***THE FINAL IDLE THREAD***

[venom369]

Ok, here we go

So I, along with which seems like more than half of you, have been trying to diagnose/dial in my engine to obtain and maintain a perfect idle.

*CALLING ALL TECHNICAL EXPERTS* !!!

I will give you a scenario. Please take a quick minute to think about it and give your best solution:

- You own a Red S13 hatch equipped with an SR20det, FMIC, 225 walbro,...AND Actress/Model Megan fox is always chilling in the passenger seat for your pleasure. =]

Aight, sound good so far?, Hellll yeahhhh it does! =]

WELL one day you go to start your ride and like always Megan pops up once you insert the key, BUT when the engine starts the idle is horrible and even Megan opens the door, steps out and walks away for good.

Now whos pissed?! I know I am!!

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**NOW THE REAL QUESTION: What are the steps to make the proper adjustments to the engine to have AND maintain a perfect idle.

For example, for the sake of argument,

say my tps was at .30
say my iacv screw was all the way down
say my timing was at 20+

What would the steps be to adjust these different areas, IN ORDER!

-Timing first then mess with the idle OR idle first then adjust the timing?

***After I put the engine into "idle adjust mode", by warming the engine,revving it to 2k twice, killing it, unplugging the TPS, starting it, revving it twice again, what should I go to first to adjust the idle, the IACV or the throttle stop screw? Should I adjust the timing first?

WHAT ADJUSTS WHAT?
CAUSE AND EFFECT OF THE TPS/IACV/THROTTLE STOP SCREW/TIMING!


Should I adjust the tps first THEN mess with the iacv?


I notice the engine has 2 idle speeds, What exactly is this?
For example, Say I rev to 4k, the engine will decelerate normal to around 900rpm and stay there like it should BUT after like 15-20+ seconds it THEN falls to like 500-600 rpm and stays there untill revved again. WTF?
WHAT ADJUSTS THAT "second stage idle"? its so confusing.

Also my timing should be 15degrees at idle?, when the engine is revving it increases to around 20 BUT IT DOES STAY at 15 when idling. So whats the deal with this? Is this normal?

PLEASE HELP, NOT ONLY ME, BUT ALL WHO ARE SUFFERING FROM THIS ENTIRE IDLE ISSUE FOR GOOD.

The more info supplied there the better off ALL sr20 owners will be in the future, including myself

- Mike

[compactfean]

First thing is first. Before trying to tackle idle there cant be any vacuum/boost leaks. To do a boost leak test if you do not have a tester let me know and ill post my $15 harbor freight setup. You must check all couplers,clamps,intercooler, throttle body, intake mani, pcv and brake booster check valve, and all vacuum lines. Also if running open bov with the maf on the intake, do not continue to the next step. Recurc your bov or run blow through. Also make sure you have 4-6 inches of straight tube before and after maf if possible.

[venom369]

Sure man, post that boost leak setup.

But aside from that, I checked all vacuum lines, there good.
Tightened all clamp around every vacuum line and the fmic. Throttle body bolts are tight. I am running an open bov, BUT this problem happens if I rev to 1k or just let it idle on start up, so recirculated or not won't make a difference. Maybe under wot it will but thats a different thread.

-My maf is clean, tested the volts, everything checks out.(ground is perfect)
-The tps is set at .51 v oh..
**With the throttle adjustment screw all the way out and the tps pulled all the way down the highest the volts will go is .40 - .41 , so in order to achieve a higher voltage I have to turn the throttle stop screw in a little (which its supposed to be, right?)


The engine runs perfect when driving and at wot. no spikes no nothing, boost holds 100% steady.

I'm just trying to achieve a "secondary idle" around 900 rpm.
When the rpms are decelerating after a rev they will go down to around 800, sometimes bounce up to 1000 or 1500 depending on how much I messed with the iacv screw and then after 15 sceonds or so it will drop to like 500 rpm.

Whats the cause or what adjusts the "secondary idle mode" (real name- unknown to me) =]

[venom369]

my TPS has a max volts of .4 volts (with the throttle stop screw all the way out) and the tps pulled as far down as its able to.

Question: How far should my throttle stop screw be turned in,

OR

if anyone can do me a favor and check the max volts there tps CAN reach without messing with the throttle stop screw!, that would be awesome.

