SR20DET Miss Fire\Bucking - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Engmus · 01-20-2019, 01:27 PM

Hey Guys, looking for some opinions as these things are always hard to troubleshoot over the interbutts.

91 240sx\SR20 Blacktop Swap

Issue: Car bucks\misses after warming up at highway speeds. Feels like a misfire, although happens really sporadically.

Troubleshooting thus far:

TPS Reset - Good
New Fuel Filter - Good
New Spark Plugs - Good
Throttle Body\IACV Cleaned - Good
New Walbro 255 Fuel Pump - Good
Vacuum leaks - None detectable at this point, will continue to look.
Repinned CAS sensor wiring and replaced harness side plug - Good

I suspect at this point Cam Angle Sensor faulty or Igniter Faulty.

Anyone have any ideas? Things to check?

Coupes_FTW · 01-20-2019, 01:40 PM

sounds like a dying coilpack

Engmus · 01-20-2019, 01:41 PM

5k Miles ago I installed a set of SplitFire Coils, I have spare Splitfire Coil packs.

Coupes_FTW · 01-20-2019, 01:48 PM

clean the MAF sensor

jdmgtom · 01-20-2019, 02:00 PM

I had a similar problem, I think your next best thing to do is replace your ignition coils if you haven't already recently. I just bought a set of p2m's ignition coils for $140... very worth.
Also this is a long shot, but maybe check your brake calipers to see if they're sticking to the rotor, because that would make it feel like theres a boost leak or a misfire if its sticking bad. happened to me..

Kingtal0n · 01-20-2019, 03:59 PM

What does wideband say during problems?

A misfire will show up on the wideband usually and verify it is actually a misfire

frsh2fourty · 01-21-2019, 09:32 AM

Check your injectors. You might have one that is slowly starting to fail. You can do it with a multimeter, I forget what the resistance is supposed to read but they should all read about the same if they are all good so a bad one will be really apparent. I had one that was intermittently sticking closed and the reading was still way off even though it wasn't completely bad.

Engmus · 01-22-2019, 05:58 AM

Thanks for the ideas guys.

I cleaned my MAF and had no change, tested maf and it looks good.

This weekend i'll try swapping Coils, and check injectors.

I'll report back with my resolution when known.

z31andrew · 01-22-2019, 10:05 AM

If your car is tuned check your rom chip. The same shit was happening on my car, I have solid mounts so the chip actually vibrated out of the ECU and was causing a faulty connection, my car would buck like crazy but idles no problem.I tried swapping MAFs, coils, plugs, etc just to find it was the damn chip.

RomulanS13 · 01-23-2019, 02:48 PM

I had a really bad miss fire under load and if boost hit anything over 4psi. I replaced alt, coil packs, re did grounds, re installed CAS, adjusted TPS to factory spec and none of that worked. I Previously when first swapped the sr gapped the plugs to .028 or around that tried gapping them wider and the problem got even worse so I re gapped around .025 and all boost problems under load freeway speeds are gone no bucking or miss fire. something that simple haunted me for months until now. Hope that helps.

ultimateirving · 01-24-2019, 11:32 AM

Check grounds.

I had the one on the back of the head wiggle loose. Like mentioned above, sounds like coilpacks

jedi03 · 01-28-2019, 12:21 PM

also if theres oil pooling by the coils can cause same issue...replace vavle cover gasket

Engmus · 03-08-2019, 06:50 AM

I wanted to follow up on this, my problem was my TPS.

Even though the TPS would set voltage correctly, as you opened the Throttle the voltage was all over the place, sometimes it would be fine, othertimes it would be really bad.

I replaced the TPS with a genuine unit from Nissan. Moral of the story...

Just because you check voltage on the sensor at idle, doesn't mean that as you drive the vehicle it isn't a problem, it could be somewhere between totally rekt and on the way out.

Thanks all for the input and great ideas.

01-20-2019, 01:27 PM	#1
Engmus Leaky Injector Join Date: Mar 2016 Location: PA Age: 33 Posts: 104 Trader Rating: (1) Feedback Score: 1 reviews	SR20DET Miss Fire\Bucking Hey Guys, looking for some opinions as these things are always hard to troubleshoot over the interbutts. 91 240sx\SR20 Blacktop Swap Issue: Car bucks\misses after warming up at highway speeds. Feels like a misfire, although happens really sporadically. Troubleshooting thus far: TPS Reset - Good New Fuel Filter - Good New Spark Plugs - Good Throttle Body\IACV Cleaned - Good New Walbro 255 Fuel Pump - Good Vacuum leaks - None detectable at this point, will continue to look. Repinned CAS sensor wiring and replaced harness side plug - Good I suspect at this point Cam Angle Sensor faulty or Igniter Faulty. Anyone have any ideas? Things to check?

