1986 n/a 5spd, used to hesitate above 4k, now rough all around
Thread Starter
Registered User
Joined: Jan 2015
Posts: 51
From: Bellevue, WA
1986 n/a 5spd, used to hesitate above 4k, now rough all around
I've searched, and the first few pages don't have any matching problems, so here it goes:
I've owned it for a few months now, ran perfectly. Put about 4/5K miles on it. About a few days ago, I noticed when I am in the 4000-4200 RPM range, it really struggles, more or less than that and it's just fine.
Today, it's gotten much worse. I almost couldn't make it home.
Seems like a fuel delivery issue? What's some really easy stuff I can check/replace?
I've owned it for a few months now, ran perfectly. Put about 4/5K miles on it. About a few days ago, I noticed when I am in the 4000-4200 RPM range, it really struggles, more or less than that and it's just fine.
Today, it's gotten much worse. I almost couldn't make it home.
Seems like a fuel delivery issue? What's some really easy stuff I can check/replace?
Grumpy & Helpful
Joined: Sep 2006
Posts: 1,415
From: Mill Creek WA
doubt it is a fuel delivery issue in that it runs well below and above that range. A faulty fpr would fail above a certain rpm and then just continue to degrade. I'd look at something electrical. New dizzy cap and rotor might be all you need. my 85T had a miss when floored that disappeared once I did that. after that CHTS or O2 sensor might be a guess. Come to our (Z car club of Washington) next meet at the Red Hook Brewery in Woodinville May 12 Starts at 7pm but usually people come earlier. Meet the guys and pick some brains. ZCCW.org website. You don't need to be a member to meet up with us. We also have a drive to North Cascades on May 30.
Thread Starter
Registered User
Joined: Jan 2015
Posts: 51
From: Bellevue, WA
doubt it is a fuel delivery issue in that it runs well below and above that range. A faulty fpr would fail above a certain rpm and then just continue to degrade. I'd look at something electrical. New dizzy cap and rotor might be all you need. my 85T had a miss when floored that disappeared once I did that. after that CHTS or O2 sensor might be a guess. Come to our (Z car club of Washington) next meet at the Red Hook Brewery in Woodinville May 12 Starts at 7pm but usually people come earlier. Meet the guys and pick some brains. ZCCW.org website. You don't need to be a member to meet up with us. We also have a drive to North Cascades on May 30.
Seems like something is degrading. I went to the store, and when I got back in the car, it all of a sudden started hesitating and choking across the band
Also, thank you for the invite. I'll have to come by!
Grumpy & Helpful
Joined: Sep 2006
Posts: 1,415
From: Mill Creek WA
jury rig a fuel pressure gage that you can see while driving.
this would work or you could go to OReily and buy an oil pressure gage and some fittings. that 1/8 inch plastic tube that often comes with it is stiff enough to thread under the hood and then close the hood and have the gage where you can see it while driving. might be your fuel pressure regulator is heading south. Fuel filter? need to put a gage on there and either confirm or eliminate fuel system as the problem.
if you were north of seattle we could meet up and do some testing but going to federal way is like the ends of the earth due to I-5 traffic.
this would work or you could go to OReily and buy an oil pressure gage and some fittings. that 1/8 inch plastic tube that often comes with it is stiff enough to thread under the hood and then close the hood and have the gage where you can see it while driving. might be your fuel pressure regulator is heading south. Fuel filter? need to put a gage on there and either confirm or eliminate fuel system as the problem.
if you were north of seattle we could meet up and do some testing but going to federal way is like the ends of the earth due to I-5 traffic.
Thread Starter
Registered User
Joined: Jan 2015
Posts: 51
From: Bellevue, WA
jury rig a fuel pressure gage that you can see while driving.
Amazon.com: Actron CP7838 Professional Fuel Pressure Tester: Automotive
this would work or you could go to OReily and buy an oil pressure gage and some fittings. that 1/8 inch plastic tube that often comes with it is stiff enough to thread under the hood and then close the hood and have the gage where you can see it while driving. might be your fuel pressure regulator is heading south. Fuel filter? need to put a gage on there and either confirm or eliminate fuel system as the problem.
if you were north of seattle we could meet up and do some testing but going to federal way is like the ends of the earth due to I-5 traffic.
Amazon.com: Actron CP7838 Professional Fuel Pressure Tester: Automotive
this would work or you could go to OReily and buy an oil pressure gage and some fittings. that 1/8 inch plastic tube that often comes with it is stiff enough to thread under the hood and then close the hood and have the gage where you can see it while driving. might be your fuel pressure regulator is heading south. Fuel filter? need to put a gage on there and either confirm or eliminate fuel system as the problem.
if you were north of seattle we could meet up and do some testing but going to federal way is like the ends of the earth due to I-5 traffic.
