300zx Update (More MAF Issues) 300zx Z31

[@derekjansz2950]

I've had a very similar issue before on the 85 I used to have. In my case I think the issue was a combination of a bad MAF and a bad ground to the crank positioning sensor. So what I would try, if the connector you ordered doesn't fix the issue, is to replace the MAF wiring harness since it seems your issue is in the MAF circuit. The wiring in these cars really seems to be their Achilles heel. Good luck and thanks for the videos!

[@TheZGarage]

Thanks! I'm going to be getting the new connector installed because I found that is the bad point in the circuit

[@franklynpertuz7669]

Yes I have the same problem I just got my 85 running yeah Lotto has a lot of wire issues Battleground check the cylinder head sensor

[@franklynpertuz7669]

Anyways good luck with it

[@atomikrobot300099]

If you’re going into a STEM field, consider taking a large I/O a/d count microcontroller and wire it into all the sensors (to log all the data). I did this during my EE undergrad while diagnosing my z31 88 Turbo. I had a closed loop issue which ended up being an O2 sensor issue (the O2 sensor behaved perfectly under test, but under WOT it would misbehave - logging all the data made it stand out as the culprit). Maybe try running a temporary harness back to the ECU to rule out the MAF wiring?

[@jy1235689]

Crazy this car made me excited too about my EE classes since it was mostly analog electronics.

[@gekkoman4853]

What

[@stuckonline3985]

i may be late to the party but i had this problem about 8 years ago which was a result of water leaking through windscreen into ecu destroying the fuel pump circuit, the fuel pump cuts off about 10 seconds after starting the car unless you put your foot on the gas raising the revs, i have a second ecu that works but it operates on a different o2 sensor so i just added a fuel pump relay that turns on when the ignition is on, car no longer cuts out. if it was an air flow sensor issue it wont happen with sensor unplugged but you also wont be able to go over 3thou revs with no air flow sensor

[@worldpeace5849]

You can send it to rockauto and they will rebuild it.. I had the same issue... after rebuilding the MAF same issues.. it turned out both grounds from the MAF connector need to be grounded to the body. I spliced wired leading from c & d and grounded them to the body - runs fine now. I literally tested all leads to ECU..

[@Dookieandsons]

I don't mean to be a pain in your ass I just wanted to let you know I really respect your videos I've had these cars for 20 years I know I told you that a million times I've got a picture of me in front of my first one in July of 99 it was my slick top 84 Datsun LOL but I just wanted to tell you that I put your videos playing back-to-back and listen just to learn anything I don't already know and get ideas and advice I listen to you even when I can't watch your videos I just listen through my Bluetooth while I'm walking around at work I've recently started a little KZbin video and I'm going to start making them better but mine's just more less to show off my car and I really don't work like you do on video but I do show off a lot of things and show my new parts but you've motivated me to do the KZbin channel you know I'm not trying to compete against you or anything like that but I just love seeing videos of the Seas when I come across them I had to add mine to it too anyways save as many of them cars as you can busy car anyway I want the z32 I have a 74 240Z it's going to be a strictly v8 car though I wish I still had my 87 but it got stolen when I was in a wheelchair but anyways I'll still have my 86 that I've tried to get you to look at there's multiple videos on my KZbin of it I'm done about everything I want to do to mine other than paid it turbo it and coilover and I'll be finished pretty much

[@atomikrobot300099]

Compare what values you get at the MAF and at the ECU plug to rule out the wiring.

[@TheZGarage]

That's a great idea! I'll definitely try it out! Thanks

[@WARRIOR4CHRIST70]

I love your channel, can you help me with a question I just purchased a 1984 300ZX turbo. And I noticed they have the same cold air intake filter like you do. But he left the old equipment in the trunk. Why is everyone removing the old filter and putting in this cone looking one like you have?

[@TheZGarage]

For me it was mostly because it creates induction noise. The factory box is very good a keeping the noise down and with a cone filter you can hear it a lot better when you jab the throttle. That being said there's really no real advantages in any other regard

[@gekkoman4853]

Do these cars have IAC valve? If you have to feather the accelerator air may not be bypassing the butterfly valve… could try cleaning

[@adamshook6039]

I'm having the same exact issue with my Z, I went ahead and changed out injectors, FPR, spark plugs and wires and will still have to feather it to hold the idle

[@TheZGarage]

You may just need to adjust the idle control valve on the side of the intake plenum. I would also check your Tps to make sure it's calibrated properly

[@adamshook6039]

@@TheZGarage awesome Thankyou i will do that! I unplugged that maf and ran perfectly up until 2000 rpm, also running very rich

[@adamshook6039]

I'm also new to these Z engines so learning as I go hahaha

[@bryandm7]

Where could I find a replacement MAF for my Z31? Could I use a Z32 MAF?. My z31 only starts/runs under 2000rpm with the MAF unplugged, won’t run at all with it installed. Any advice would help thanks !

