Stumble troubleshooting advice - Page 2 - Infamous Nissan

KivPanther · 02-20-2021, 05:13 AM

With the loose gas cap on the way home I noticed a few things. The stumble didn't go away, but it definitely seemed less intense. It also didn't start doing it until the engine had fully warmed up to operating temperature and only gradually came on once it did. Seems like I might consider replacing the gas cap and cleaning out the filler neck at the very least while hunting for the rest of it.

LugNut1990 · 02-20-2021, 09:18 PM

Interesting! If not a venting problem, next _guess_ is the fuel pump or sock. Before that (PITA job) I'd check out the wiring, grounds, etc. Be careful!

KivPanther · 02-21-2021, 08:02 PM

Shall do. I'm also going to run another can of seafoam in the crankcase since I noticed that the rockers and inside of the covers were covered in crud when I replaced the valve cover gaskets. Gotta love farm trucks driven by 90-something year olds!

KivPanther · 02-22-2021, 07:13 PM

I did a quick test on the gas cap valves per the FSM and found out that while the intake is working, the relief is not. So new gas cap anyway.

kenmack · 02-23-2021, 08:48 PM

You might consult the factory service manual (FSM) in the EF&EC section which has some good flow charts for servicing. You should start on page EF&EC-45 which will direct you to the flow chart specific to your issue.

KivPanther · 02-23-2021, 10:08 PM

I have practically memorized that section of the service manual. I'm still at a loss, hence my request for out-of-box thoughts.

Deerhurst · 02-24-2021, 01:00 AM

I got 2lbs of tannerite when you are fully fustrated!

Got a quick recap of what has been done to job our memories?

KivPanther · 02-24-2021, 07:07 PM

Sure thing. To date:

New distributor
New NGK Iridium plugs
New NGK plug wires
All new injectors and seals
Replaced a bunch of vacuum hose and can't find a leak with my current test methods (smoke)
New fuel pressure regulator
New fuel filter
Throttle body cleaned
MAF cleaned
Throttle Position Sensor tested working
Throttle wires adjusted correctly
Timing double-checked and steady at 15 BTDC
New gas cap
New air filter

To re-iterate, the stumble does not happen at idle or under full throttle acceleration. It only seems to do it when my foot is barely to lightly on the gas and only between about 2500-3200 RPM.

Deerhurst · 02-24-2021, 08:58 PM

Does the TPS have a dead spot? Easiest to see with an analog meter.

KivPanther · 02-25-2021, 04:30 AM

It seemed steady with my digital meter but I'll double-check. I don't have an analog meter anymore so I'll just go extra slow.

02-20-2021, 05:13 AM	#11
KivPanther Furball Join Date: Oct 2020 Location: North Carolina Posts: 112 Vehicle: 1994 XE King Cab Thanks: 3 Thanked 21 Times in 18 Posts	With the loose gas cap on the way home I noticed a few things. The stumble didn't go away, but it definitely seemed less intense. It also didn't start doing it until the engine had fully warmed up to operating temperature and only gradually came on once it did. Seems like I might consider replacing the gas cap and cleaning out the filler neck at the very least while hunting for the rest of it. __________________

02-20-2021, 09:18 PM	#12
LugNut1990 Join Date: Jul 2015 Location: N.E. Kansas Posts: 731 Vehicle: 1990 Nissan Hardbody Thanks: 0 Thanked 99 Times in 87 Posts	Interesting! If not a venting problem, next _guess_ is the fuel pump or sock. Before that (PITA job) I'd check out the wiring, grounds, etc. Be careful! __________________ Original owner 1990 Nissan Hardbody, Aztec Red Standard cab, 4x4, KA24E, 5-speed Intentionally near-stock Mods: Second OEM horn, stereo/speakers/sub, mud and snow tires, HD trailer hitch (cat 3+), liquid bed liner, G1W dashcam Definitely not for sale!

