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I noticed a decent amount of people here have idle problems, so I have typed up the FSM trouble diagnostics for an unstable idle. Enjoy:

1. Check EGR control valve for sticking (stick your hand under it and see if its stuck).
2. Perform power balance test: When disconnecting each injector harness connector one at a time, is there any cylinder which does not produce a momentary engine speed drop? If not, go to step 6.
3. Check Injector: Remove distributor from engine (crank angle sensor harness connector should remain connected). Disconnect ignition wires. Turn ignition switch ON. (Do not start engine). When rotating distributor shaft slowly by hand, does each injector make a n operating sound?
4. Check Ignition spark: Disconnect ignition wire from spark plug. Connect a known good spark plug to the ignition wire. Place end of spark plug against a suitable ground and crank engine. Check for spark. If no spark, check your coil, power transistor, and their circuits.
5. Check Spark plugs: Remove the spark plugs and check for fouling, etc.
6. Check Fuel pressure: Release fuel pressure to zero (pull fuel pump fuse and let engine die). Install fuel pressure gauge and check fuel pressure (at idle, it should be about 36 psi).
7. Check O2 sensor: Set “Exhaust gas sensor monitor” in the self diagnostic mode II. Maintaining engine at 2,000 rpms under no load, check to make sure that the red led on the ECU or the check engine light goes on and off more tan 5 times during 10 seconds.
8. Check for Intake air leak: When pinching blow-by hose, does the engine speed rise? If so, search for a leak.
9. Check idle adj. Screw for clogging: Disconnect TPS harness. Can you set engine rpm at 750 plus or minus 50 rpms by turning the screw? If not, check for a clog.
10. Do a compression check.

One thing this left out is checking the IAA. I would defiantly try that too if you are having idle issues. To check it, disconnect the AAC valve harness. If your engine speed does not drop, you may have a problem with your AAC valve.

I hope this helps you guys.

-Mike
 

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My Ass, your face
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Good job, Mike. That covers a lot of ground. I don't have the problem myself, but I'm sure somewhere down the line when I want to spend money or time on something else, it'll happen.

Now, I just need to get a fuel pressure checker thingy and a compression checker thingy, and a ....

Smart advice... later,
Mark
 

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Thats a nice write up.

But, before you start doing those checks:

1. Base Idle needs to be checked. See FSM.
2. Timing needs to be checked. See FSM.

If these 2 items are with in, or you can not adjust to spec- then look elsewhere. Keep it simple and START with the basics.
My $.02
 

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Yep i did all of those things, and passed, but im still running richer than you could ever believe and a horrible idle, did the diagnostic test and got a 5,5 back, i have no idea what would control how much fuel it should be taking that wouldnt be on the ecu
 

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Drive it like ya stole it
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NismoMan2 said:
I think ive found my sloution, would of never came up in the codes or anything, the fuel pressure regulator, i undid the return line on hte bottom of the FPR, not a drop coming out of it.
Holeyshit....that probably was forcefeeding the injecotrs lots of gas...:eek: :eek:
 

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Get Some!!
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What about MAF reground? Should I check that, too? I'm having the idle problem badly and I've been through these...

Thanks in advance,
 

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Drive it like ya stole it
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Jason92Classic said:
What about MAF reground? Should I check that, too? I'm having the idle problem badly and I've been through these...

Thanks in advance,
Yes, you should check that. Here is a few links on how to do it:
Due to the slowness of my internet service I can not provide you a link to the one on www.SE-R.net but you can go there and do a search for "maf reground" and find it.
Heres the acctual TSB(technical service builitin) on it, you will find a link on this page to pictures of it from Nissan:
http://www.se-r-list.org/selected.tsbs.phtml
Hope this helps.
~Ryan
Heres the link on SE-R.net:
http://www.se-r.net/engine/maf_ground.html
I decided to stop downloading at the same time I was browsing
:D
 

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mpg9999 said:
Those hose coming out of the PCV valve.
Im not sure I would pinch the hose coming out of the PCV valve and into the intake manifold, from my expeirence, those hoses are very brittle, and do crack.what about simply taking it off and putting your finger over it? Also, one thing all you guys might want to chime in here with is if your valve cover gaskets are leaking. If they are, then this would suck in UN METERED AIR. Think about it, leaky valve cover means there is a gap. The PCV system works on vacume, sucks air through the PCV valve, and then the hose on the other side of the valve cover goes back to the intake tube. This means it effectivly circulates air from AFTER the MAF to the intake manifold. Just some food for thought.
~Ryan
 

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The pcv vavle is on the left side of the valve cover with a hose coming off of it leading to the intake manifold. You need a wrench to take this off not sure what size prolly like a 12 mm maybe.
 

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my '92 intermitently lopes at red lights in traffic whether the a/c is on or not... it usually idles at about 900-800rpm but will sometimes dip to almost 400rpm where it feels like it will die... however, i leave it idling at the spray-n-wash for about five minutes and nothing seems to happen.. i guess i'm just worried about the engine dying in traffic... it already has new plugs, fuel filter, muffler, throttle cable etc... is it just characteristic?
 

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My NX idled like a b*tch for months. I went through most of the things already mentioned...no luck. Then, while it was at Rosen's in Richmond getting UR pulleys installed, another SE-R came in with the same idle problem. The solution for both of our cars? Simple...Engine Elec (B) fuse in the fusebox in the dash! Replaced the fuse, and she's idled fine since.

Maybe this will help...maybe not...but certainly worth checking. Cheap and easy!

Good Luck!

BTW, this fuse circuit has, among other things, the O2 sensor, something the engine/ECU definitely wants input from.
 

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if your pcv valve is that brittle that it cracks when u bend it, it is in DIRE need of replacement!!!:D
also, "The PCV system works on vacume, sucks air through the PCV valve, and then the hose on the other side of the valve cover goes back to the intake tube. " where u getting your vacuum from? heheh...........there is a tube that goes to the intake manifold, after the tb, where there is vacuum!! there is practically no vacuum in the intake hose, and what little there is is at wot, created by your filters restriction! ;)
peace
 

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saygmo said:
if your pcv valve is that brittle that it cracks when u bend it, it is in DIRE need of replacement!!!:D
also, "The PCV system works on vacume, sucks air through the PCV valve, and then the hose on the other side of the valve cover goes back to the intake tube. " where u getting your vacuum from? heheh...........there is a tube that goes to the intake manifold, after the tb, where there is vacuum!! there is practically no vacuum in the intake hose, and what little there is is at wot, created by your filters restriction! ;)
peace
All the PCV hoses between the valve cover and the intake manifold I have seen have been brittle, I think its the type of material they used to make that hose.

The VACUUM comes from the intake manifold, goes thorugh that hose to the PCV valve, sucks air FROM THE "T" on the other side of the valve cover and from the intake hose; so in essence circulates metered air through the engine(reburning all that crap in the crank case to be used in the combustion process). Unless of course you have a leak in the valve cover, then the PCV system can not possibly work correctly.
~Ryan
 
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