Idle problem in 5sp, drops to 300rpm

[rmtaylor]

I have about 80,300 miles on my 1992 KA24DE 5-speed, and an idle problem developed after racing a Jetta (and winning). When cold the idle only gos up to about 1000RPM and then does the following when warm. When I pull to a stop and push the clutch in, the idle drops down to 300RPM, stays there for a few seconds, then jumps up to 800RPM and breathes between 800-900RPM. Engine performance is normal. I've done the squeeze test on the lines going to the EGR and the idle doesn't drop when doing so. I have a custom intake with the exhaust recylcing hose on a breather just to mention the environment. Any ideas of what part might be going? Thanks!

[MarketPlayer]

I had a somewhat similar problem as you and i checked the codes on my ECU!  For me it read a bad MAF sensor...replaced it, reset the ecu, and was good to go!  I have one question for you.  Can you rev passed 5K rpm?  I couldn't...Does the xhaust smoke alot when you get on the gas?  is it black smoke?

-zac

[rmtaylor]

The hard part is that there is no check engine light on. I just raced an S2000 earlier today and had it up to 5500-6000RPM easily in 2nd and 3rd. There's no smoke out of the exhaust but it does seem to be burning oddly at idle.

[rmtaylor]

Further diagnosis. After reading this post: http://www.zilvia.net/f....t=11920 and sykikchimp mentioning some carb cleaner, I went to work on a hose coming from the intake. I sprayed about half a can down this tube to the AII valve. It corrected the idle for about 20 miles but now it is back to the bad idle and not looking good. When you squeeze that AII tube the car wants to die. Has anyone had a thorough experience with this problem that can describe to me what action I need to take in order to correct/replace a part for this problem. Thanks!

[fodive]

i had a problem w/ the check engine ligt coming on, and my tach would jump at idle, be very lumpy, and even stall a couple of times...all i did was get some different gas (valero) and then a couple days later changed the feul filter and it runs fine, i dont know what that did, but now im afraid to go to a shell station cause of what it did &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/hmmm.gif" border="0" valign="absmiddle" alt=':hmmm:'>

[jyt747]

Not sure if this is what you did, but check here:

http://www.zilvia.net/f....;t=6639

Here's another solution on 240sx.org faq:

I have a 1991 240SX. I had this idle irregularity problem and took the car to the dealer after I saved some enough money. After several hours of head-scratching, they figured out the IAA valve (which controls the air intake to the fuel injector) was the problem. All they did was to establish an extra grounding wire and also covered the original connecting cable with plastic tape to secure the proper grounding. Now I don't have to fix my eyes to the tachometer each time I press the clutch pedal. It was a really irritating experience and cost about $120, which I think worth it.

Hope this helps...

[sykikchimp]

I'm still ahving this problem.. it seems that after comming to a stop the idle jumps back up to 800 rpms, but stays low 200-300 rpm with the clutch in while rolling.. is that whats happening to you? I'm thinking that the ground may be the problem, since the only thing that changes b/w the idle differences is the rotation of the tires.. possibly excess static buildup is screwing with the ground. anyone with more experience have any input?? I need to play with the grounds. I'm not sure what grounding wire that guy is talking about on the IAA valve either (240sx.org link) So maybe somebody can shed some light and I can finally get rid of this stupid problem.

[rmtaylor]

In regards to JYT747's link to another thread, the post made by WeST:

"The problem is more then likely your AIV (Air Intake Valve)

You AIV is the box located just in front and slightly to the right of your intake box. You should see a tube that connects your intake box to the AIV.

For Diagnostic purposes I would suggest first removing the pipe that connects the intake to the AIV and then start you car to see if it still has a idle problem. If it has changed in its idling behavior then its more then likely your AIV. If it is proceed to the cleaning process below.

The AIV is easy to do. Just take a real hard look at it and find the 4 screws that hold the 2 halves together. Remove the small vacuum line to the top, the larger one, and take the 4- screws off. Pull the top half off and there is a "cap" over the reeds. GENTLY pry the assembly out of the housing. There are 2-sets of reeds. We only did one at a time so we could see how they went back together. Clean this out with a wire brush and a can of carb cleaner. Reassemble and your Idle should be fixed. "

Now is this hose WeST is talking about different from the AAI valve hose that runs under the intake manifold? Cause I just have a breather on what WeST describes. Here is a pic of my breather. I figured it was just a exhaust recycler into the intake:


Sykikchimp: My problem is exactly what you described. Now as far as your theory on the grounding, I have noticed that when I'm stopping with the brake lights on and the car is starting to drop too low on idle...if I let off the brake lights it starts its climb up to 800 quicker than keeping the lights on. I'm clueless when it comes to electricity. I really want to help solve this issue for us!

[sykikchimp]

I think I'm gonna play with the grounding on the IAA valve this weekend and see if I can't figure it out. &nbsp;

The AIV is part of the exhaust recirculation system. &nbsp;I don't think it does much without the vacuum that the intake would give it though. &nbsp;more than likely not the issue.