02-21-2021, 08:02 PM	#13
KivPanther Furball Join Date: Oct 2020 Location: North Carolina Posts: 112 Vehicle: 1994 XE King Cab Thanks: 3 Thanked 21 Times in 18 Posts	Shall do. I'm also going to run another can of seafoam in the crankcase since I noticed that the rockers and inside of the covers were covered in crud when I replaced the valve cover gaskets. Gotta love farm trucks driven by 90-something year olds! __________________

02-22-2021, 07:13 PM	#14
KivPanther Furball Join Date: Oct 2020 Location: North Carolina Posts: 112 Vehicle: 1994 XE King Cab Thanks: 3 Thanked 21 Times in 18 Posts	I did a quick test on the gas cap valves per the FSM and found out that while the intake is working, the relief is not. So new gas cap anyway. __________________

02-23-2021, 10:08 PM	#16
KivPanther Furball Join Date: Oct 2020 Location: North Carolina Posts: 112 Vehicle: 1994 XE King Cab Thanks: 3 Thanked 21 Times in 18 Posts	I have practically memorized that section of the service manual. I'm still at a loss, hence my request for out-of-box thoughts. __________________

02-23-2021, 08:48 PM	#15
kenmack Join Date: Jan 2015 Location: Edgeoftown Posts: 54 Vehicle: Hardbody 1989 Thanks: 0 Thanked 1 Time in 1 Post	You might consult the factory service manual (FSM) in the EF&EC section which has some good flow charts for servicing. You should start on page EF&EC-45 which will direct you to the flow chart specific to your issue.

02-24-2021, 01:00 AM	#17
Deerhurst 4/86 SE-V6 2 tone 4x4 HB Join Date: Apr 2013 Location: Oregon Posts: 7,388 Vehicle: 1986.5 SE-V6 4WD D21, 2003 Audi A4 Avant 3.0 Quattro Thanks: 892 Thanked 905 Times in 824 Posts	I got 2lbs of tannerite when you are fully fustrated! Got a quick recap of what has been done to job our memories? __________________ 1986.5 SE-V6 4X4 D21 Hardbody Pacesetter Long Tube Headers Morimoto Mini D2S HID Projectors and Hella 500s VG33i

02-24-2021, 07:07 PM	#18
KivPanther Furball Join Date: Oct 2020 Location: North Carolina Posts: 112 Vehicle: 1994 XE King Cab Thanks: 3 Thanked 21 Times in 18 Posts	Sure thing. To date: New distributor New NGK Iridium plugs New NGK plug wires All new injectors and seals Replaced a bunch of vacuum hose and can't find a leak with my current test methods (smoke) New fuel pressure regulator New fuel filter Throttle body cleaned MAF cleaned Throttle Position Sensor tested working Throttle wires adjusted correctly Timing double-checked and steady at 15 BTDC New gas cap New air filter To re-iterate, the stumble does not happen at idle or under full throttle acceleration. It only seems to do it when my foot is barely to lightly on the gas and only between about 2500-3200 RPM. __________________

02-24-2021, 08:58 PM	#19
Deerhurst 4/86 SE-V6 2 tone 4x4 HB Join Date: Apr 2013 Location: Oregon Posts: 7,388 Vehicle: 1986.5 SE-V6 4WD D21, 2003 Audi A4 Avant 3.0 Quattro Thanks: 892 Thanked 905 Times in 824 Posts	Does the TPS have a dead spot? Easiest to see with an analog meter. __________________ 1986.5 SE-V6 4X4 D21 Hardbody Pacesetter Long Tube Headers Morimoto Mini D2S HID Projectors and Hella 500s VG33i

02-25-2021, 04:30 AM	#20
KivPanther Furball Join Date: Oct 2020 Location: North Carolina Posts: 112 Vehicle: 1994 XE King Cab Thanks: 3 Thanked 21 Times in 18 Posts	It seemed steady with my digital meter but I'll double-check. I don't have an analog meter anymore so I'll just go extra slow. __________________

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