[compactfean]

The throttle stop screw is only meant to prevent the butterfly from sticking closed. Technically you don't even need it. You need to look at the butterfly and start screwing in the stop screw until it barely moves the butterfly....that's it. The best way to adjust the tps is with a scan tool our consult cable. The reason being is that even though the fsm says the tps can be between .3 and .5 closed, sometimes the ecu will still say the throttle is open even though voltage is within spec (lets say .48 v). This causes the ecu to not be able to go into idle mode. You may have to adjust the voltage lower. ONCE THE STOP SCREW AND TPS HAVE BEEN ADJUSTED CORRECTLY YOU ARE DONE. do not mess with this area as at this point it is set correctly. Next you need to adjust adle.
Step 1- start the car and get up to full opperating temp
Step 2- after car is warmed up, shut car off and disconnect tps.
Step 3- start car and rev to 2500 rpm 3-4 times to "lock in" the ecu to adjustment mode.
Step 4- confirm ecu is in adjustment mode, use timing light and see if timing is moving at all, if it hasn't than you are set to adjust idle.
Step5- adjust idle, turn idle screw ON IACV NOT THROTTLE BODY, clockwise or counterclockeise as needed. Idle should be stable between 750-850.
Step6- now that you've gone this far to adjust idle, it is the same exact procedure to adjust timing and you might as well do this now. With your timing light, make sure you are at 15° btdc. If not than loosen cas and adjust base timing,tighten and double check. If this changes your idle than adjust idle again and double check timing.
Step7- shut car off, connect tps, restart, and confirm settings are good.

[compactfean]

Another very important thing to check is if you have power to the iacv with ignition on. Ive seen alot of the wiring not done correctly. Its the small blue/yellow striped wire in the section of harness that is by the battery and fuse box.

[compactfean]

Just watched your vid....seems like a bad sensor, rather maf or knock, cts, something like that. Your idle shouldnt be that choppy. And wouldnt be from an iacv adjustment.

[venom369]

Yo man you are the best! Hands down the best info in any thread ever about the complete idle/timing procedure.

I checked the ecu and the knock sensor (#34) code appeared. So I will be replacing that asap(checking the wiring before hand ofcourse)
ALSO, the engine temp wont stabilize in the middle of H and C, its always only like 2 notches above C. Idk if its due to the fmic but.... ya know what? f*** it. im just replacing the cts AND the knock sensor lol. and ill save the maf for the last culprit.

Thanks again man, once again A+ info!

[compactfean]

no problem...let us know what fixes it for you. Save it to your desk top and pass it on....eventually you will have nemorized it like me after seting the idle and timing 100 times and researching and reading every fsm/ forum post to get my car to idle puurrrrfect with 740cc inj, z32 maf etc.

[venom369]

no problem...let us know what fixes it for you. Save it to your desk top and pass it on....eventually you will have nemorized it like me after seting the idle and timing 100 times and researching and reading every fsm/ forum post to get my car to idle puurrrrfect with 740cc inj, z32 maf etc.

Alright.... heres the update...

-Started with the throttle screw all the way out then slowly turned it in until the butterfly JUST started to move then stopped. THEN adjusted the tps to .45 volts

-Warmed the engine
-shut off,unplugged tps
-started engine, revved to 2500 3 times
-Got it into idle/timing mode (timing was locked)

However, when i set the timing to 15 degrees (second mark from the right) the engine will idle VERY low around 300 rpms and shake violently.

I unscrewed the iacv screw all the way and still would end up being at the same idle. I also checked if the iacv was getting power and it was, around 12 volts.
When I unplugged the clip the idle would change so the iacv is working.

THE FIX: Increasing my timing to 21. NOW when I start the car the engine revs instantly up to 800 rpms... and stays there. (as opposed to starting the engine and it only reving up to 400-500 rpms, then having to manually give it gas for a second or two to get it up to 800 rpms.

ALSO the idle doesn't drop now, it use to be at the right rpms (800) and shortly fall to the "s*** second stage low idle around 600 rpms"

The only code the ecu is throwing is for the knock sensor, which I am waiting for it to be delivered. I DOUBT that a faulty knock sensor can cause all of this, but... any way it could ?

Im about to throw in the cards and take it to a shop, cause this is driving me crazy. But I still have some fight in me =].

Any thoughts compactfean? or anyone else whos got some exp with idle/timing feel free!!

Once again thanks!

