Car seems to be down on power, where to start looking? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

alkemyst · 05-22-2008, 05:34 PM

I have new plugs (NGK Vpower), wires, injectors (stock 270cc), fuel filter, exhaust and hi flow cat, header, did the 248/232 cam swap (248 is +2.5 adv), injen intake.

Car doesn't seem like it wants to launch hard...anything I can look at for the 'tune'.

Timing is at 20BTDC. I have a OBDII reader that can check O2 volts, temps, etc.

The clutch doesn't seem to be slipping.

I am curious to the O2 sensors...my MPG (mostly city about 5 miles back and forth to work) is only 16-18MPG.

Here is a data dump.

Calculated Load: 24.7%
Coolant Temp: 171F
Short Term Fuel Trim B1: -5.65%
Long Term Fuel Trim B1: 2.3%
Manifold Pressure: 9.8 inHg
Engine RPM: 1000 (788 without A/C on)
Ignition Advance: 20deg
Intake Air Temp: 117F
Air Flow: 0.7 lb/m
O2 B1,S1: 60-800 mV
O2 B1,S1(Fuel Trim): -3 to -7 %
O2 B1,S2: 680-740 mV
O2 B1,S2(Fuel Trim): 99.2%

Thanks

Å

Mikey213 · 05-23-2008, 03:18 PM

Try.a.lighter.flywheel.and.a.LSD/welded

alkemyst · 05-23-2008, 08:51 PM

have the lsd...wasn't looking to keep trying though. A lighter flywheel should always help, but is probably not a solution to a problem.

I am thinking although my clutch isn't slipping that I can see it probably is.

LA_phantom_240 · 05-23-2008, 08:54 PM

Doesn't launch hard? Look at motor/tranny mounts. Mine are toast, and it lurches....

infinitexsound · 05-24-2008, 01:29 AM

i honestly dont understand if your trying to produce more power or trying to solve a mechanical issue.....

tt99ol · 05-24-2008, 02:58 AM

your vacuum is at 9.8 inHg at idle?
that cant be right
those cams aren't big enough to cause that
maybe vacuum leak

SoguRacing · 05-24-2008, 03:46 AM

manifold "vacuum" at idle should be 17-21 inches of mercury. yours says pressure so that would be negative 9.8 right? bad intake valves/vacuum leak? your short term fuel trim is rich that's why your short term fuel trim is -5.% you want those to hover around zero. O2 B1,S2: 680-740 mV i think bank 1 sensor 2 is bad. it should read min voltage of <200mv - >800mv but less than 1 volt. your range is way off thus your ecu is getting a mis calibrated signal and making you run rich.

DudeYourSoOOJDM · 05-24-2008, 04:14 AM

Compression test?

ngibson · 05-24-2008, 08:53 AM

Check your ground connections as well. I had a problem with low end big time, it would hesitate like all hell then pull like mad. Turned out the ground connection to the chassis from the negative terminal of the battery was very corroded - a quick check with an ohm-meter showed it had very high resistance.

alkemyst · 05-24-2008, 08:09 PM

Quote:

Originally Posted by LA_phantom_240

Doesn't launch hard? Look at motor/tranny mounts. Mine are toast, and it lurches....

New nismo motor and trans mounts.

Quote:

Originally Posted by ngibson

Check your ground connections as well. I had a problem with low end big time, it would hesitate like all hell then pull like mad. Turned out the ground connection to the chassis from the negative terminal of the battery was very corroded - a quick check with an ohm-meter showed it had very high resistance.

I will check that...I upgraded the grounds, but you never know...

Where to you check at ground point and battery neg post?

Quote:

Originally Posted by DudeYourSoOOJDM

Compression test?

did that 175 on all 4.

koukimonster139 · 05-24-2008, 08:14 PM

seems like its running too rich when you dump it and then clearing out after it starts revving

whats fuel pressure like?

alkemyst · 05-24-2008, 08:15 PM

Quote:

Originally Posted by SoguRacing

manifold "vacuum" at idle should be 17-21 inches of mercury. yours says pressure so that would be negative 9.8 right? bad intake valves/vacuum leak? your short term fuel trim is rich that's why your short term fuel trim is -5.% you want those to hover around zero. O2 B1,S2: 680-740 mV i think bank 1 sensor 2 is bad. it should read min voltage of <200mv - >800mv but less than 1 volt. your range is way off thus your ecu is getting a mis calibrated signal and making you run rich.

I didn't check the O2 S2 actively like the S1...I thought the S2 was only used to check if the cat was good and not for any ECU changes.

The OBDII shows Manifold Pressure inHg...it's not shown as a negative number. I checked again and some cars show 9.8inHg at idle would be normal. I will recheck and use my brakes to see if this number changes properly.

If it is a vacuum leak, where do I start looking?

alkemyst · 05-25-2008, 09:56 AM

I can't find the info on how much the brake booster should affect manifold pressure.

Mine was 10.1 inHG today and went up to 11.5ish when I release the brakes and then back down.

