S13 SR20DET Blacktop High Idle Problem

[89TwoTone]

S13 SR20DET Blacktop Idling Problems

I have a Nistune daughterboard along with a consult port hooked up in order to diagnose and troubleshoot (not tuning yet) and that is what has given these values on this post. I don’t want to use Nistune as a band-aid, I’d rather fix the problem with the engine/sensors itself.

Problem: When the car is dead cold, the idle is around 900rpms and the timing is at 15 degrees as it should be at operating temp idle. As soon as the temperature hits 60 degrees, the timing advances itself to 36 degrees and the idle changes to about 1800 rpms. I have a timing light to read the tick marks on the crank pulley and it reads about 12 degrees, while Nistune shows 36 degrees. This to me shows that the ECU is reading different timing than the crank pulley marks.

Troubleshooting I’ve Completed: The TPS is at .5 volts with the throttle closed, so it doesn’t need adjustment, and neither does the throttle adjustment screw. TPS Voltage rises steadily and drops steadily as the throttle is opened and closed. I pulled the CAS out, took off the valve cover, and reset the cams to top dead center. I then placed the CAS back at TDC as well (To me, if this was done wrong it wouldn’t read 15 degrees while cold). TDC was set according to this link: http://www.frsport.com/How-To-Set-Crank ... _t_25.html The IACV is screwed all the way in, and does not effect the idle as it is adjusted. My IC piping is all welded, so I know there is not a leak within that. I have checked all my vacuum lines and rechecked them, only to find no leaks. My AFR is mid 14-15 at operating temp.

Questions I have: Coming off the intake (Greddy suction kit) there is a hose connected to a T on the valve cover. One end goes into the cover, while the other goes to a black box, then comes out and goes to something else. Can this “black box” be deleted? Is it adding extra vacuum problems? Is Nistune automatically loading a different timing map once the engine hits operating temperature? I have bigger injectors, but have set the correct cc’s in Nistune and don’t know if this could have an effect. I have read and read different troubleshooting tips and posts and can’t find anything this specific. If you are just going to reply with “search google” I’ve done that already. If you find something specific enough and think it will help just post the link. I'm new to Nistune, but am not new to an SR. Any input will help.

Mods: Greddy suction kit, Garrett GT28R Spec R turbo, Z32MAF, Greddy intake manifold, HKS hotpipe with HKS SSQ BOV, Megan Racing exhaust manifold-dump pipe-downpipe-testpipe-exhaust. Mishimoto radiator-12in fans-innercooler, Walbro 255lph fuel pump, HKS 555cc (yellow top Nismo 608cc) injectors, Nismo Type A FPR, Z32 Fuel Filter, Garrett Boost Gauge, AEM Wideband UEGO AFR gauge, Nistune type 3 Daughterboard.

[89TwoTone]

Anyone have any ideas?

[OM3GA]

What does the Nistune think that the temp is? Maybe it is forcing the IACV or AACV to up the idle because it thinks the engine is cold.

Don't worry about the black box unit, it is just a standard catch can to drain oil back into the block if it gets out of the T fitting, you definitely want to keep it there. I have done plenty of research since i wanted to eliminate it before as well. The only REAL way to eliminate it is to do an S13.4 valve cover from Touge Factory.

OMG3000POSTS

[Jmoore124]

How long have you had the motor? Is this a new problem? It still sounds to me like an IACV issue or bypass issue.
You seem like your pretty competent. What I would do is find a fsm and go through and do the running test on the iacv. I know I had a similar problem out of a red top I had. It tells you to go through a bunch of different steps like unplugging it to see if idle goes down etc. You can probably find just the iacv article if you google it.

[89TwoTone]

What does the Nistune think that the temp is? Maybe it is forcing the IACV or AACV to up the idle because it thinks the engine is cold.

Don't worry about the black box unit, it is just a standard catch can to drain oil back into the block if it gets out of the T fitting, you definitely want to keep it there. I have done plenty of research since i wanted to eliminate it before as well. The only REAL way to eliminate it is to do an S13.4 valve cover from Touge Factory.

OMG3000POSTS

As soon as it hits 60 degrees (reading from Nistune) the idle goes up. It is almost as if it is doing an inverted process. When its cold, it idles at about 900 (where it should be at operating temp) then when it hits 60 degrees the idle rises. I have adjusted the IACV and it doesn't seem to do anything.

How long have you had the motor? Is this a new problem? It still sounds to me like an IACV issue or bypass issue.
You seem like your pretty competent. What I would do is find a fsm and go through and do the running test on the iacv. I know I had a similar problem out of a red top I had. It tells you to go through a bunch of different steps like unplugging it to see if idle goes down etc. You can probably find just the iacv article if you google it.

The motor has been in the car for a couple years now and has never ran right (crazy idle, bogs in boost, terrible throttle response) having a JWT bench tune. I started reserching Nistune and picked it up. Before I start tuning for actual performance I want to get it running right.

I've tried testing the IACV and adjusting it and get no results. I've read that the spring inside becomes weak and doesn't adjust, so I've been looking for a stock SR intake mani to pull it from since they run for about $50 bucks on ebay. An OEM one off FR-Sport is $400+ which is crazy to me. I haven't been able to work on the car since the original post, but I probably will this coming weekend. I appriciate the help and if you guys have any more suggestions let me know.

[Jmoore124]

Good luck to you. I hate chasing bugs like that. IACV is where I would start, then make absolutely sure you have no vacuum leaks (smoke test, plug etc) Is your CEL operational? Try using your obd2 port for diagnostics if your able.

[compactfean]

Obd2 doesn't exist on either a 89 240 or an sr20. What is available to him is the consult which he is already utilizing. When setting the timing it must be set by the fsm procedure. (reason being is that the ecu doesn't know if the engine is ACTUALLY at 15° so you have to fallow the timing procedure to TELL the ecu that it is at 15°) this can only be done when the engine is at full operating temperature and this is the reason that your ecu says your at 15° and then when warmed up, changes to 36°. There should also be a correction factor for timing somewhere in your base settings in the nistune software to fix ”actual” timing versus what the computer perceives but id mess with it some more and get it closer, that way your not ”correcting” 21° of timing when you shouldnt have too.

[compactfean]

the-final-idle-thread-t536493.html
Also check this out, this is the most detail I could remember for setting the timing/idle on our troublesome cars. Lol

[89TwoTone]

Obd2 doesn't exist on either a 89 240 or an sr20. What is available to him is the consult which he is already utilizing. When setting the timing it must be set by the fsm procedure. (reason being is that the ecu doesn't know if the engine is ACTUALLY at 15° so you have to fallow the timing procedure to TELL the ecu that it is at 15°) this can only be done when the engine is at full operating temperature and this is the reason that your ecu says your at 15° and then when warmed up, changes to 36°. There should also be a correction factor for timing somewhere in your base settings in the nistune software to fix ”actual” timing versus what the computer perceives but id mess with it some more and get it closer, that way your not ”correcting” 21° of timing when you shouldnt have too.

Thank you so much for the info and the link. This weekend I worked on getting the differential welded along with some suspension stuff; so, I will get back to this issue since I just got on tonight and saw this. I'll keep you guys updated with what works. Thanks again.