[compactfean]

Well with a knock sensor code the ecu is going into safe mode which yes....it will cause horible idle, usually very rich etc. the wierd thing is that usually the car will continue to run like crap until you turn the car off and restart it. Your car doesn't do that. Its almost like it exits safe mode when you rev it. Also I dont know if because its in safe mode turning the idle screw doesn't work, but before worrying about all that I'd tackle the knock sensor code first because it will definately cause more issues than you think....also the cts can put it safe mode if bad. What ever you do don't leave your timing at 21°, thats just asking for disaster.

[venom369]

I hear you man, Yes I deff have to fix those sensors first

The weird thing is when i'm in "timing lock mode" And I set the timing to 15 the engine idles as if its about to die, I adjusted the iacv screw and the throttle stop screw and neither things causes any change. so having the engine around 21 is the least it can be at and actually run.

Also maybe this is because my timing is so high(which i set it last night) But my boost doesnt fully kick in with the full force, It shows 9psi steady on the gauge but the car runs soo poor when boosting.

[compactfean]

The poor accel when boosting is definately from the knock sensor. You could try a resistor just to see if that's what it is before replacing the knock sensor. Im not sure what ohm you use though.

[venom369]

The poor accel when boosting is definately from the knock sensor. You could try a resistor just to see if that's what it is before replacing the knock sensor. Im not sure what ohm you use though.

Yessirr thats exactly what im in the process of doing! I think my knock sensor has been gradually getting worse over these last 3 months.

You think if the CTS was bad/faulty the ecu WILL ALWAYS throw a code for it? because the knock sensor is the only one on the ecu.

ALSO

FOR ANYONE READING THIS, you use a 1 mega ohm resister and attach (solder it) to one end of the knock sensor signal wire then ground the other end of the resister.


so its:[ECU] (pin #27)---->-->---[Signal wire]--->---->[ 1 mega ohm resister]-->---> [ground]

I will repost back with the results!

[compactfean]

If a cts is bad it doesnt always throw a code. I just went through this with my 200sx ser. It was idling like crap and smoking but never threw a check engine in. months. Replaced cts and problem solved. Excited to see what happens with the knock sensor issue.

[venom369]

OK, SO

I did the 1ohm trick and it worked. I checked the ecu only to find code #55 =]

Then, I repeated the timing/idle procedure stated above.

Results: ...Things are similar but slightly changed (maybe due to the knock sensor fix.)

Timing is now at 16 =]
When revved up the car acts as it should, and returns idle around 600 rpms and quickly raises to 800 rpms (YES!) and stays there for around 15 seconds,

BUT after around that 15 seconds mark the engine drops idle to around 200 rpms and shakes like hell as you can imagine. Vac is around -5

When rpms are this low (200 rpms) I hear an occasional ticking noise which sounds as if the coil wires are arching (this common?) ALSO I will hear one of those "ticks" RIGHT before the engine dies, everytime. im thinking new coils are soon? lol idk shoot your thoughts!

Here is a video I took 10 mins ago, the constant ticking noise throughout the video is the timing chain rattle i think. (The engine doesn't die in this video) However If I let it idle at 200 for a while it will

ALSO THAT NOISE AROUND :26+ is the maf bumping against the fuse box.

[youtube]http://www.youtube.com/watch?v=aYf9uY-TqvQ[/youtube]

[kingtal0n]

The tick could be related to the valvetrain. Ive had SR20's make a TICK noise from the head, then die, the valve spring was getting stuck down, leaving the valve open, causing compression loss and pushing air back into the intake... which would screw up the idle air quantity and kill the engine.


I am not saying this is your problem but consider that the valvetrain could be at fault. I would do a compression test and watch the valvetrain while cranking the engine for "sticking springs".

Next I would diagnose this as an electronics/air issue. boost leaks, maf sensor, ECU, tps, cas, coilpacks, etc... I would start swapping out parts with known good parts to find a part that makes the difference. Without spare parts you are stuck doing voltage checks with a multimeter and sometimes that does not tell all.

You might be able to narrow it down by using logic. For instance if the engine is idling roughly at 200rpm and seems like it wants to die, but you hit the throttle and it comes right back to life and revvs fine, and if the car drives fine, the problem probably is not the ECU or CAS or TPS for instance. The MAF might be good, but an air leak can cause a "bad maf" symptom, especially after the maf and before the turbocharger. The engine will run lean if there is an air leak there and gives this symptom. You might be able to spray some carb cleaner into the intake (on the air filter) during the rough 200rpm idle, if the idle picks right up then its probably sucking air after the maf and not getting enough fuel (maf reading low) -- That would cause a lean air-fuel while boosting which can blow the motor so beware.

