be happier (especially after owning an mk3 supra). The car is a na, 5 speed with a digital gauge cluster and a working ****in Betty! I am used to buying used cars and am very familiar with how to go about making sure a 20 yr old car has everything it needs. However it has a bit of a running problem that I'd like a little advice on being new to the vg30. Note: I have replaced fuel filter, plugs, cap and rotor and have seafoamed it to clean the insides a good amount. Also cleaned the iac ( boy was that sludges up). So anyway it has a constant miss at idle, not constant like I have a dead cylinder just never smooths out completely. Everytime i cold start it, it will bog until it stalls 2-3x then it will be fine. Coming to a stop the idle will be at 800 for 15 sec until it picks up to 1300. It will do this over and iver again (fall and rise)I've checked for vac leaks and turned up dry, don't hear any hissing either. I get a code 23 and 31 (ac doesn't work) can anyone clarify what 23 actually points at? I checked tps and get NO voltage at any of the tabs no matter how I set it up ( I had the key turned to on). Is this even possible? I've never had no voltage like that before. It seems like the previous owner liked to "tinker" so I may be chasing a wire short ghost somewhere. Any help is appreciated thanks!

 

Code 23 is the TPS (at least for the 84-86 Z31's)... ECU: How to Read and Diagnose Z31 Codes: 84-86 ONLY - Nissan Forums: Nissan Forum

Have you ohm tested the tps & wiring?

 

generally the codes are useless. take all that idle crap off the plenum on the drivers side. all it does is cause problems. general advice after doing 3 z31 follows

Get your battery load tested. Be sure you have clean, tight corrosion free terminals on both ends of your battery cables. Be sure the ground (negative) cable goes to a bolt into the frame before going to the starter. grounding through the starter is not a reliable connection. Z's don't like low voltage. causes the electronics to act funny. it is possible to have enough amps to crank but not enough voltage to run the electronics. If you have one size fit all cheapo clamp on terminals they are a problem waiting to happen.

Clean the connectors for the maf or afm, ecu and tps. Deoxit by CAIG is probably the best connector cleaner on the market. spray with CorrosionX after cleaning and before putting together this will help prevent any further corrosion.

Replace outer tie rod ends, and ball joints. replace the bushings with poly (don't forget to lube them as directed unless you like squeaky things). New shocks. all those things will make you think you are driving a different car. doing them piece meal is a waste you won't see a great improvement until you do the complete job. Rear bushings nice too but more work and you won't notice as great an improvement. Rear shocks also because if the fronts are gone so are the rears. if car squats when you jump on the gas the rears are gone. If you have the electro adjustable shocks they are DEFINITELY GONE. test or replace the chts. set the tps per the manual. check the fuel pressure

 

i just put a vg30et into a d21 4x4. it was a pain in the but but i got it in there. now that i got it running it has some issues. it throws the code for speed sensor and nuterak safty switch. do either one of those make the motor run better. right now it runs good with the hood open and not when its closed. it sometimes runs good and then it doesnt. any help would be appriciated. thanks

 

when you shut the hood does it short out the battery? speed sensor neutral switch got no effect on running. since you didn't put it in a z31 hard to tell what your problem might be from your limited information post. the speed sensor will limit the speed of the engine if it is hooked up to the wrong input. I have got to guess that nuterak is a vain attempt to spell neutral

 

hey there thanks for the responses. been havin some nasty weather so just got a chance to get under thre hood today. checked the tps and wiring with ohms instead of volts.. still nothing from any point of contact combination. so most likely thats gone out, even tried opening the throttle slowly on all points just to see and still nothing. will probably order that today.

now heres something that worries me, there are 2 black wires coming from the harness where the ecu is stored and they arent connected to anything. one is a single wire with 1 flat female contact while the other is a 3 point female contact. any ideas? cant figure out where in the hell they go to.


and thank you rogerz for the info! will definitley look into that although the last owner said all the suspension is brand new (will inquire about what exactly hes talking about) also cleaned all the connectors you mentioned and still nothing. and i will be removing the iac, as long as its fine without it, thatll clean up the top of the engine a bit im sure. as far as electrical goes none of my gauges ever act funny, nore does anything dim while the lights are on. i will keep an eye on that though.

 

Replaced tps after auto zone lost the damn thing and left me waiting for two days had no effect at all. Checked timing and it's fine. Gonna do some problem hunting over the week and check back here. Also starting is becoming ever more difficult. Used to just require slight blip of the throttle and it would start fine. Now it takes about 1 1/2 minutes to cold start it. Warm starts are still immediate. Any advice is welcome thanks!

 

tps is just a switch no magic there. it leans out the mix when in idle to save fuel. what is your fuel pressure? what is your vacuum? vacuum leaks are the bane of an FI engine. are all your hoses that connect to anything vacuum in good shape. inspect the large rubber tubes connecting your intake air. leaks after the maf cause unmetered air to throw off the mixture. ecu only knows what you tell it. gigo garbage in garbage out.
I wouldn't worry too much about the extra wires if it is running. if your only problem is hard starts that isn't the problem. you will find a lot of extra wires on a z31 depending on model which just end in the air. if all the suspension work involved shocks and springs then you still need the other. people tend to think that new shocks and after market springs solve all their problems. my opinion the stock springs are fine if you do everything else. did you check the chts? it will do funny things if not right. again gigo

did you download the fsm from xenon. it is good after you use it a bit it makes more sense. Japanese logic different from ours. I had the same trouble using german stuff. they solve the same problem a different way works just different.

 

Well tested the fuel pressure after waiting for auto zones kit for 2 days. Think I found the problem, pressure reads 29 at idle. Removed the vac line from the pressure regulator and the gauge jumped 10 psi like it should if the regulator was working fine, correct? So this points the fuel pump if I'm not mistaken? Also just FYI my vacuum test came back ok, read 19 at idle. Thanks for the help rogerz. Downloaded that fsm too hope that'll keep me off the posting side of the forums from now on lol.

 

Just read the fsm and it says at idle it should read 30psi so it seems I have not found my problem I can't find the normal specs for vacuum at idle does anyone know what it should be?

 

i have a 1990 nissan 300zx turbo and would like to know if i could do something simple with it?