sr20det startup 4k idle then rpm climbs - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

taritte · 08-13-2013, 11:42 AM

Whats up guys, I've searched and searched but still haven't found an answer. The car is a 1990 s13 with a redtop sr with basic bolt ons. As i was driving i pulled out into traffic (built about 5psi and when i let off the rpm hung around 4k+ rpm. Also I didnt have brake pressure. When in gear and slowing down the vac goes to 0 causing the loss of brake pressure. The problem is when I start the car the rpms shoot straight to 4k then after the rpms just keep going up until I turn the car off. I've checked vac lines and couplers for a leak with no luck. I've also took off the vac line to bov still no change, unplugged maf idles low and dies, unhooked the iacv no change, unhooked tps no change no codes are being thrown and gas pedal/cable isnt hung up.I'm completely stumped I've tried everything that I can think of. I'd really appreciate any ideas or tips, its my dd so its really stressing me out.

Thanks for any input.

codyace · 08-13-2013, 02:39 PM

For it to rev up to 4k without worry something must be snagging it or a huge vacuum leak. Is timing set?

taritte · 08-13-2013, 05:04 PM

The timing hasnt been messed with in over a year and this is the first problem I've had. But everything seems to look the same as when It ran good. I've checked vac lines and unhooking some to give it a boost leak with no difference so it makes me think the problem is behind the throttle body but I'm new to sr20s so that's just a guess.

Howard Smith · 08-13-2013, 05:55 PM

There should be a check valve inline on the vacuum line to the brake booster. It may be bad. take it out and blow into each end. Air should go in one direction only. Could be the source of the vacuum leak.

Also check the IACV line from the intake pipe and the IACV itself. They get dirty and hang up.

taritte · 08-14-2013, 03:21 PM

Ok so I took off and cleaned the iacv still revs up when I start it. I checked the valve in between the brake booster and the manifold, completely blocked off the brake booster and still. So I guess next ill try blocking the throttle body listen for leaks then take off the manifold.. i shouldve bought a camry :/

Howard Smith · 08-14-2013, 09:32 PM

Start it, let it idle then turn the screw all the way in on the IACV. If it still idles high there is air getting in somewhere. Check that the throttle body is closing all the way and not hitting the set screw.

Howard Smith · 08-14-2013, 09:33 PM

PS Don't give up. It will be worth the trouble when it's right. 240's are a blast! a pain in the ass but when they are right they are a lot of fun.

codyace · 08-14-2013, 10:11 PM

If it ran before just fine, I'd really look into a severe vacuum leak.

taritte · 08-16-2013, 10:02 PM

Good news the cars all back together and running normal. Of course it was something simple to make me feel completely stupid. When I took off the throttle body and when I looked it over the tps tab was under the throttle plate keeping the tb open. . I guess the tps wasnt fitted right so it slipped off under throttle. Definitely one of those slap in the face moments.

Thanks guys for all your help I really appreciate it.

08-13-2013, 11:42 AM	#1
taritte Join Date: Aug 2013 Location: colorado springs Age: 32 Posts: 5 Trader Rating: (0) Feedback Score: 0 reviews	sr20det startup 4k idle then rpm climbs Whats up guys, I've searched and searched but still haven't found an answer. The car is a 1990 s13 with a redtop sr with basic bolt ons. As i was driving i pulled out into traffic (built about 5psi and when i let off the rpm hung around 4k+ rpm. Also I didnt have brake pressure. When in gear and slowing down the vac goes to 0 causing the loss of brake pressure. The problem is when I start the car the rpms shoot straight to 4k then after the rpms just keep going up until I turn the car off. I've checked vac lines and couplers for a leak with no luck. I've also took off the vac line to bov still no change, unplugged maf idles low and dies, unhooked the iacv no change, unhooked tps no change no codes are being thrown and gas pedal/cable isnt hung up.I'm completely stumped I've tried everything that I can think of. I'd really appreciate any ideas or tips, its my dd so its really stressing me out. Thanks for any input.