05-22-2008, 05:34 PM	#1
alkemyst Zilvia Addict Join Date: Oct 2003 Location: Florida Age: 53 Posts: 868 Trader Rating: (0) Feedback Score: 0 reviews	Car seems to be down on power, where to start looking? I have new plugs (NGK Vpower), wires, injectors (stock 270cc), fuel filter, exhaust and hi flow cat, header, did the 248/232 cam swap (248 is +2.5 adv), injen intake. Car doesn't seem like it wants to launch hard...anything I can look at for the 'tune'. Timing is at 20BTDC. I have a OBDII reader that can check O2 volts, temps, etc. The clutch doesn't seem to be slipping. I am curious to the O2 sensors...my MPG (mostly city about 5 miles back and forth to work) is only 16-18MPG. Here is a data dump. Calculated Load: 24.7% Coolant Temp: 171F Short Term Fuel Trim B1: -5.65% Long Term Fuel Trim B1: 2.3% Manifold Pressure: 9.8 inHg Engine RPM: 1000 (788 without A/C on) Ignition Advance: 20deg Intake Air Temp: 117F Air Flow: 0.7 lb/m O2 B1,S1: 60-800 mV O2 B1,S1(Fuel Trim): -3 to -7 % O2 B1,S2: 680-740 mV O2 B1,S2(Fuel Trim): 99.2% Thanks Å __________________ Now my Kensai, I curse you to be a Ronin and with the my remaining spirit I, beseech Chimata-No-Kami, to have you wander through time and distance lands, seeking a new master. Last edited by alkemyst; 05-22-2008 at 06:31 PM..

05-23-2008, 08:51 PM	#3
alkemyst Zilvia Addict Join Date: Oct 2003 Location: Florida Age: 53 Posts: 868 Trader Rating: (0) Feedback Score: 0 reviews	have the lsd...wasn't looking to keep trying though. A lighter flywheel should always help, but is probably not a solution to a problem. I am thinking although my clutch isn't slipping that I can see it probably is. __________________ Now my Kensai, I curse you to be a Ronin and with the my remaining spirit I, beseech Chimata-No-Kami, to have you wander through time and distance lands, seeking a new master.

05-24-2008, 01:29 AM	#5
infinitexsound Post Whore! Join Date: Sep 2003 Location: INtraweb Age: 42 Posts: 3,522 Trader Rating: (0) Feedback Score: 0 reviews	i honestly dont understand if your trying to produce more power or trying to solve a mechanical issue..... __________________ S14 TrackSlut coming to a raceway near you... 510 TimeAttack on its way...

05-24-2008, 02:58 AM	#6
tt99ol Zilvia Addict Join Date: Jan 2005 Location: quartz hill CA Age: 38 Posts: 644 Trader Rating: (8) Feedback Score: 8 reviews	your vacuum is at 9.8 inHg at idle? that cant be right those cams aren't big enough to cause that maybe vacuum leak __________________ Need automotive work done in the antelope valley? Ask me how i can help.

05-24-2008, 03:46 AM	#7
SoguRacing Post Whore! Join Date: Nov 2007 Location: (714) Age: 39 Posts: 2,967 Trader Rating: (23) Rides Gallery: SoguRacing Feedback Score: 23 reviews	manifold "vacuum" at idle should be 17-21 inches of mercury. yours says pressure so that would be negative 9.8 right? bad intake valves/vacuum leak? your short term fuel trim is rich that's why your short term fuel trim is -5.% you want those to hover around zero. O2 B1,S2: 680-740 mV i think bank 1 sensor 2 is bad. it should read min voltage of <200mv - >800mv but less than 1 volt. your range is way off thus your ecu is getting a mis calibrated signal and making you run rich. __________________ Pre Tune Checkup! Compression,LeakDown,Vacuum Test $80. Cams Install: $180

05-23-2008, 03:18 PM	#2
Mikey213 Zilvia Junkie Join Date: Oct 2007 Location: Los Angeles Age: 39 Posts: 503 Trader Rating: (-1) Feedback Score: -1 reviews	Try.a.lighter.flywheel.and.a.LSD/welded

05-24-2008, 04:14 AM	#8
DudeYourSoOOJDM Zilvia Junkie Join Date: Jan 2003 Location: Palmdale CA Age: 42 Posts: 479 Trader Rating: (0) Feedback Score: 0 reviews	Compression test? __________________ Since 2001.

05-24-2008, 08:53 AM	#9
ngibson Zilvia Member Join Date: Dec 2007 Location: FL Age: 37 Posts: 150 Trader Rating: (5) Feedback Score: 5 reviews	Check your ground connections as well. I had a problem with low end big time, it would hesitate like all hell then pull like mad. Turned out the ground connection to the chassis from the negative terminal of the battery was very corroded - a quick check with an ohm-meter showed it had very high resistance.

05-24-2008, 08:14 PM	#11
koukimonster139 Zilvia FREAK! Join Date: Jan 2006 Location: Birmingham, AL Age: 38 Posts: 1,379 Trader Rating: (0) Feedback Score: 0 reviews	seems like its running too rich when you dump it and then clearing out after it starts revving whats fuel pressure like? __________________ ho ha ho chi chi

05-25-2008, 09:56 AM	#13
alkemyst Zilvia Addict Join Date: Oct 2003 Location: Florida Age: 53 Posts: 868 Trader Rating: (0) Feedback Score: 0 reviews	I can't find the info on how much the brake booster should affect manifold pressure. Mine was 10.1 inHG today and went up to 11.5ish when I release the brakes and then back down. __________________ Now my Kensai, I curse you to be a Ronin and with the my remaining spirit I, beseech Chimata-No-Kami, to have you wander through time and distance lands, seeking a new master.