Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Go Back   Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum > General > Tech Talk > Engine Tech

Engine Tech Technical discussion related to all relevant engines such as KA, SR, RB, CA, 2JZ , L24/26/28, VG, VQ, and LSx series.


Reply
 
Thread Tools Display Modes
Old 04-03-2022, 08:13 PM   #1
gavs
 
Join Date: Nov 2019
Location: los angeles
Age: 22
Posts: 30
Trader Rating: (0)
gavs is making his/her stupidity well-knowngavs is making his/her stupidity well-knowngavs is making his/her stupidity well-knowngavs is making his/her stupidity well-knowngavs is making his/her stupidity well-known
Feedback Score: 0 reviews
SR S14 SR20 rough idle and throttle response issue.

i have a 1990 s13 coupe with a notchtop s14 sr full swap done. relevant mods include fmic, upgraded rad, hks non recirc bov, full exhaust. bought the car already swapped and the idle has been rough since day one of ownership. now it has seemingly developed a throttle response issue that comes and goes at random.

the idle will jump around between 600 and 1k rpm, never dies though. always maintains idle, but its just rough. the car only had issue maintaining idle once after i started it after stalling it on a hill.

for the throttle issue, i can be cruising along normally and when i give throttle, theres no response for about a second or two. doesnt happen at all times, but will occasionally pop up. happened on one drive frequently but has only happened a handful of times since then.

the car runs rich but not excessively. pulls strong and has no issues under boost or while drifting/driving hard. on stock boost of 7psi.

the previous owner didnt build the car either, but thankfully he knows the person who did so im still learning about the car from who originally did the swap. the previous owner pointed to the tps as a potential cause of the idle issue.

before i dive into anything, any second opinions or other ideas would be greatly appreciated.
gavs is offline   Reply With Quote
Sponsored Links
Old 04-03-2022, 08:27 PM   #2
Om1kron
Post Whore!
 
Om1kron's Avatar
 
Join Date: Sep 2004
Location: Granada Hills, CA
Age: 43
Posts: 6,990
Trader Rating: (15)
Om1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfection
Feedback Score: 15 reviews
what ecu? if stock did you check for codes, probably throwing a knock sensor code. if so you either need to replace it or you can put a resistor 1mhz 1ohm in the sub harness connector for the knock sensor to bypass it. I haven't run an knock sensor since I installed my motor.
__________________
Wayne Edwards
https://om1kron.blogspot.com
Om1kron is offline   Reply With Quote
Old 04-03-2022, 10:16 PM   #3
gavs
 
Join Date: Nov 2019
Location: los angeles
Age: 22
Posts: 30
Trader Rating: (0)
gavs is making his/her stupidity well-knowngavs is making his/her stupidity well-knowngavs is making his/her stupidity well-knowngavs is making his/her stupidity well-knowngavs is making his/her stupidity well-known
Feedback Score: 0 reviews
stock ecu. will definitely check for codes tomorrow.

bypassing the knock sensor may be a good idea.

any ideas on the idle issue? could just be minor vacuum leaks, will check for that as soon as i get the car to my families shop.

it hopefully isnt anything major, the car runs great besides the idle.
gavs is offline   Reply With Quote
Old 04-04-2022, 01:30 AM   #4
Om1kron
Post Whore!
 
Om1kron's Avatar
 
Join Date: Sep 2004
Location: Granada Hills, CA
Age: 43
Posts: 6,990
Trader Rating: (15)
Om1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfectionOm1kron is close to perfection
Feedback Score: 15 reviews
There's a whole ass procedure to set idle on an sr which I cannot recall. but yes check all your hoses.
__________________
Wayne Edwards
https://om1kron.blogspot.com
Om1kron is offline   Reply With Quote
Old 04-05-2022, 12:54 PM   #5
s13 @ fullboost
Post Whore!
 
s13 @ fullboost's Avatar
 
Join Date: Dec 2007
Location: St.Petersburg,FL
Posts: 2,548
Trader Rating: (15)
s13 @ fullboost is close to perfections13 @ fullboost is close to perfections13 @ fullboost is close to perfections13 @ fullboost is close to perfections13 @ fullboost is close to perfections13 @ fullboost is close to perfections13 @ fullboost is close to perfections13 @ fullboost is close to perfections13 @ fullboost is close to perfections13 @ fullboost is close to perfections13 @ fullboost is close to perfection
Feedback Score: 15 reviews
Send a message via AIM to s13 @ fullboost
You can play with the IACV adjustment located on the back of the intake, I believe counter clock wise will raise RPM & clock wise should lower.


