jjk_52

Hello there! I just bought my 84 300zx and its been a long time dream. However after having the car a few days its developed a major hesitation issue. It did it all the time at first so I changed the fuel filter and regulator and it is better but after warming up it still does it. The car had sat for a year previous to me buying it however. The car is n/a automatic. also the digital dash fuel gauge doesn't work. I noticed that right around the time the chick voice tells me I'm "low on fuel" is when it starts acting up. it just sound like its not firing on all six. I noticed when I was driving if I just stomped the throttle it would kind of hesitate but power through it than almost be fine again. I've checked al the basic things I could think of but I don't know where to go from here. Please help!! this was supposed to be my daily driver but now I'm wheel-less

rogerz

sounds like a problem with low fuel in the tank. If it doesn't do it when the tank is full just watch your mileage (figure around 20 mpg). 19 gallon tank so when you hit 200 miles fill it up again. doesn't fix your problem but you can drive around. you need to check your fuel pressure and vacuum to get a reasonable answer. since you don't seem to be shy about throwing parts at a problem with no data replace the chts and the o2 sensor. download the fsm from xenon you would be surprised at the information available therein.

zdadgeezer

sending unit part #.
Analog part number: 25060-17P65
Digital part number: 25060-17P75

As rogerz stated download the manual. Then check and if they show any sign of being original replace all the vacuum lines.

Z Fest in Aug. Check Ontario Z car site. www.ontariozcar.com

zxguy1986

When you buy any used car, you have to figure that it has not been maintained as often and as well as you would have maintained it - so there is always some catching up to do. That's where you are with your 'new' Z. No reason it can't be the daily driver you want when you have finally caught up.

Get the Factory Service Manual (fsm) from XenonZ31 Reference. It has great inspection and maintenance sections for almost everything. Find the diagnostic section and run the ECU (computer) engine diagnostic, making a list of the trouble codes that tells you. Could be informative and will give you a general idea of the car's basic health at this point. Feel free to ask your questions here.

On the bright side, your car is 30 years old and runs as well as it does. I think there's something of a miracle in that. It is loaded with 30-yr old original parts, most of which are still working perfectly, a few of which are tired or just plain dead and need to be replaced. Finding and replacing them goes with the territory and is half the Z fun for most of us. Your Z has been missing the TLC you have started to give it. Keep up the good work!

PredatorZ

Make sure all your fuel injection connectors, Map connector and TPS connectors are all clean, free of corrosion and have a good tight fit. Bad or poor contacts and a poor ground can cause all kinds of issues. You can add an extra ground wire from your intake to your neg Battery, and another to the firewall and engine. Has your engine bay been power washed, or has it been wet or raining lately ?

jjk_52

I'm a third year apprentice I'm not just throwing parts at it without any data. The fuel tank is full of great Canadian premium fuel so that's not the issue (also I have the FSM I'm not totally retarded)
I replaced the fuel parts as part of a recommendation from a Nissan tech since 1979. Today I'm going to try replacing the plugs cap and rotor. The past few days its ran perfectly in the morning but as the day warms up it starts giving issues. When the problem starts if I just put it in neutral and shut it off, when I restart it, it will run fine for another five minutes then the issue starts again. I've tried checking all the connections but ill try that again also. Thanks for the support guys its a lot of help!

rogerz

fairly classic symptoms of a bad chts. it would make you seem less like a tyro if you would include some information in your post. LIKE fuel pressure, vacuum and other tests you have done. include "all the basic things I could think of" A third year apprentice needed an old timer to tell him to change the fuel filter? Doesn't say much for what you are learning. if you are calling the fpr a regulator it would have been a lot simpler and cheaper to put a gage on the fuel ring and find out whether it was bad or not. You are wasting money on that great canadian premium unless you are running about 12 psi boost on a turbo. that is another piece of info you neglected to include ie n/a turbo. They are similar but different animals when it comes to what might be wrong.

jjk_52

I went to the guy so that I wouldn't have to just guess and waste money. The premium fuel was because the car had sat awhile. My apologies for not mentioning it was N/A but if your not going to help and just rag on a young kid trying to fix a car on a shoe-string budget then go away! I was asking for help not to have some jerk rag on me like that.