[@TheZGarage]

You can get them from parts cars, used of course. A lot of people have them sitting around. Or you can send yours in to get rebuilt on rockauto. (they also have a new one but it's 550 dollars)

[@guayoz28]

I am curious to know what the fox to this problem was. Im having the exact same issue. I sometimes start the car and runs fine, after few mins it stalls, sometimes it will run very rough since starting it. i hit the gas and it revs up for a second and comes right down amd stalls or almost stalls. Please help!!

[@mrslapside]

Have you fixed it? I got same issue

[@jeffwolfe4058]

My 85 NA starts but only idles and with and gas pedal it dies immediately. Been trying to figure it out. Would you look to the MAF

[@TheZGarage]

It's always good practice to clean the maf just to make sure it's reading as accurate as possible, but if it runs well with the throttle pressed slightly, you may just need to adjust your idle and possibly the throttle position sensor.

[@stuckonline3985]

read my post above, this is a fuel pressure issue. and unfortunately is most likely your ecu, open it and see if anything looks burnt out, if so just rewire a fuel pump relay to the ignition to keep the pump going when the key is on as the ecu will be shutting the fuel supply off again

[@jefff1016]

Did you find what the MAF issue was? Also I have an 86NA which actually runs ok - feels like a bit of stumbling sometimes on idle. I unplugged the MAF and it was definitely worse, wouldn't run at all, just start and die.

[@TheZGarage]

If it runs bad with the maf unplugged then you have something else going on. I would check timing (mechanical and electronic), CHTS, and fuel pressure.

[@jefff1016]

@@TheZGarage it's a strange one though, like I said it runs pretty good with the MAF plugged in. Believe timing and fuel pressure are fine. CHTS is a big question mark though. Maybe the MAF is slightly off and I've adjusted the idle too low to compensate?

[@rawhide1231]

Hello again guy, was just watching your MAF videos again thinking maybe that has something to do with my current issue in my 85. I have tried all the forums with absolutely no luck so the hunt to find a solution for my mid range power loss continues and it's driving me mad. It's a long story but have you ever had a power loss around 2500 rpm that drops back to 1500 rpm and pulsates back to 2500? I looked through your videos and didn't see anything similar so I thought I would ask you directly. Thanks for your time. LB

[@TheZGarage]

Do you have an automatic transmission by chance?

[@chrisrizo5264]

Where can you locate the check engine light connecter on the ZX?

[@TheZGarage]

I'm not sure which connector you're referring to. There is a 'sensor' light in the dash but that doesn't really do much and then there's a diagnostics mode in the ecu

[@greasemmonkey]

Have you fixed it yet? I’m having the same problem when I unplug the maf it runs only to about 2000 rpm

[@TheZGarage]

When you unplug the maf that is what it's supposed to do. My problem was actually my fuel pressure. The maf was reading correct but the fuel pressure was too low so it was running lean

[@greasemmonkey]

Ok I will check it when I get home

[@mikecorleone6797]

My z has the same issue.. I’m trying to figure it out.. the idle smooths out when I disconnect the vacuum on the fuel regulator but has new regulator and new pump.. 🤔

[@TheZGarage]

Unhooking the fuel regulator will make it run richer and mask any problems. Have you checked the ecu for codes?

[@mikecorleone6797]

@@TheZGarage no codes so far. It just flashes all good

[@mikecorleone6797]

I limped it over to the muffler shop with the maf disconnected because that’s the only way i can get it to idle smoothly.. second time my cat was stolen this month...

[@TheZGarage]

When was the last time you replaced the CHTS? If it's bad it can idle and run bad without throwing codes

[@mikecorleone6797]

@@TheZGarage it has a brand new chts sensor.. i just replaced it a few days ago thinking that was the issue. Replaced the water pump and timing belt n tensioner while i was in there

[@englishbannana1232]

So my 85 Z31 is having a similar issue but i checked the maf and it looked fine. What my car does is it runs and cranks up just fine but when it gets to a certain RPM it bogs down and doesn't wanna go any higher in rpms. Any idea of what it could be?