Quote:
Originally Posted by Kingtal0n View Post
The diagnostic moral here is that airflow sets the idle speed, the system should be pressure tested, make sure it is air tight i.e. you should be able to shut an engine off by covering the throttle body and similar ports (with your hand for example if you cover the TB/IACV the engine should die, if it kept running you have a leak somewhere)

fuel and timing influence/adjust idle speed, while airflow always sets the idle speed

How to adjust the idle speed on a high performance engine for maximum compliancy (very unlikely to suffer bearing damage due to low idle speeds, which may occur on engines with older ECU or old technology IACV type valves)
1. Get the engine warm, set idle Air fuel ratio, use 15* btdc on sr20det engines with a MAF sensor for best results, allow idle wander up to 22* btdc
2. Load the engine with headlights and electric fans, and any other devices you intend to run in the car frequently.
3. disable the IACV somehow; plug airflow holes that lead through any automatic idle control valves so no computer idle speed adjustments can occur for the next step
4. Engine warm and loaded up, set your idle speed using IACV manual adjustment (or throttle body base adjustment if the engine in question has no IACV) 10-60rpm below desired Idle speed.

5. Plug back in (re-enable) the IACV (or computer control) so the computer can use the valve to add that 10-60rpm back into the idle speed to achieve desired idle speed. If the ecu is OEM this is around 850rpm on sr20det. otherwise, units like the PFC have adjustable desired idle speed. If my desired idle speed is 900rpm for example, then my base idle speed with no computer control would be around 860rpm so the computer only needs to add a little bit of air to reach 900. Keeping the two settings (base idle and desired idle) very close will help stabilize the idle of the engine, especially if it has a long duration camshaft.
__________________
s13 @ fullboost is online now   Reply With Quote
Old 04-05-2022, 02:21 PM   #6
kennn
Zilvia Member
 
Join Date: Mar 2011
Location: USA
Posts: 254
Trader Rating: (17)
kennn is an unknown quantity at this point
Feedback Score: 17 reviews
You need to set base timing first. The cheapest software I can find: https://nisscan.com/NDSI/index.php?c...=supportedcars

You can check codes, set base timing, and set idle speed

I would recirculate the bov to eliminate the variable. The spring could be set too weak and cause all kind of leaks
kennn is offline   Reply With Quote
Old 04-07-2022, 09:11 AM   #7
LoSt180
Zilvia FREAK!
 
LoSt180's Avatar
 
Join Date: May 2013
Location: MD
Posts: 1,049
Trader Rating: (18)
LoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond reputeLoSt180 has a reputation beyond repute
Feedback Score: 18 reviews
Check the ECU for codes using the consult port. NDSI is a good one, and there's a few others. While you're looking, it's pretty easy to monitor the TPS voltage from closed to wide open in order to determine if that is an issue.

Check for vacuum leaks and verify base timing has been set, since those are the major causes for idle hunting. I'd guess one of the vacuum ports off the intake/throttle body isn't capped off, or has a cracked rubber line.

Once you get that sorted out and since you have a S14 SR, those actually use a wastegate solenoid to bump the "stock" boost to around 11psi. The wiring is there, you just need something like a MAC valve and connect it so that it bleeds air from the vacuum line going to the wastegate. Then really enjoy the full value of a stock-ish S14 engine, because running off base wastegate pressure sucks, feels so sluggish in comparison.
LoSt180 is offline   Reply With Quote
Old 04-11-2022, 07:32 PM   #8
jr_ss
Post Whore!
 
Join Date: Dec 2005
Location: Pa
Posts: 6,410
Trader Rating: (35)
jr_ss has a reputation beyond reputejr_ss has a reputation beyond reputejr_ss has a reputation beyond reputejr_ss has a reputation beyond reputejr_ss has a reputation beyond reputejr_ss has a reputation beyond reputejr_ss has a reputation beyond reputejr_ss has a reputation beyond reputejr_ss has a reputation beyond reputejr_ss has a reputation beyond reputejr_ss has a reputation beyond repute
Feedback Score: 35 reviews
Send a message via AIM to jr_ss
Dead spot in the TPS sweep. Check TPS voltages.
__________________
*My SR20VET* Does your VTC gear rattle in your S14/15 SR? PM me.
jr_ss is offline   Reply With Quote
Old 07-10-2022, 12:54 PM   #9
RaidenKing
Zilvia Member
 
Join Date: Sep 2005
Location: Jacksonville, FL
Age: 35
Posts: 169
Trader Rating: (0)
RaidenKing is on a distinguished road
Feedback Score: 0 reviews
Did you ever solve the idle issue?

I agree with what others have said, but I did all that before finally realizing the issue was my alternator. Replaced it with a P2M alternator and it idles fine now.

Granted, mine was stumbling and dying half the time. I should have known right away when turning on stereo, AC and lights would cause it to stumble further.
RaidenKing is offline   Reply With Quote
Reply

Bookmarks

Tags
240sx, idleissue, s13, sr20, sr20swap


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -6. The time now is 01:34 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2024, vBulletin Solutions Inc.
vB.Sponsors
Copyright ? 1998 - 2022, Zilvia.net