08-13-2013, 02:39 PM	#2
codyace Post Whore! Join Date: Dec 2004 Location: Poconos, PA Age: 40 Posts: 8,030 Trader Rating: (58) Feedback Score: 58 reviews	For it to rev up to 4k without worry something must be snagging it or a huge vacuum leak. Is timing set? __________________ *Want Air Conditioning in your SR20 Swapped car? Check out www.sr20acbrackets.com for more information! Quest Alternator Conversions for SR20!* Check my Group Buy! Tired of lousy internal gates? Go external wastegate with one of my manifolds, Check out my group buy

08-13-2013, 05:55 PM	#4
Howard Smith Join Date: Aug 2013 Location: Georgia Posts: 9 Trader Rating: (0) Feedback Score: 0 reviews	There should be a check valve inline on the vacuum line to the brake booster. It may be bad. take it out and blow into each end. Air should go in one direction only. Could be the source of the vacuum leak. Also check the IACV line from the intake pipe and the IACV itself. They get dirty and hang up. __________________ Smoke tires, not tobacco!

08-14-2013, 09:32 PM	#6
Howard Smith Join Date: Aug 2013 Location: Georgia Posts: 9 Trader Rating: (0) Feedback Score: 0 reviews	Start it, let it idle then turn the screw all the way in on the IACV. If it still idles high there is air getting in somewhere. Check that the throttle body is closing all the way and not hitting the set screw. __________________ Smoke tires, not tobacco!

08-14-2013, 09:33 PM	#7
Howard Smith Join Date: Aug 2013 Location: Georgia Posts: 9 Trader Rating: (0) Feedback Score: 0 reviews	PS Don't give up. It will be worth the trouble when it's right. 240's are a blast! a pain in the ass but when they are right they are a lot of fun. __________________ Smoke tires, not tobacco!

08-13-2013, 05:04 PM	#3
taritte Join Date: Aug 2013 Location: colorado springs Age: 32 Posts: 5 Trader Rating: (0) Feedback Score: 0 reviews	The timing hasnt been messed with in over a year and this is the first problem I've had. But everything seems to look the same as when It ran good. I've checked vac lines and unhooking some to give it a boost leak with no difference so it makes me think the problem is behind the throttle body but I'm new to sr20s so that's just a guess.

08-14-2013, 03:21 PM	#5
taritte Join Date: Aug 2013 Location: colorado springs Age: 32 Posts: 5 Trader Rating: (0) Feedback Score: 0 reviews	Ok so I took off and cleaned the iacv still revs up when I start it. I checked the valve in between the brake booster and the manifold, completely blocked off the brake booster and still. So I guess next ill try blocking the throttle body listen for leaks then take off the manifold.. i shouldve bought a camry :/

08-14-2013, 10:11 PM	#8
codyace Post Whore! Join Date: Dec 2004 Location: Poconos, PA Age: 40 Posts: 8,030 Trader Rating: (58) Feedback Score: 58 reviews	If it ran before just fine, I'd really look into a severe vacuum leak. __________________ *Want Air Conditioning in your SR20 Swapped car? Check out www.sr20acbrackets.com for more information! Quest Alternator Conversions for SR20!* Check my Group Buy! Tired of lousy internal gates? Go external wastegate with one of my manifolds, Check out my group buy

08-16-2013, 10:02 PM	#9
taritte Join Date: Aug 2013 Location: colorado springs Age: 32 Posts: 5 Trader Rating: (0) Feedback Score: 0 reviews	Good news the cars all back together and running normal. Of course it was something simple to make me feel completely stupid. When I took off the throttle body and when I looked it over the tps tab was under the throttle plate keeping the tb open. . I guess the tps wasnt fitted right so it slipped off under throttle. Definitely one of those slap in the face moments. Thanks guys for all your help I really appreciate it.