[TheRealNap0le0n]

if your car only has -5 vacuum you have a vacuum leak bro

[compactfean]

^ we talking about bar or inch pounds? Inch pounds, yes ....huge problems. Bar...he is good.

[venom369]

^ we talking about bar or inch pounds? Inch pounds, yes ....huge problems. Bar...he is good.

It has -5 vac only when the idle drops to 200 rpms, otherwise, when idling around 800 the vac is like -19.

[venom369]

Alright, swapped out the old coolant temp sensor with a brand new one, let it warm up then test drove it.

When boosting the boost gauge does show up to 9psi like normal but the engine acts worse/sluggish when ANY boost is registering (engine never gets boost). ALSO when I rev in neutral the exhausts starts popping on deceleration, so Im running rich, hmmm

symptoms of a bad 02 sensor? Upper or lower?

[venom369]

And regarding vac leaks I checked all over with carb cleaner AND propane, even took off the rubber intake and checked for cracks, NONE. Then went further and wrapped the whole thing in a coat of electrical tape, changed nothing. Tightened all ends of the hot and cold pipes and the fmic. every clamp in the engine bay is tight! Put new vac lines running to and from the boost controller to the waste gate and the throttle body.

[venom369]

Regarding the ignition coils:

-Disconnected each one, one by one, engine idle changed. (good!)
Then unscrewed the screws and pulled each coil out of the socket about 2 inches up and they all made a ticking noise (also good right? that means its making spark? idk lol?

[venom369]

The tips of all 4 of my spark plugs are half white and half black, i assume this if from running lean/rich.

I will be replacing the plugs tomorrow with bkr6e's.
ALSO a new fuel filter will be installed as well.

Will post back and keep this thread updated!

[venom369]

This is the MAFS test, im leaning toward my problem being a bad/faulty/maf thats on its way out. (i already cleaned it like 4 times prior to this, i think its just shot)

let me knoww what u think

[youtube]http://www.youtube.com/watch?v=i_F2Rq89Ba8[/youtube]

[compactfean]

Yeah id say try a known good maf. Have you checked the voltage from maf at idle and 2500 rpm? The specs are almost the same as the ka so you can fallow the test procedure from the 240sx fsm

[venom369]

Got a new sr maf on its way, Im almost sure this is the problem .

I will post the results after its installed in the next day or so!

[venom369]

Alright, SO!

New maf installed, and the idle problem is 10000% fixed. The problem in the last video i posted is also 1000% fixed. Car idles PERFECT (FINALLY)

BUT, even since I messed with the timing it has had this "no power" problem

When I put the engine into timing lock mode, I can set it at 16 degrees no problem. I watched it for 5 minutes straight and it did not budge from 16. (second mark from the right.)

HOWEVER, when I shut the car, reconnect the tps, start the car and check the timing. Its another story, the timing is around the first mark (on the left!!) and it stays there. Even when I rev the engine the most the timing jumps to is around the middle of the white marks.

WHAT IS GOING ON HERE, BAD TPS?

The tps is adjustable just like its supposed to be. I have it set at .40 at the moment. (I know .45 is ideal)

Idk guys im lost on this one, share your thoughts!

[compactfean]

At this point I would get a consult cable so you can see what your engines doing....the thing that sucks about obd0 and obd1 "style" ecus is that lets say you have no codes and all sensors are within spec to not throw a code but there is still a problem. I just replaced my cts on my b14 because when I was monitoring all my specs the ecu saw that the engine was at 250 degrees....made it run rich and retard timing to try and cool the engine down....it was at perfect opperating temp. Because the ecu recieved some sorry of signal it didnt throw a code....that doesn't mean that that signal was correct.

[compactfean]

If you think about how the nissan ecu works... There are 4 major sensors that affect timing, tps,cts,maf, knock. All these play a role nissans way of giving a "tp" value and within that value gives fuel duty cycle and ign timing. There "theoretical pulsewidth" also includes a guess of how much load is on the engine and since timing doesn't move much, maybe thats a clue to what's going on. You have a wideband or anything to monitor what your engine is doing?