jjk_52

To everyone else who had been helpful; I've noticed that whenever the chick comes on to tell my fuel is low almost instantly is when the issue starts. Could the fact that the fuel gauge doesn't work effect the fuel delivery? I was thinking that maybe the ecu starts freaking out due to the gauge, so I was going to replace the gauges but I really don't want to waste money replacing anything else (my girlfriend wont lemme spend anymore till I know exactly the issue haha) I did however change the plugs cap and rotor and the plug wires just to rule out anything simple. I just cant believe that its a coincidence that the very second the issue starts is when the digital system says low fuel..... It does it every single time. its weird....

jjk_52

I was checking all my connectors again as advised and I found the one on my air regulator to be cracked up and corroded decently bad. could the air regulator possibly have part to do with the issue? And im pretty sure this is going to sound dumb but what is a CHTS????

--Also, I ws going through all the other posts similar to my issue and found one saying unplug the tps and if it makes no difference than that's the issue. well I unplugged it and it made zero changes. but its a 120$ part so im nervous to go buy it.....

jjk_52

Tracked down a used tps and it made no difference. I think Im just going to scrap the car. I've put the purchase price back into it without any luck. Unless someone can tell me what the hech a CHTS is because "rogerz " suggested that but no one nor google knows what the hell it is. At this point I've pretty well gave up...

PredatorZ

easy peasy, as far as exact location, I will check and get back to you.

jjk_52

Thank you!!! I dunno what else to do, everything else seems perfect. Other than a ecu swap I'm running outta options. And I definitely can't afford another ecu

rogerz

do the chts. cheap and easy. search on line for a post on how to do it without a lot of extra work. Might be on MSA. you say it has nothing to do with fuel level and in the next breath you say everytime you get low fuel you have problems. which is it? I still say you should drive the thing and refill after 200 miles. See if you still have the stumbles. Do the Chts they can do weird things. whatever guy you went to I wouldn't do it again. replacing a part with no data (like fuel pressure) is the mark of the PARTS REPLACING MECHANIC. he can't diagnose an issue but he sure can charge you for parts
you say I am insensitive but your posts aren't exactly paragons of accuracy nor knowledge. bragging on being a third year apprentice, in what you don't say, whilst making silly and contradicting statements doesn't lend much credence to your statements.

jjk_52

I said my fuel gauge doesn't work so when the chick chimes in saying low fuel (because of the gauge not working) is when the issue starts. Pay attention to what has been wrote I never once contradicted myself. Nor was I bragging I was just pointing out the fact that I'm not a complete and utter retard.

rogerz

Your gage might not work but the sender is because that is what is telling bitchin betty low fuel. so whether your gage works or not is immaterial. WHEN YOU HAVE LOW FUEL YOU GET AN ISSUE WITH FUEL DELIVERY. Wake up and smell the coffee boy! you are hearing from someone with a lot more experience on Z31's. Since you didn't bother to put a pressure gage on your fuel ring you have no idea what is going on. next time she gripes pull over and see how much fuel you need to fill the tank. Holds 19 gallon in case you didn't get that the first time I put it in. hope you can work out what 19 US gallons is in Liters which I think you guys use now.

jjk_52

okay I understand what you mean. However I've kept the tank full the entire time and it does it no matter the fuel level. I've gone through about two tanks of fuel now but I've been making sure its always full. Betty Bitches at me that the fuel level is low even when I know for a fact the tank is full to the brim that's why I figured the gauge made her yell. I'll see if I can rent a pressure gauge or something from a local shop. If it was a fuel pressure issue would it work fine for five minutes before the issue starts? I just sort of figured that if it was a low pressure problem it would happen nearly right away not after awhile, and in the mornings almost not at all.....

