Chriskaw440 Posted January 1, 2008 Share Posted January 1, 2008 1990 SE 5 speed, with most everything new and no codes from the ECU (operating normally....).... quite often now when coming to a stop, and take it out of gear, the idle will jump up to almost 2,000 rpm...and stay there for a few moments...then gradually drop back to normal idle speed.... sometimes it does this, sometimes it doesn't..... I am wondering if it could be MAF sensor dirty?? (looks clean, but I dont know much about them as I have never had to do anything with MAF's and have no idea how to clean them properly...) or the Neutral switch? All vacuum hoses are new and correctly connected, fully tuned and soforth.... K&N cone type air filter. it idles very smooth both at normal and when it races up when in neutral......I can sometimes feel the engine wanting to rev back up just before it's taken out of gear and then when I release the clutch, sure enough it races up and then gradually goes back down to normal. It has done this on occassion even before I did my full tune and knock sensor replacement, and O2 sensor, so I doubt it is related to any of those things. It's kind of a waste of gas for one thing, and kind of embarassing when sitting at a stop light with the engine revving so high while the person in the car next to me looks over with a puzzled look on their face (no I dont wanna race you, my stupid idle wont go down.....) any ideas or anyone else familiar with this happening on their rides? thanks all, Chris (and don't anyone tell me it's being caused by one of my lug nuts....I'm slow sometimes... but not THAT slow....) Happy New Year!! Link to comment Share on other sites More sharing options...
95shakinPF Posted January 1, 2008 Share Posted January 1, 2008 Take a look in the how-to's and read up on cleaning the throttle body and MAF sensor. I'll bet a paycheck thats your troubles!! Good luck! Link to comment Share on other sites More sharing options...
88pathoffroad Posted January 1, 2008 Share Posted January 1, 2008 Throttlebody or idle air control valve setup being crusty, perhaps. Link to comment Share on other sites More sharing options...
msavides Posted January 8, 2008 Share Posted January 8, 2008 (edited) Mine does the exact same thing. It is a 91 SE Manual transmission. I was told this is normal, I don't think it is. Since It has always done it, I have lived with it. I have tried swapping the MAF sensor, I have like you replaced everything, Spark plugs, wires, cap,rotor,ect Mark Edited January 8, 2008 by msavides Link to comment Share on other sites More sharing options...
Chriskaw440 Posted January 8, 2008 Author Share Posted January 8, 2008 Mine does the exact same thing. It is a 91 SE Manual transmission. I was told this is normal, I don't think it is. Since It has always done it, I have lived with it. I have tried swapping the MAF sensor, I have like you replaced everything, Spark plugs, wires, cap,rotor,ect Mark Hi Mark, I don't think its normal either....so whoever told you that should be beaten with a sack full of hammers Most everything tune-up wise is new on my pathy, new plugs, cap/rotor, knock sensor, O2 sensor, gaskets, etc etc... I had a nissan mechanic tell me once that he thinks my "neutral switch" is bad but at the time I didnt know what he meant so I just ignored it. (he never would say WHY he thinks its bad, just said it was....) Since it happens mostly when its taken OUT of gear, I am wondering if he was onto something, I know from past experiences on other cars, if the IAC valve starts going bad, they cause the idle to be really crappy and noisy and thats not my case here. I havent cleaned my MAF sensor yet but thats my next step I have no error codes and engine runs beautifully otherwise, with over 240,000 miles on it. vacuum hoses are all new also. just one of those annoying things I guess to figure out. -Chris Link to comment Share on other sites More sharing options...
msavides Posted January 8, 2008 Share Posted January 8, 2008 (edited) Hi Mark, I don't think its normal either....so whoever told you that should be beaten with a sack full of hammers Most everything tune-up wise is new on my pathy, new plugs, cap/rotor, knock sensor, O2 sensor, gaskets, etc etc... I had a nissan mechanic tell me once that he thinks my "neutral switch" is bad but at the time I didnt know what he meant so I just ignored it. (he never would say WHY he thinks its bad, just said it was....) Since it happens mostly when its taken OUT of gear, I am wondering if he was onto something, I know from past experiences on other cars, if the IAC valve starts going bad, they cause the idle to be really crappy and noisy and thats not my case here. I havent cleaned my MAF sensor yet but thats my next step I have no error codes and engine runs beautifully otherwise, with over 240,000 miles on it. vacuum hoses are all new also. just one of those annoying things I guess to figure out. -Chris so yours is a auto transmission? To my knowledge Manual transmissions do not have a neutral switch. They have a switch on the clutch to prevent the truck from starting with the clutch not press but that is about it. Mark Edited January 8, 2008 by msavides Link to comment Share on other sites More sharing options...
