SR20det boost or bog issues past 3500k - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

TheVinylKingz · 04-05-2021, 10:29 AM

S13 hatch with SR20DET after driving for approximately 10-15 min motor starts to sounds like it?s running on 3 cylinders and doesn?t boost past 3.5RPM... it?s happened a few times. When on cold start or approximately under 10-15 min of driving it starts acting up, every single time.

I have checked spark plugs and there doesn?t appear to be a exhaust leak on the manifold.

It?s a rebuilt motor and I don?t push it or drift. Approximately 2500k miles on new rebuilt motor.

Any suggestions?????

Silv1401 · 04-05-2021, 10:59 AM

Does it bog no matter what past 3,500rpm? Like if you just tiptoe up the revs and stay out of boost can you get past 3,500?

My immediate impression would be a boost/vac leak. Check all of your couplers, and vac lines for tightness/cracks. I always have rough luck find leaks so I usually just take it to a place with a smoker to make life easier and give me a definitive yes/no answer. Because some boost leaks won't always be a vac leak as well, and they will only crack open at say 4psi, acting like a small wastegate.

If it's a consistent bogging at 3,500rpm regardless of boost, I would say it's probably a fuel issue. Not getting enough pressure or volume. Not sure what kind of mods you have, maybe your fuel pump is on its way out, or your filter is clogged af.

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TheVinylKingz · 04-05-2021, 12:46 PM

This issue happens randomly and it loses power. When I give it gas it starts resisting on the pedal as I try to rev up while driving, trying to boost.. Also at a stand still it’s the same. It’s like as if it’s on a switch it began to do this.

Silv1401 · 04-05-2021, 12:51 PM

So sometimes you can hit boost and other times your can't? Or sometimes you can go above 3500rpm so long as you stay out of boost?

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TheVinylKingz · 04-05-2021, 01:37 PM

I can?t hit boost when this happens. I?m stuck even at a stand still I hear the motor sounding like it?s on 3 cylinders. Weird. It?s good for a few miles or under 10-15 min of driving, but then it just stops operating like it should.

Mods: Tomei pon cams, 86.5 mm pistons, stock side Mount, stock ECU, new walbro fuel pump 255, z32 fuel filter, stock MAF, and the at about it major Bolton?s... stock injectors.

Quote:

Originally Posted by Silv1401

So sometimes you can hit boost and other times your can't? Or sometimes you can go above 3500rpm so long as you stay out of boost?

Sent from my SM-N986U1 using Tapatalk

Kingtal0n · 04-05-2021, 07:39 PM

you need to perform a pressure test and get a wideband

Thursday7 · 04-06-2021, 05:33 AM

hook an air compressor to the intake side of your turbo, turn the regulator to ~10psi and pressurize the system. Then start going ham with a spray bottle of soapy water on all vac hoses, couplers, connections, etc, looking for bubbles.

Test the resistance in your maf or try a known good one.

Get a wideband.

Backprobe and test the voltage on your TPS

Kingtal0n · 04-06-2021, 06:03 PM

make sure to disconnect the crankcase vent tube for pressure testing.
I would also remove the dip stick and oil cap. Maybe just loosen the oil cap at least.

If you accidentally pressurize the crankcase in the process you could blow out the oil seals.

Also during the pressure test, you can listen to the dipstick and oil cap hole to hear air leaking past the piston rings (like a pseudo leak down test)
this is also a great time to test the pcv valve and I would also replace it (replace and make sure the new one works)

04-05-2021, 10:29 AM	#1
TheVinylKingz Leaky Injector Join Date: Mar 2011 Location: Los Angeles Posts: 97 Trader Rating: (0) Feedback Score: 0 reviews	SR20det boost or bog issues past 3500k S13 hatch with SR20DET after driving for approximately 10-15 min motor starts to sounds like it?s running on 3 cylinders and doesn?t boost past 3.5RPM... it?s happened a few times. When on cold start or approximately under 10-15 min of driving it starts acting up, every single time. I have checked spark plugs and there doesn?t appear to be a exhaust leak on the manifold. It?s a rebuilt motor and I don?t push it or drift. Approximately 2500k miles on new rebuilt motor. Any suggestions????? __________________ S13 SR, S14 KA

04-05-2021, 12:46 PM	#3
TheVinylKingz Leaky Injector Join Date: Mar 2011 Location: Los Angeles Posts: 97 Trader Rating: (0) Feedback Score: 0 reviews	This issue happens randomly and it loses power. When I give it gas it starts resisting on the pedal as I try to rev up while driving, trying to boost.. Also at a stand still it’s the same. It’s like as if it’s on a switch it began to do this. __________________ S13 SR, S14 KA

04-05-2021, 10:59 AM	#2
Silv1401 Zilvia Member Join Date: Jan 2019 Location: Vancouver, WA/Portland, OR, USA Posts: 189 Trader Rating: (1) Feedback Score: 1 reviews	Does it bog no matter what past 3,500rpm? Like if you just tiptoe up the revs and stay out of boost can you get past 3,500? My immediate impression would be a boost/vac leak. Check all of your couplers, and vac lines for tightness/cracks. I always have rough luck find leaks so I usually just take it to a place with a smoker to make life easier and give me a definitive yes/no answer. Because some boost leaks won't always be a vac leak as well, and they will only crack open at say 4psi, acting like a small wastegate. If it's a consistent bogging at 3,500rpm regardless of boost, I would say it's probably a fuel issue. Not getting enough pressure or volume. Not sure what kind of mods you have, maybe your fuel pump is on its way out, or your filter is clogged af. Sent from my SM-N986U1 using Tapatalk

04-05-2021, 12:51 PM	#4
Silv1401 Zilvia Member Join Date: Jan 2019 Location: Vancouver, WA/Portland, OR, USA Posts: 189 Trader Rating: (1) Feedback Score: 1 reviews	So sometimes you can hit boost and other times your can't? Or sometimes you can go above 3500rpm so long as you stay out of boost? Sent from my SM-N986U1 using Tapatalk

04-05-2021, 07:39 PM	#6
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,828 Trader Rating: (17) Feedback Score: 17 reviews	you need to perform a pressure test and get a wideband

04-06-2021, 05:33 AM	#7
Thursday7 Zilvia Addict Join Date: Jul 2011 Location: PA Posts: 800 Trader Rating: (8) Feedback Score: 8 reviews	hook an air compressor to the intake side of your turbo, turn the regulator to ~10psi and pressurize the system. Then start going ham with a spray bottle of soapy water on all vac hoses, couplers, connections, etc, looking for bubbles. Test the resistance in your maf or try a known good one. Get a wideband. Backprobe and test the voltage on your TPS

04-06-2021, 06:03 PM	#8
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,828 Trader Rating: (17) Feedback Score: 17 reviews	make sure to disconnect the crankcase vent tube for pressure testing. I would also remove the dip stick and oil cap. Maybe just loosen the oil cap at least. If you accidentally pressurize the crankcase in the process you could blow out the oil seals. Also during the pressure test, you can listen to the dipstick and oil cap hole to hear air leaking past the piston rings (like a pseudo leak down test) this is also a great time to test the pcv valve and I would also replace it (replace and make sure the new one works)