HOW TO: Bad idle troubleshooting

mpg9999 · 03-06-2003, 10:37 PM

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

CleanSE-R · 08-26-2004, 09:50 PM

If you can, check your MAF sensor. These things can go bad in some rare cases. My car only has 63K miles on it. My SE-R was stalling and bucking, also lost some power. Took the MAF out of my '93 NX2K put it in my SE-R and the car ran fine. Bought a rebuilt MAF ($110 with 1 year warr.

) car now runs PERFECT!!

idriveanegg · 11-03-2004, 07:55 PM

what do i do if i turn the key, the engine turns over and starts, runs for about one second then slows and shuts off? no idle at all.

ScorchN200sx · 01-24-2005, 02:38 PM

I have the same prob starts and slowly shuts down? Alternator?????

hpro123 · 01-27-2005, 05:14 AM

Not enough fuel. Fill up your tanks. IF problem persists, check fuel pressure and fuel pump.

Chris

Dirk · 01-28-2005, 12:59 PM

feul pressure is oke i have a fpr tryed it on 3/3.5/4 bar and nothing changed

redclassic · 02-11-2005, 01:09 AM

last time it happend to me I held the key in place and the engine would stay idle, let it go then it would die, replace ignition. Maybe this might help.

KnightBird · 04-02-2005, 11:49 AM

Guys,.. if it doenst idle and slows and shuts down.. it MAY be your Intake Air Temp Sensor. Are you getting a SES or CEL? Mine didnt show up for 5 days after i started having the problem. I had this problem on my 2000 SE 2.0 and i had to take it to the dealrer to get it diagnosed.

FYI, My IAT Sensor just hangs in the stock airbox, because my CAI is installed as a Short Ram right now. It may have gotten wet and shorted out.

niSssEanR · 04-04-2005, 01:07 AM

How can you check for a miss? My idle is all over the place in my 92 sentra se-r. Also when i make a u turn to the left with the cluth in it will die on me. Can i get some help with both of these

kaim · 04-26-2005, 09:03 PM

Quote:

Originally Posted by niSssEanR

How can you check for a miss? My idle is all over the place in my 92 sentra se-r. Also when i make a u turn to the left with the cluth in it will die on me. Can i get some help with both of these

its the same with my 92' se-r but my car also dies when im parking or just slowing down at a stop sign. I just have to start it back up. If you find out the problem let me know what it is.

mickeyj36 · 04-28-2005, 12:55 AM

yea i got a weird situation...i just installed a gti-r into my 94 b13. i had to jump start it for it to start...now i found out that i was a dumba** and one of the plugs on the alternator wasn't in all the way. so i fixed that and voala, it started. however it backfired like hell and wasn't revving smoothly..and it would also occasionally die...now when this all happened i was running on a stock fuel pump....so i installed the walbro 255 today...and tried starting it up but it wouldn't start up this time...so i jumped it again and it started and idled perfectly and didn't get any backfire.....i turned off the car after 2-4 minutes of it running...then i tried to turn it back on and it would start running for maybe a second and then die....i tried pressing down on the gas pedal while starting it up and it would start up and as soon as i push that pedal it'll die....if i could get any help that'll be koo...thanks

walrusx4 · 04-28-2005, 01:32 PM

This might help some people.

one of my boots going into my distributor cap was too far up on the connection in there, so it was barely touching, causing some issues there. make sure the metal connector in your wire is touching the connection on the cap appropriately and entirely. This caused me to miss at idle. Now it's better.

good luck!

SoloSol · 06-01-2005, 10:32 PM

edit for being stupid

Peter · 06-03-2005, 10:53 AM

Quote:

Originally Posted by kaim

its the same with my 92' se-r but my car also dies when im parking or just slowing down at a stop sign. I just have to start it back up. If you find out the problem let me know what it is.

Coolant temperature sensor. Not the single wire one that
feeds the dummy light, the other one. $20 at Autozone and
a PITA to install.

Peter

Peter · 06-04-2005, 08:19 AM

Quote:

Originally Posted by Peter

Coolant temperature sensor. Not the single wire one that
feeds the dummy light, the other one. $20 at Autozone and
a PITA to install.

Peter

Somebody PM'd me about this, so I figured it would
be a good idea to share it with the thread.

There are two coolant temperature sensors.

One of them powers the stock gauge - which is about
as useful as the oil dummy light (not at all ...).

That one doesn't do jack to how your car runs.

The other one is what your ECU uses to figure out
the operating temperature, which has a lot to do
with how your car runs.

Wells p/n: SU405 available at Autozone for $17.99.

I don't know the Nissan p/n, but it's about the same price.

It's down under the air/idle assembly on the intake manifold
next to the passenger strut tower, near the oil filter.

The other one, which won't actually help the accuracy of
your gauge, but you may decide to replace while you're
there for the hell of it, is:

Wells p/n: TU84, for $8.99 at Autozone.

Credit goes to Ray Kawski for giving me the head's up on
that one a while back on the NE SE-R list.

Peter

92SE-R · 06-05-2005, 01:12 AM

My issue is that I have a Techtom. My water temp readings seem normal with this motor when compared to my last motor. My last motor idled awesome. This one sucks ass. So doesn't this mean my temp sensor is fine?

Peter · 06-05-2005, 07:42 AM

Quote:

Originally Posted by 92SE-R

My issue is that I have a Techtom. My water temp readings seem normal with this motor when compared to my last motor. My last motor idled awesome. This one sucks ass. So doesn't this mean my temp sensor is fine?

Then you have far more information than I.

I would check the standard culprits then, clean the valve
next to those sensors, check the TPS voltage, plugs, cap,
rotor, gap, idle speed.

For the TPS, .45 is the leaner side, .55 is richer.

Peter

sergofast · 01-04-2006, 06:45 PM

My car will idle at 1800rpm when its cold and sometimes doesnt drop ever. when it does it will go down to 1300 and then slowly- real slow- drop down to 1000 and then 750-800.

i replaced the O2 and temp sensor for the ecu last year and replaced the idle control valve with a used one from another forum member just a month or two after. and that fixed it for awhile (i couldnt get it to idle under 1100-1200). my fuel preasure is fine and the "power balance check" was fine. the car has 180 compression in all 4 cylinders.

i adjusted the icv last night and got it to work...for about 20 minutes and then it started acting up again. What do you check when you look for a clog? and what is the IAA and AAC valve harness?

thanks for the help,
Paul

Trace · 02-22-2006, 03:13 PM

Just wanted to throw something else out that can cause rough idle. After replacing a bunch of parts I took it to a local friend /mechanic and turned out it was a damaged crankshift position sensor. Probably happened when I hit some sort of critter. More than likely the one that broke the stillen urethane. So if you have hit anything recently maybe check it. I had idle that would bounce from 5 up to 1200 then back down.