[rmtaylor]

For some reason it has been somewhat normal the past few days - normalized after I went from 92 to 93 to 94 octane - but still freaks out randomly. Which is not cool because I made an appointment at the dealer for Thursday to have it checked out. I will have more input after then I'm sure. Let us know what you find out this weekend Sykik!

[AzNxbOi23]

My idle problem: When i turn off my Air Conditioning, my rpm drops to around 300rpm from 1krpm. When i turn it back on, it goes right back up, so im pretty sure its related to my A/C. Is this the same as everyone else's? '96 240sx SE 5spd

[rmtaylor]

That is completely normal for the A/C to have the RPMs at 1000. The A/C condensor needs more power than the rest of the components so the engine needs to compensate for idling power. Same thing should happen when the defroster is on. It happens to all cars, not just ours.

[nori tango]

Search function didn't work, I should have posted here. &nbsp;Strange to say but I had similiar problems after one ocassion of driving hard/racing. &nbsp;During idle the rpms would drop and eventually stall. &nbsp;Engine error code read 25: IAC-AAV valve. &nbsp;

From a cheap Chiltons manual: &nbsp;
"The Idle Air Control Valve-Auxiliary Air Control (IAC-AAV) functions by using a duty cycle (on/off/on), which is controlled by the ECM. &nbsp;The longer the "on" pulse, the greater the amount of air that will flow through the valve. &nbsp;The more air that flows through the valve, the higher the engine speed[rpm]. &nbsp;Actual idle speed is the lowest speed at which the engine can operate steadily. &nbsp;This is computed by the ECM, taking into consideration various conditions such as warm-up, deceleration and engine load."

I think that the IACV valve plunger or spring might seize or stick due to dirt. &nbsp;An open intake may accelerate the problem.

The carb cleaner method seem to be a temporary fix and the only way to check for sure is to take the valve out. &nbsp;Can anyone do this without taking off the intake manifold in a 95 240sx?

[rmtaylor]

Well, it went to the dealer last thursday. But of course the 240 stopped acting up a couple days before and they couldn't diagnose anything. They let it sit at idle in the bay for an hour. Blasted! I'm 90% sure its the IAC valve. I'm just going to blast the IAC hose once a week with carb cleaner for a while to clear the stuff out a little at a time. She hasn't surged in a week now. So I think my diagnosis is: clean your IAC line before it acts up! Preventative mainenance that costs $3.00. Might save you $200. &nbsp;<img src="http://www.zilvia.net/f/iB_html/non-cgi/emoticons/thumbs-up.gif" border="0" valign="absmiddle" alt=':thumbsup:'>

[sykikchimp]

</span><table border="0" align="center" width="95%" cellpadding="3" cellspacing="1"><tr><td>Quote (nori tango @ July 13 2002,2:47)</td></tr><tr><td id="QUOTE">The carb cleaner method seem to be a temporary fix and the only way to check for sure is to take the valve out. Can anyone do this without taking off the intake manifold in a 95 240sx?</td></tr></table><span id='postcolor'>
I was wondering the same thing.. I'm not sure how to get in there to the Valve to get the plunger out...

[dsjunkie]

dude i know EXACTLY what you're talking about i had the same exact thing that you're describing in all your posts.... when was the last time you checked your timing chain??....it could be wearing out or loose....that's what happened to me.....it took some serious bucks to replace it but my car ran as clean as a whistle after that, i hope you find out what your problem is cause i couldnt for a while and it pissed the hell outta me

[rmtaylor]

Well, even though my lower timing chain guide is shot and rattling, I don't believe that is the source of the problem. I have full power at all RPMs, and the problem goes away when I clean the AIC line. The car has stopped the idle problem since the last cleaning and is actually getting a smoother power band.

[240Driver39]

alright, just to add to the list and if ne one has a suggestion for me, my idle seems to bounce around a little too. &nbsp;It doesnt happen all the time and i cant really find a pattern for when it does, but sometimes it will idle at the normal rpms, and then take a dive down bout 100-150 rpms, and then come back. &nbsp;It isnt really causing any problems, but somethin about a semi bouncy idle makes me uneasy. &nbsp;u guys just suggest a similiar diagnosis from what has been said?

[twitchy]

how weird is this


i have all these problems and my car wont start if i leave it sit between 30 and 90 minutes. Shorter or longer than that its fine. Inbetween that time period, it always starts up and dies instantly after bogging and choking for a few seconds


even if you floor it it doesnt do a thing

[brett240]

from my expericen it seem the majoirty of problems are coming from the MAF, or the ECU, with the after market intake system since its not a huge difference in idle, your computer may b saying wait a second im not sposed ot b suckin in this much air wuts goin on...but ive worked on a car witha similar problem, it was a mustang and wat fixed the idle problem was changin the parameters on the ecu..just a suggestion