RPMS Drop when I lightly touch pedal - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Tankzor01 · 04-22-2016, 03:11 PM

Hey guys,

This is not a recent problem, but it's getting more consistent. From a stop when I lightly touch the gas my rpms drop to around 200 rpm and the engine feels like it's going to stall. This is without letting off the clutch, and also happens in neutral. This causes me to to pop rev my engine or rev it high to take off from a stop. Makes it a pain when in parking lots or in traffic jams.
I'm suspecting the TPS?

HELP ME OUT
s13 sr20

zombiewolf513 · 04-22-2016, 04:31 PM

Are you running a BOV? I had this issue once with a Tial, the BOV was being pulled open. Heavier spring fixed it.

Tankzor01 · 04-22-2016, 07:01 PM

I do run an hks bov, but the problem existed even when I had the stock side mount / bov.

zombiewolf513 · 04-22-2016, 07:31 PM

Okay, i might thoroughly check for cracks in your brake booster hose and other vacuum lines. Especially where the brake booster line makes that 90 degree bend.

Tankzor01 · 04-22-2016, 09:11 PM

Thanks for the help thus far. Did a quick inspection before I drove home from work. Found a split line for the fpr and cut the ends off. Problem still persists.

I was checking all the sensor clips and noticed that the idle drops hard when I even barely touch the throttle cable.

Kingtal0n · 04-23-2016, 02:16 AM

use the oem maf rubber turbo inlet, oem maf sensor, oem style air filter or dry paper element, on the OEM turbo.

boost least test, be sure to test the area between the maf and turbo also, then tune up, oem ecu, oem injectors, clean the injectors/tube/maf (part of tune up)

thats the best it will get. you must not have one or more of these items. What is happening is the air is moving sluggishly because you have altered the inlet path with larger diameter plumbing, slowing velocity and reaction time of the maf hotwire. Either that or it needs cleaning/has a leak, as above, or the fuel pump is weak

xiesteve · 04-23-2016, 05:46 AM

Especially where the brake booster line makes that 90 degree bend.

Tankzor01 · 04-24-2016, 08:33 PM

Ok guys.
Once again thanks for your help thus far.
I did a lot of poking and prodding today and here are my results.
Couldn't find any boost or vac leaks. Boost is steady at 6 psi through powerband.
Vacuum is steady at 19 psi at idle.
Here's my breakthrough. I took a volt meter and everything seemed fine until I got to checking the signal voltage. At idle it reads around .5 volts and wot around 3.5 volts. My problem is, when pulling the throttle back, the voltage increase is not linear. When I lightly touch the throttle the volts spike to 3-4 volts.
So I'm starting to believe I have a bad tps again?
Now I think the TPS is sending a false signal to the ecu, causing the car to run too rich and misfire/bog at low rpm.
Here's a video I took.
Can someone please confirm?
https://youtu.be/z4gaA-CSZdQ

Kingtal0n · 04-25-2016, 02:37 AM

just unplug it. The engine should run pretty normal without one.

they are very cheap so simply replace it if you think its bad.

spimgei · 04-25-2016, 07:16 AM

Either that or it needs cleaning/has a leak, as above, or the fuel pump is weak

04-22-2016, 03:11 PM	#1
Tankzor01 Leaky Injector Join Date: Mar 2012 Location: So cal Age: 37 Posts: 134 Trader Rating: (4) Feedback Score: 4 reviews	RPMS Drop when I lightly touch pedal Hey guys, This is not a recent problem, but it's getting more consistent. From a stop when I lightly touch the gas my rpms drop to around 200 rpm and the engine feels like it's going to stall. This is without letting off the clutch, and also happens in neutral. This causes me to to pop rev my engine or rev it high to take off from a stop. Makes it a pain when in parking lots or in traffic jams. I'm suspecting the TPS? HELP ME OUT s13 sr20