Chriskaw440 Posted January 9, 2008 Author Share Posted January 9, 2008 so yours is a auto transmission? To my knowledge Manual transmissions do not have a neutral switch. They have a switch on the clutch to prevent the truck from starting with the clutch not press but that is about it. Mark nope mine is a 5 sp manual also...... thats why the nissan mechanic (or maybe idiot....) had me confused when he told me my neutral switch was bad.....'cause I didnt think the manual trannys had one.... but to be honest I am not 100% sure. I may have to break out my Hanes and Chiltons manuals to look it up. Link to comment Share on other sites More sharing options...
Kittamaru Posted January 14, 2008 Share Posted January 14, 2008 I have the exact OPPOSITE problem on an automatic... my idle drops to below 500... it'll dip as low as 250 some times, rumble real gutteral like, and kick back up to around 500 where, I presume, it should be. Link to comment Share on other sites More sharing options...
msavides Posted March 11, 2008 Share Posted March 11, 2008 nope mine is a 5 sp manual also...... thats why the nissan mechanic (or maybe idiot....) had me confused when he told me my neutral switch was bad.....'cause I didnt think the manual trannys had one.... but to be honest I am not 100% sure. I may have to break out my Hanes and Chiltons manuals to look it up. Update! I have fixed my problem. turns out my iac was all gummed up. cleaned it up with some seafoam. then ran it through the tank. Mark Link to comment Share on other sites More sharing options...
Simon Posted March 11, 2008 Share Posted March 11, 2008 I have the exact OPPOSITE problem on an automatic... my idle drops to below 500... it'll dip as low as 250 some times, rumble real gutteral like, and kick back up to around 500 where, I presume, it should be. Yours could very well be the connection to the MAF sensor. It's pretty common to be a little flaky on these things. Link to comment Share on other sites More sharing options...
Kittamaru Posted March 11, 2008 Share Posted March 11, 2008 Nope, my connection is secure - I have jiggled every wire and connection I can get my paws on, no difference It sounds like it's coming from the rear end... Link to comment Share on other sites More sharing options...
Chriskaw440 Posted March 11, 2008 Author Share Posted March 11, 2008 Update! I have fixed my problem. turns out my iac was all gummed up. cleaned it up with some seafoam. then ran it through the tank. Mark ok ...sounds logical....but the IAC is located under the plenum (damnit) ....so how did you clean it? I figure I'd have to take the plenum off again since I just did a knock sensor job a few months ago, and you know....I considered just replacing that IAC while I had everything taken apart but I saw that they are somewhat expensive so I just left it as is.... How much seafoam goes into the tank? I assume into a full tank of gas.... I have never used the Seafoam stuff before. Link to comment Share on other sites More sharing options...
msavides Posted March 11, 2008 Share Posted March 11, 2008 (edited) ok ...sounds logical....but the IAC is located under the plenum (damnit) ....so how did you clean it? I figure I'd have to take the plenum off again since I just did a knock sensor job a few months ago, and you know....I considered just replacing that IAC while I had everything taken apart but I saw that they are somewhat expensive so I just left it as is.... How much seafoam goes into the tank? I assume into a full tank of gas.... I have never used the Seafoam stuff before. The IAC is on the side of the plenum. I was messing with my injectors and had the plenum off anyways, but it seems like it could be removed without the plenum removal. this is the first time I have used it as well. I had used every other injector cleaner under the sun and it did nothing. The seafoam actually made the most difference. I used half a can with a half a tank of gas. But I guess a full tank and a full can should be better. It proved to me that I had a leaky injector since when the truck would sit for a few days the gas would evaporate off and leave the seafoam. when I would start it up after sitting a cloud of white smoke would come out of the exhaust. It did more than just prove the injector was leaking. by the time the tank was empty it had cleaned out whatever was in my injector causing it to leak. Now it consistently idles at 700-750. I have heard lots of people swear by the stuff I was skeptical. I would try the seafoam first and then if that does not work then mess with the IAC. Mark Edited March 11, 2008 by msavides Link to comment Share on other sites More sharing options...
ILoveMyPatty Posted March 13, 2008 Share Posted March 13, 2008 Time for me to try some seafoam, if these vac lines don't fix it. Link to comment Share on other sites More sharing options...
msavides Posted April 22, 2008 Share Posted April 22, 2008 (edited) Another Update! My Pathfinder started acting up again. This time I decided to tear The intake apart for the last time. I removed it completely then removed all the components off the intake and gave it a good dousing with carb cleaner. I had to scrape the egr tube since it was so gummed up and caked. I decided to replace the AAC (IAC valve)($150.00 at rock auto) I also gave it another sea foam vacuum line treatment just for good measure after reassembly. I then did the adjustment for the AAC as described in the Factory manual and it has been idling exactly at 750 ever since. Lets just hope this fix is more on the permanent side. Mark Edited April 22, 2008 by msavides Link to comment Share on other sites More sharing options...
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