01-24-2019, 11:32 AM	#11
ultimateirving Zilvia FREAK! Join Date: Nov 2010 Location: arizona Age: 33 Posts: 1,519 Trader Rating: (1) Feedback Score: 1 reviews	Check grounds. I had the one on the back of the head wiggle loose. Like mentioned above, sounds like coilpacks __________________ Z32 with lq4 swap Desert Street Scene \|\| Dssevents.com

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01-20-2019, 01:40 PM	#2
Coupes_FTW Leaky Injector Join Date: Aug 2008 Location: Beaverton Posts: 103 Trader Rating: (2) Feedback Score: 2 reviews	sounds like a dying coilpack

01-20-2019, 01:41 PM	#3
Engmus Leaky Injector Join Date: Mar 2016 Location: PA Age: 33 Posts: 104 Trader Rating: (1) Feedback Score: 1 reviews	5k Miles ago I installed a set of SplitFire Coils, I have spare Splitfire Coil packs.

01-20-2019, 01:48 PM	#4
Coupes_FTW Leaky Injector Join Date: Aug 2008 Location: Beaverton Posts: 103 Trader Rating: (2) Feedback Score: 2 reviews	clean the MAF sensor

01-20-2019, 02:00 PM	#5
jdmgtom Leaky Injector Join Date: Aug 2018 Location: St. Petersburg, FL Age: 28 Posts: 147 Trader Rating: (0) Feedback Score: 0 reviews	I had a similar problem, I think your next best thing to do is replace your ignition coils if you haven't already recently. I just bought a set of p2m's ignition coils for $140... very worth. Also this is a long shot, but maybe check your brake calipers to see if they're sticking to the rotor, because that would make it feel like theres a boost leak or a misfire if its sticking bad. happened to me..

01-20-2019, 03:59 PM	#6
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 38 Posts: 4,649 Trader Rating: (17) Feedback Score: 17 reviews	What does wideband say during problems? A misfire will show up on the wideband usually and verify it is actually a misfire

01-21-2019, 09:32 AM	#7
frsh2fourty Join Date: Jan 2007 Location: Houston, Texas Age: 31 Posts: 49 Trader Rating: (0) Feedback Score: 0 reviews	Check your injectors. You might have one that is slowly starting to fail. You can do it with a multimeter, I forget what the resistance is supposed to read but they should all read about the same if they are all good so a bad one will be really apparent. I had one that was intermittently sticking closed and the reading was still way off even though it wasn't completely bad.

01-22-2019, 05:58 AM	#8
Engmus Leaky Injector Join Date: Mar 2016 Location: PA Age: 33 Posts: 104 Trader Rating: (1) Feedback Score: 1 reviews	Thanks for the ideas guys. I cleaned my MAF and had no change, tested maf and it looks good. This weekend i'll try swapping Coils, and check injectors. I'll report back with my resolution when known.

01-22-2019, 10:05 AM	#9
z31andrew Zilvia Member Join Date: Aug 2016 Location: Orange, CA Age: 27 Posts: 176 Trader Rating: (5) Feedback Score: 5 reviews	If your car is tuned check your rom chip. The same shit was happening on my car, I have solid mounts so the chip actually vibrated out of the ECU and was causing a faulty connection, my car would buck like crazy but idles no problem.I tried swapping MAFs, coils, plugs, etc just to find it was the damn chip.

01-23-2019, 02:48 PM	#10
RomulanS13 Join Date: Oct 2017 Location: near salty oceans Posts: 30 Trader Rating: (0) Feedback Score: 0 reviews	I had a really bad miss fire under load and if boost hit anything over 4psi. I replaced alt, coil packs, re did grounds, re installed CAS, adjusted TPS to factory spec and none of that worked. I Previously when first swapped the sr gapped the plugs to .028 or around that tried gapping them wider and the problem got even worse so I re gapped around .025 and all boost problems under load freeway speeds are gone no bucking or miss fire. something that simple haunted me for months until now. Hope that helps.

01-28-2019, 12:21 PM	#12
jedi03 Nissanaholic! Join Date: Jul 2008 Location: albuquerque Posts: 1,784 Trader Rating: (8) Feedback Score: 8 reviews	also if theres oil pooling by the coils can cause same issue...replace vavle cover gasket

03-08-2019, 06:50 AM	#13
Engmus Leaky Injector Join Date: Mar 2016 Location: PA Age: 33 Posts: 104 Trader Rating: (1) Feedback Score: 1 reviews	I wanted to follow up on this, my problem was my TPS. Even though the TPS would set voltage correctly, as you opened the Throttle the voltage was all over the place, sometimes it would be fine, othertimes it would be really bad. I replaced the TPS with a genuine unit from Nissan. Moral of the story... Just because you check voltage on the sensor at idle, doesn't mean that as you drive the vehicle it isn't a problem, it could be somewhere between totally rekt and on the way out. Thanks all for the input and great ideas.