[@TheZGarage]

Does it rev freely in neutral? Have you checked the ecu for codes?

[@englishbannana1232]

@@TheZGarage no its an auto so when its in park or neutral it bogs down. I dont know how to check any ecu codes

[@TheZGarage]

What rpm does it start to bog at? If it's fine under 2.5k but over it starts to bog, it's definitely the maf

[@englishbannana1232]

@@TheZGarage my rpm gauge doesn't work but it sounds like its around 3 when it bogs down. But again im just assuming. It might be 2 im not entirely sure

[@TheZGarage]

It sounds like it's the maf. Unplug the maf and see if it changes at all. If it doesn't that's the problem

[@legendkiler619]

Did you ever fix this bro? I have a similar issue with a rough idle.

[@TheZGarage]

In my case it actually turned out to be low fuel pressure from a bad pump.

[@legendkiler619]

The Z Garage Ah well shit. I have a high idle around ~1400 rpm and I’ve tried everything but can’t seem to find the issue. I’ve replaced the intake coupler which had a little hole, all vacuum lines, did smoke test and deleted EGR bc it was leaking I believe, checked TPS, but nothing has changed. Any idea what else I should look at?

[@TheZGarage]

@@legendkiler619 1400 is pretty high. Adjust the idle down a bit (there's a small screw next to the throttle that it rests on, or the actual cable itself has adjustment nuts) and get it closer to 800-900, possibly higher since you removed the idle air control. Then readjust the tps. If that's still not making it better, make sure to check the ecu for codes.

[@legendkiler619]

The Z Garage I actually got the block off kit, and deleted the IACV but I couldn’t get the idle screw on the throttle body to budge so I put it back. I soaked that little screw in pb blaster and I’m going to try again tm. When I unplugged the IACV however it did go down to ~900 but it did kinda like “sputter”

[@TheZGarage]

Did you adjust the tps afterwards?

[@jy1235689]

That looks exactly like my slicktop

[@jy1235689]

White with red interior

[@luisantonio5288]

Mine wont even start without maf

[@brandonlyons1119]

I am having this exact issue on my Z31. Watching this video definitely helps with troubleshooting and diagnostics. Just super close to being able to drive my car again. Once i get the MAF figure out, I'll be able to take it back out on the road. Other than that, what was the ultimate fix you had to do to get your car running again?

[@TheZGarage]

I replaced my maf connector as I could wiggle mine and hear it change how it ran, and I also found I had low fuel pressure. Those two seemed to fix everything

[@brandonlyons1119]

@@TheZGarage okay cool. I bought a connector on eBay. For checking fuel pressure what are the normal numbers for the pressure and how did you check it?

[@TheZGarage]

I don't remember the exact numbers. I would look in the fsm on XenonZcar.com to see what it lists, but it's around 40psi. And you just tap into the line after the fuel filter. There's a rubber line that goes to the fuel rail. Just undo one side, use a spare piece and put the gauge right in line. That will be the exact pressure your fuel rail sees

[@brandonlyons1119]

@@TheZGarage sounds good. Thank you so much for the quick responses! I have subscribed to your channel!

[@coltonbarney7901]

How do I tell what maf I need

[@TheZGarage]

There are only 2. California, and everything else. Just match the color of the label on the maf. It's either blue or yellow

[@coltonbarney7901]

@@TheZGarage oh ok thank you so much

[@celsse66]

Nissan Service Manual 300ZX PDF Format, for free.

[@emanuelorozco1439]

I’ve unplugged my MAF and my car still won’t start

[@TheZGarage]

Then the maf is not your issue. You should look into fuel pressure, and the crank angle sensor. Check the ecu for Cas codes and put a timing light on it if you have access to one

[@emanuelorozco1439]

@@TheZGarage so I have done the fuel pump and filter. It has a new distributor which has the cas. My ecu has only given me a MAF code. I think my injectors might be clogged but I’m not sure. Thanks for the reply👍

[@TheZGarage]

I think you're on the right track. Have you verified that the spark plugs are actually sparking?

[@emanuelorozco1439]

@@TheZGarage I have not yet, but they are pretty black. I’m going to replace them.

[@ibm_businessman6033]

First