installed intake manifold, car now idles poorly - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

*niSm095* · 06-06-2009, 08:20 PM

Today I swapped out the stock SR intake manifold for a custom made aluminum piece...very good quality. Unfortunately, after we checked and checked all the vaccum sources, wiring, adjusting TPS (q45 throttle body) We still cannot get it to idle correctly. We found that..
the blow off valve is pushing air constantly, pulled the vaccum hose (which runs to a dedicated bung on the manifold) and plugged it...to no avail

it idles high..about 1600 rpms...we tried adjusting the tension on the throttle cable...nothing. when we blip the throttle it revs up and drops, then rises, and drops...continuously.

We sprayed carb cleaner around the ports and throttle body to check for leaks, none present (the IACV and throttle body were put on with red RTV.)

The setup on the car is as follows:
Blacktop SR
2871R
740cc injectors
Enthalpy tune
z32 maf
SAFC as well
...etc

Any suggestions?

*slothonaleash* · 06-06-2009, 08:39 PM

adjust the spring on your blowoff valve? or get a new one

also try adjust your IACV if you haven't already done that, it may not be letting enough air through at idle

hayai_240 · 06-07-2009, 01:31 AM

I had a similar issue when I had to replace a gasket on my intake manifold. It turned out that the 2 hoses that ran to the IACV got kinked after I reinstalled it and caused my car to idle at 1500 constantly. After I fixed the kinks, my idle went back to normal. Just double check that the hoses aren't kinked.

SoguRacing · 06-07-2009, 01:37 AM

or you can try to get a tune done. a bigger throttle body will let more air by the throttle plate than calibrated compared to the stock unit.

*niSm095* · 06-07-2009, 07:01 AM

Today I'll check the hoses. try adjusting the idle screw and bov. If this doesn't work we were going to try to richen it up some with the afc. Thanks guys.

If anyone else has suggestions, please chime in.

*niSm095* · 06-07-2009, 06:10 PM

so...today...adjusted the BOV. Having a problem with it opening now, should the vacuum source be on the throttle body? or the manifold itself? I'm thinking its not getting enough vacuum to draw it open.

The IACV hoses weren't crimped, but we did adjust it.

With the combination of that, retarding the timing a little and messing with the three throttle adjustments on the q45 tb, we got it to idle pretty civily. I'm guessing since the addition of the manifold and huge throttle body I'm not going to be able to get as smooth an idle as I was before, is that correct?

06-06-2009, 08:20 PM	#1
niSm095 everything was beautiful... Join Date: Mar 2003 Location: SC Age: 24 Posts: 705 Trader Rating: (1)	installed intake manifold, car now idles poorly Today I swapped out the stock SR intake manifold for a custom made aluminum piece...very good quality. Unfortunately, after we checked and checked all the vaccum sources, wiring, adjusting TPS (q45 throttle body) We still cannot get it to idle correctly. We found that.. the blow off valve is pushing air constantly, pulled the vaccum hose (which runs to a dedicated bung on the manifold) and plugged it...to no avail it idles high..about 1600 rpms...we tried adjusting the tension on the throttle cable...nothing. when we blip the throttle it revs up and drops, then rises, and drops...continuously. We sprayed carb cleaner around the ports and throttle body to check for leaks, none present (the IACV and throttle body were put on with red RTV.) The setup on the car is as follows: Blacktop SR 2871R 740cc injectors Enthalpy tune z32 maf SAFC as well ...etc Any suggestions?

06-07-2009, 01:37 AM	#4
SoguRacing Post Whore! Join Date: Nov 2007 Location: (714) Age: 24 Posts: 2,948 Trader Rating: (23) Rides Gallery: SoguRacing	or you can try to get a tune done. a bigger throttle body will let more air by the throttle plate than calibrated compared to the stock unit. __________________ Pre Tune Checkup! Compression,LeakDown,Vacuum Test $80. Cams Install: $180

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06-06-2009, 08:39 PM	#2
slothonaleash Premium Member Join Date: Jan 2007 Location: Columbus, Ohio Age: 18 Posts: 640 Trader Rating: (4)	adjust the spring on your blowoff valve? or get a new one also try adjust your IACV if you haven't already done that, it may not be letting enough air through at idle

06-07-2009, 01:31 AM	#3
hayai_240 Leaky Injector Join Date: Jul 2006 Location: Seattle Posts: 140 Trader Rating: (2)	I had a similar issue when I had to replace a gasket on my intake manifold. It turned out that the 2 hoses that ran to the IACV got kinked after I reinstalled it and caused my car to idle at 1500 constantly. After I fixed the kinks, my idle went back to normal. Just double check that the hoses aren't kinked.

06-07-2009, 07:01 AM	#5
niSm095 everything was beautiful... Join Date: Mar 2003 Location: SC Age: 24 Posts: 705 Trader Rating: (1)	Today I'll check the hoses. try adjusting the idle screw and bov. If this doesn't work we were going to try to richen it up some with the afc. Thanks guys. If anyone else has suggestions, please chime in.

06-07-2009, 06:10 PM	#6
niSm095 everything was beautiful... Join Date: Mar 2003 Location: SC Age: 24 Posts: 705 Trader Rating: (1)	so...today...adjusted the BOV. Having a problem with it opening now, should the vacuum source be on the throttle body? or the manifold itself? I'm thinking its not getting enough vacuum to draw it open. The IACV hoses weren't crimped, but we did adjust it. With the combination of that, retarding the timing a little and messing with the three throttle adjustments on the q45 tb, we got it to idle pretty civily. I'm guessing since the addition of the manifold and huge throttle body I'm not going to be able to get as smooth an idle as I was before, is that correct?

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