HELPP - Rough Idle!! - Nissan Forum
GA16DE 1.6L Engine Engine Discussion: 91-99 Sentra, 95-98 200SX, 91-93 NX1600

 
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post #1 of 15 Old Oct 28th, 2011, 01:46 AM Thread Starter
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HELPP - Rough Idle!!

so today i decided to clean my throttle body. i took off the intake and all the hoses connecting to the throttle body... took the throttle body off... sprayed it down with carb cleaner... and put it back... heres the thing though... i didnt get a new gasket and a piece of the old gasket came off... so now its missing a piece of gasket. also i didnt take the tps and iacv sensor off of the throttle body while cleaning it.

i personally think its the gasket but im just wondering if it could be the sensors too... thanks

1995 200sx
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post #2 of 15 Old Oct 28th, 2011, 03:09 AM
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You don't need to disconnect anything to clean the throttle body. All you need to do is turn the throttle drum to open up the throttle plate and spray down the inside of the throttle body and the throttle plate with some throttle body cleaner or carb cleaner. Since you already know the gasket was torn, I'd start by replacing the gasket and go from there. I'd also leave the IACV-AAC valve and TPS on the throttle body.
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post #3 of 15 Old Oct 28th, 2011, 10:40 AM Thread Starter
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thanks man... im gonna get a new gasket tomorrow and put it on there... i hope all goes well. also lets say it doesnt work... what else might it be?

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post #4 of 15 Old Oct 28th, 2011, 10:42 AM Thread Starter
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Oh and also when i start up my car the rpm is really high maybe around 1500 then it goes down and down and down to like 500 then the engine really starts to shake hard and then it evenntually stalls on its own

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post #5 of 15 Old Oct 28th, 2011, 01:57 PM
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The IACV-AAC valve controls the fast idle and maintains base idle by compensating for loads placed on the engine, ie P/S, A/C, etc. It is commanded by the ECM. For it to work properly, base idle setting must be correct. This is usually done by warming up the engine to normal operating temperature (run engine at 2000RPM for 2 mins) and shutting it off. Unplug the TPS and restart. The IACV-AAC valve and TPS are now in a "fixed" position and the idle speed is now the base idle. Adjust the screw on the IACV-AACV until the engine will idle (if necessary...lower, if too high) and adjust the ignition timing to spec (rev the engine 2000-3000RPM a few times with all loads and accessories off before doing this). Timing spec is 8 degrees BTDC +/- 2 degrees. Adjust the idle.
AT: 725 +/-50 RPM
MT: 625 +/-50 RPM

Turn off engine and reconnect TPS.

If you still have idle problems and you've done your basic checks (confirmed no vacuum leaks, ignition system OK, etc.), you could have a faulty IACV-AAC valve and/or a bad diode. Refer Nissan technical service bulletin NTB97-008.
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post #6 of 15 Old Oct 28th, 2011, 10:47 PM Thread Starter
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wow... awesome thanks man... im gonna try all that... but im pretty sure my ignition system is perfect because it was running perfectly fine before i cleaned the throttle body but it woudlnt hurt to check it anyway... thanks man

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post #7 of 15 Old Oct 28th, 2011, 11:02 PM
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Quote:
Originally Posted by smj999smj View Post
The IACV-AAC valve controls the fast idle and maintains base idle by compensating for loads placed on the engine, ie P/S, A/C, etc. It is commanded by the ECM. For it to work properly, base idle setting must be correct. This is usually done by warming up the engine to normal operating temperature (run engine at 2000RPM for 2 mins) and shutting it off. Unplug the TPS and restart. The IACV-AAC valve and TPS are now in a "fixed" position and the idle speed is now the base idle. Adjust the screw on the IACV-AACV until the engine will idle (if necessary...lower, if too high) and adjust the ignition timing to spec (rev the engine 2000-3000RPM a few times with all loads and accessories off before doing this). Timing spec is 8 degrees BTDC +/- 2 degrees. Adjust the idle.
AT: 725 +/-50 RPM
MT: 625 +/-50 RPM

Turn off engine and reconnect TPS.

If you still have idle problems and you've done your basic checks (confirmed no vacuum leaks, ignition system OK, etc.), you could have a faulty IACV-AAC valve and/or a bad diode. Refer Nissan technical service bulletin NTB97-008.


You must be a Paper Mechanic or Something.

Last edited by nissanthrowback; Oct 28th, 2011 at 11:05 PM.
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post #8 of 15 Old Oct 28th, 2011, 11:18 PM
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Quote:
Originally Posted by nissanthrowback View Post
You must be a Paper Mechanic or Something.
Well clever man, how about you (as a REAL mechanic) try and describe in words how to set timing and idle properly to a non-informed person then?
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post #9 of 15 Old Oct 28th, 2011, 11:21 PM Thread Starter
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well i dont need to know how to set my idle... i know how to set the idle and timing and what not... my problem here is that my car idles rough and i want to know if its either one of two reasons.. i have half of a gasket on there so theres only half of a gasket on the throttle body. then i wanted to know if my tps and iac could be damaged from spraying carb cleaner on it. but im pretty sure its the gasket

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post #10 of 15 Old Oct 28th, 2011, 11:25 PM
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Half of a gasket present iso a complete one means a vacuum leak - sort that to start with since you know the thing was ok before you started. TPS and IACV is totally fine with carb cleaner.

FWIW - cleaning the TPS and IACV will most likely require resetting the idle speed since you effectively change the flow characteristics/volume of the IACV.

Last edited by LvR.; Oct 28th, 2011 at 11:28 PM.
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post #11 of 15 Old Oct 28th, 2011, 11:27 PM Thread Starter
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Thanks for the solid advice bro... i appreciate it

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post #12 of 15 Old Oct 29th, 2011, 06:33 AM
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Quote:
Originally Posted by nissanthrowback View Post
You must be a Paper Mechanic or Something.
Actually, I'm a former certified Nissan Master Technician. I started with them as a detailer/mechanic's apprentice in 1985 when I lived in my home state of NJ and worked my way up the ladder. I left both Nissan and NJ in Oct. 2003 and moved to Virginia where I now work for the VA Dept. of Corrections. If you have any other questions or comments, I'm not hard to find! One more thing: you should never assume! Like the old saying goes, "You should never ASSUME, because when you ASSUME, you make an ASS out of U and...well, in your case, just "U."
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post #13 of 15 Old Oct 30th, 2011, 07:15 PM Thread Starter
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i put a new gasket and now it runs smooth! thanks everyone

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post #14 of 15 Old Oct 31st, 2011, 03:56 PM
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Glad to hear!
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post #15 of 15 Old Dec 17th, 2014, 12:45 PM
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2010 Nissan Cube Rough Idle

So, we bought a 2010 Nissan Cube a couple weeks ago. 80,000 miles seemed to run great. After driving it for a while, we noticed a rough idle while sitting at a stop light. Didn't seem to matter if it was in gear of neutral. The RPM's would move between 600 and 1000 and sometimes drop to below 500. It actually stalled at a light once. After much debate and a close inspection I pulled the air filter lid off. the 2 tabs that are designed to hold the filter tight in the housing were worn. This let the filter fall back in the housing slightly leaving about a 1/4" gap between the air filter element and the MAF sensor side of the intake tube. This condition would no allow the air passing the MAF sensor to be consistent, so the computer is constantly trying to adjust. I ran a couple layers of electrical tape around the tabs and re-installed the box lid. Now it holds the filter element tight against the gasket and PROBLEM SOLVED!!! Smooth idle.
I hope this helps someone else.
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