Grumpy & Helpful
Joined: Sep 2006
Posts: 1,415
From: Mill Creek WA
yes i have a lot been thru 3 z31 and 4 s130. if your car will make woodinville come to the meeting. i'll bring some stuff. email is krs@whidbey.com. probably easier than trading thru the forum pages.
Thread Starter
Registered User
Joined: Jan 2015
Posts: 51
From: Bellevue, WA
Replaced the fuel pressure regulator, and now it wont idle. She starts up, then almost immediately dies. Next few tries she immediately dies. Give it a few minutes and it repeats this behavior
Registered User
Joined: Aug 2013
Posts: 1,103
I would check the 2 solenoids on your air regulator, one for idle-up, the other for fast idle control. Before they die they can act intermittently - just to make you crazy. 
Easy test with your tester. Take them out, power them on and off in your hand. You can feel the click inside if they are working right.
Easy test with your tester. Take them out, power them on and off in your hand. You can feel the click inside if they are working right.
Last edited by zxguy1986; May 15, 2015 at 02:20 PM.
Thread Starter
Registered User
Joined: Jan 2015
Posts: 51
From: Bellevue, WA
I would check the 2 solenoids on your air regulator, one for idle-up, the other for fast idle control. Before they die they can act intermittently - just to make you crazy. Easy test with your tester. Take them out, power them on and off in your hand. You can feel the click inside if they are working right.
Easy test with your tester. Take them out, power them on and off in your hand. You can feel the click inside if they are working right.I've now replaced all hoses near the FPR and its still a no-go
What could changing the FPR possibly have broken that I already haven't replaced???
Registered User
Joined: Aug 2013
Posts: 1,103
MAF a good place to check for dust, dirt and grime. Guys have blown it clean, carefully using cleaner - or just compressed air - but you're not supposed to touch anything in there while you clean it. You can check the archives here for MAF. I have replaced only one in my time, not a cheap deal if I remember..$400+? But ya gotta do what ya gotta do. 
Last edited by zxguy1986; May 16, 2015 at 07:27 AM.
Thread Starter
Registered User
Joined: Jan 2015
Posts: 51
From: Bellevue, WA
MAF a good place to check for dust, dirt and grime. Guys have blown it clean, carefully using cleaner - or just compressed air - but you're not supposed to touch anything in there while you clean it. You can check the archives here for MAF. I have replaced only one in my time, not a cheap deal if I remember..$400+? But ya gotta do what ya gotta do.
I'm starting to think more that it's not the maf. When it manages to start and stay started for a few seconds, giving it any gas will also kill it. It HAS to be something vacuum related, but I can't freaking figure out what. I've replaced so many vacuum lines and its still no go
Registered User
Joined: Aug 2013
Posts: 1,103
Check your vacuum line replacement work against Thumper's page. Lots of good pointers there. You may have missed or skipped something. Inside diameter of your lines is important because the vacuum system is not all that strong - and the diameter of the line can affect the vacuum power getting to those points where it is needed. And without a good OEM vacuum system, your engine is a loser. It's just the way Nissan designed it. Early 80s. Best they could do.
Vacuum Lines
At 29 years and counting, that Z should have had every OEM rubber vacuum line replaced by now. An orig OEM rubber line still working right would deserve an award!
Vacuum Lines
At 29 years and counting, that Z should have had every OEM rubber vacuum line replaced by now. An orig OEM rubber line still working right would deserve an award!
Last edited by zxguy1986; May 16, 2015 at 06:41 PM.
Thread Starter
Registered User
Joined: Jan 2015
Posts: 51
From: Bellevue, WA
Check your vacuum line replacement work against Thumper's page. Lots of good pointers there. You may have missed or skipped something. Inside diameter of your lines is important because the vacuum system is not all that strong - and the diameter of the line can affect the vacuum power getting to those points where it is needed. And without a good OEM vacuum system, your engine is a loser. It's just the way Nissan designed it. Early 80s. Best they could do.
Vacuum Lines
At 29 years and counting, that Z should have had every OEM rubber vacuum line replaced by now. An orig OEM rubber line still working right would deserve an award!
Vacuum Lines
At 29 years and counting, that Z should have had every OEM rubber vacuum line replaced by now. An orig OEM rubber line still working right would deserve an award!
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