rogerz

then there is something wrong with the sender. you should see full tank. then goes down to quarter tank and the little needle begins to move (unless you got digi then a five should show up). the last switch is what triggers betty. do you get a yellow light? possible some wires frayed or grounded somehow. easy to pull the sender. probably looks like an aluminum tube. six bolts under the carpet. there is a wire loop that you slide a bar under then gently lift it out. procedure in the fsm (you did get right?) You really need to get a pressure gage but some fiddling around to do that. On my 86 I put a tee in the line to a sender. Harbor freight oil pressure gage they used to be $22. then just need to run some electricity out the hood and in the widow. tape the gage to the dash for temporary and see if you get a pressure drop when she starts to stutter. does the fpr have a vac hose on it. it varies fuel pressure by vacuum. Don't give up on it. It runs you just have a driveability issue. they are good cars when you get em right. unless you got a mouse nest in the air intake I'd say you have fuel delivery issue. might be bad pump but you need that gage to diagnose. to the best of my knowledge there is no reason for the fuel warning to affect running. On my 85 she would be yakking for miles but never a stutter. both 86 the same. Other possibility but getting out there is something loose in the dizzy but I think you would have noticed when changed cap and rotor. Once again be sure you have an excellent ground and good terminals on your battery cables. I still get stuff from my wife cause I took her for a ride in the (new to me 85T) even tho I knew cables were suspect we stalled out. cost me a set of diamond earrings. See I can be nice when you make the effort to say I did this I just didn't sit on my hands. Replace that chts. all z31 I have had or knew about liked getting a new one.

you could just to be sure pull the ecu and open the cover look for burnt resistors, diodes or capacitors. I think your problem is not too complicated just need to keep at it. i strongly lean to the fuel delivery as a problem. Vacuum problems are the bane of an FI engine while at it why not stick on a vacuum gage. cheap and you can run hose out and tape the gage by the window. At the very least check the vacuum while idling. 84 probably your vac hoses are shot.

jjk_52

It's the digital dash and the fuel light is always on. I have a replacement gauge set on the way should be here next week. Once that's working I'll definitely look into the sender. I agree that it's some weird fuel delivery issue. I won't give up yet!

rogerz

now you're talking. here is some general advice that I give everyone. better ride and might save grief down the line:
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. Get new boots for power steering. 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. You need to get the car realigned after messing with the front. Have your tires in good shape and rebalance. 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.

If you are doing a turbo car shocks (electro adjust I think may be only on the turbos) then you need the adapter plates to fit modern shocks to the car. Easiest way is find an n/a at the junkyard and take the mounting plates. They may be available thru NAPA (listed) but I had the n/a plates. you can get a sender from Courtesy Nissan. $140 I think. just did my 86 because I'm trying to get her 90% complete and finally not getting the 5 lit up on fuel section was something I could no longer tolerate.

PredatorZ

it is tucked away in a somewhat hard to get location, you have to remove the Timing belt cover to get to it, and unless you bend the sheet metal between it and a cam sprocket, you will need to remove the timing belt to change it. Here is a YouTube video a guy shows the shortcut way to do it.

ch33z3x

There may be crud sitting in the bottom of the tank because it sat for awhile. Make sure your tank is clean when you change your sending unit. I had an MX-6 with this problem, when it was nearing empty and starting to act up, I pulled my new fuel filter - and it was clogged. There is NO pickup screen on these pumps, either. Cleaning those electrical connectors is very important - I noticed results instantly when I cleaned mine, the idle improved dramatically. Cleaning the MAF itself may help as well. If you do the CHTS, the connector is generally corroded. I found an injector plug from a sentra that fits (paid 5 bucks, 9 inches of harness attached. Pick n pull ftw!), with minor modification. It's a standard Nissan connector, and an easy fix while you're in there.

rogerz

here is the easy way if you do a search
z31.com | Repairs | Changing the CHTS the Easy Way

some tips from experience: only snug it down it doesn't need to be tight just good contact with the head metal. Too tight you can damage the sensor. get a new or better connector. Volvos have really high quality ones. Find the volvo section of the junkyard and start cutting them off unfortunately you only get four per car. You can also use them to replace your present Nissan lo quality connectors Cut off the oval connector that sits atop the engine probably fried anyway. use solder gun and heatshrink to make a good least resistance install. injector connector and chts connector are the same.

other thoughts - if you do not know when the timing belt was changed you had better do so. if it goes you pretty much ruin the engine.