04-24-2016, 08:33 PM	#8
Tankzor01 Leaky Injector Join Date: Mar 2012 Location: So cal Age: 37 Posts: 134 Trader Rating: (4) Feedback Score: 4 reviews	Bump Ok guys. Once again thanks for your help thus far. I did a lot of poking and prodding today and here are my results. Couldn't find any boost or vac leaks. Boost is steady at 6 psi through powerband. Vacuum is steady at 19 psi at idle. Here's my breakthrough. I took a volt meter and everything seemed fine until I got to checking the signal voltage. At idle it reads around .5 volts and wot around 3.5 volts. My problem is, when pulling the throttle back, the voltage increase is not linear. When I lightly touch the throttle the volts spike to 3-4 volts. So I'm starting to believe I have a bad tps again? Now I think the TPS is sending a false signal to the ecu, causing the car to run too rich and misfire/bog at low rpm. Here's a video I took. Can someone please confirm? https://youtu.be/z4gaA-CSZdQ

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04-22-2016, 04:31 PM	#2
zombiewolf513 BANNED Join Date: Mar 2011 Location: AZ Age: 36 Posts: 1,682 Trader Rating: (6) Rides Gallery: zombiewolf513 Feedback Score: 6 reviews	Are you running a BOV? I had this issue once with a Tial, the BOV was being pulled open. Heavier spring fixed it.

04-22-2016, 07:01 PM	#3
Tankzor01 Leaky Injector Join Date: Mar 2012 Location: So cal Age: 37 Posts: 134 Trader Rating: (4) Feedback Score: 4 reviews	I do run an hks bov, but the problem existed even when I had the stock side mount / bov.

04-22-2016, 07:31 PM	#4
zombiewolf513 BANNED Join Date: Mar 2011 Location: AZ Age: 36 Posts: 1,682 Trader Rating: (6) Rides Gallery: zombiewolf513 Feedback Score: 6 reviews	Okay, i might thoroughly check for cracks in your brake booster hose and other vacuum lines. Especially where the brake booster line makes that 90 degree bend.

04-22-2016, 09:11 PM	#5
Tankzor01 Leaky Injector Join Date: Mar 2012 Location: So cal Age: 37 Posts: 134 Trader Rating: (4) Feedback Score: 4 reviews	Thanks for the help thus far. Did a quick inspection before I drove home from work. Found a split line for the fpr and cut the ends off. Problem still persists. I was checking all the sensor clips and noticed that the idle drops hard when I even barely touch the throttle cable.

04-23-2016, 02:16 AM	#6
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,828 Trader Rating: (17) Feedback Score: 17 reviews	use the oem maf rubber turbo inlet, oem maf sensor, oem style air filter or dry paper element, on the OEM turbo. boost least test, be sure to test the area between the maf and turbo also, then tune up, oem ecu, oem injectors, clean the injectors/tube/maf (part of tune up) thats the best it will get. you must not have one or more of these items. What is happening is the air is moving sluggishly because you have altered the inlet path with larger diameter plumbing, slowing velocity and reaction time of the maf hotwire. Either that or it needs cleaning/has a leak, as above, or the fuel pump is weak

04-23-2016, 05:46 AM	#7
xiesteve Join Date: Apr 2016 Location: CA Age: 38 Posts: 3 Trader Rating: (0) Feedback Score: 0 reviews	Especially where the brake booster line makes that 90 degree bend.

04-25-2016, 02:37 AM	#9
Kingtal0n Post Whore! Join Date: Jul 2005 Location: South Florida Age: 41 Posts: 4,828 Trader Rating: (17) Feedback Score: 17 reviews	just unplug it. The engine should run pretty normal without one. they are very cheap so simply replace it if you think its bad.

04-25-2016, 07:16 AM	#10
spimgei Join Date: Apr 2016 Location: CA Age: 39 Posts: 2 Trader Rating: (0) Feedback Score: 0 reviews	Either that or it needs cleaning/has a leak, as above, or the fuel pump is weak