Chriskaw440 Posted February 5, 2010 Share Posted February 5, 2010 Hi all, Sometimes when I come to a stop, or just coasting along like through a parking lot, out of gear, my idle will jump to about 2,000 rpm.....then gradually creep back down to normal (650-700'ish rop) I know the valve is there to kick in when additional load is placed on the engine such as AC on, or power steering load....to feed more air to the intake. So I'm thinking its cutting on when it doesn't need to...my ac doesn't work anyway LOL. Doesn't do it all the time, just occasionally...which of course is a waste of gas, and makes it harder to shift into first gear. Tapping the gas pedal or riding the clutch a little doesn't lower it....it's always gone back down just on its own..... Is that typically the Idle Air Control Valve going wacky? (and for all I know its the original one) I hear they can get carbon filled with age. Everything else related to idle operation seems to work fine. No vacuum leaks that I can find anywhere either. I want to go ahead and order a new one but since they are about 140 to 150 bucks, I wanted to get some opinions first. I want to replace it if thats the general consensus when I do my drivers side lifters since I have to take the plenum off anyway...and the stupid thing is under the plenum. thanks! -Chris Link to comment Share on other sites More sharing options...
andreus009 Posted February 7, 2010 Share Posted February 7, 2010 Well, I don't have a solution but I have had a similar issue. Sometimes it will do it two or three times in a week but then not do it again for a month or two. Kind of weird. It has been so infrequent that I never bothered to try to figure it out. If there is a way to electrically disable the Control Valve to see if it stop the issue before replacing it. Just a thought. Link to comment Share on other sites More sharing options...
str8andnarrwpath Posted February 8, 2010 Share Posted February 8, 2010 i have a similar problem,check to make shure your fan free spins when engine is cold. if it spins all the time could be stuck on? or getting to the stage where it will be stuck on. does the engine take a while to warm up? mine does. i dont know if its a fix or replace thing, maybe its a common problem? hope this helps Link to comment Share on other sites More sharing options...
BoneZ Posted February 12, 2010 Share Posted February 12, 2010 I Have the same problem with mine when it happens it happens at startup. Let us know if you figure it out. I have been thinking it is the IAC to but dont want to pull the intake to find out i am wrong. Link to comment Share on other sites More sharing options...
Chriskaw440 Posted February 19, 2010 Author Share Posted February 19, 2010 I'm about to order a new IAC and the rest of the lifters need to finish replacing all the hydraulic noisy 250,000+ miles on 'em lifters. Will let you know how it turns out idle-wise. -Chris Link to comment Share on other sites More sharing options...
unccpathfinder Posted February 19, 2010 Share Posted February 19, 2010 check the EGR valve's rubber tubes...one may be "cracked" in half its hte short J tube...my 95 had it and i didnt find it until i did my swap...i would get some bad idles and then sometimes it would idle up at 1400 or so RPMs but don't second guess the IAC b/c i have an issue with that too but it tries to make my truck stall on cold days until it gets warm Link to comment Share on other sites More sharing options...
PATHRIDER Posted February 24, 2010 Share Posted February 24, 2010 (edited) IAC is Idle air controller? Edited February 24, 2010 by PATHRIDER Link to comment Share on other sites More sharing options...
Chriskaw440 Posted February 24, 2010 Author Share Posted February 24, 2010 check the EGR valve's rubber tubes...one may be "cracked" in half its hte short J tube...my 95 had it and i didnt find it until i did my swap...i would get some bad idles and then sometimes it would idle up at 1400 or so RPMs but don't second guess the IAC b/c i have an issue with that too but it tries to make my truck stall on cold days until it gets warm Sure enough I did find a crack in the vaccume line right where it slips onto the egr (dry rotted).....I just wrapped it tightly in electrical tape until I can get to the parts store to buy more vaccum tubing...seems to be a little better but I'm also still replacing the original IAC valve because I DO NOT want to have to take the plenum off again anytime soon LOL. I can tell it is still not operating quite right anyway. thanks for that tip Link to comment Share on other sites More sharing options...
unccpathfinder Posted February 26, 2010 Share Posted February 26, 2010 good stuff...yea it helped mine too but i still think i need to pull the IACV off and like you I don't want to pull the upper intake off so i've been putting it off for as long as possible Link to comment Share on other sites More sharing options...
msavides Posted February 28, 2010 Share Posted February 28, 2010 I replaced my IAC valve with a new one. However it did not help mine. I think I may have a different problem, I also get a code 45 (leaking injector) I have replaced all of my injectors with refurbished ones and I still have the same problem. I am still stuck. I have also changed my o2 sensor and my MAF sensor. Not sure what to try next. Mark Link to comment Share on other sites More sharing options...
Chriskaw440 Posted March 3, 2010 Author Share Posted March 3, 2010 I replaced my IAC valve with a new one. However it did not help mine. I think I may have a different problem, I also get a code 45 (leaking injector) I have replaced all of my injectors with refurbished ones and I still have the same problem. I am still stuck. I have also changed my o2 sensor and my MAF sensor. Not sure what to try next. Mark Just finished my project with replacing all the hydraulic lifters and the IAC (also called AAC) valve, and a whole bunch of vacuum lines, and while I had the plenum off I also replaced all the spark plugs because it was SO EASY with the plenum out of the way. My air intake tube also had a big split in it near the air filter end of it and I just cleaned it really good and used silicone sealant around it and let it sit for 24+ hours to dry. Made a nice flexible seal on it. Since this thing is rubber, and over 20 years old, I wasn't surprised to find the big split and I am sure it was letting in air. Cranked it up.....smooth as a kitten purring. Drove to the gas station to fill up....my Pathy has never run this smooth before and I have had it since 2001. Keeping my fingers crossed that it stays this way!!! Link to comment Share on other sites More sharing options...
msavides Posted March 3, 2010 Share Posted March 3, 2010 Just finished my project with replacing all the hydraulic lifters and the IAC (also called AAC) valve, and a whole bunch of vacuum lines, and while I had the plenum off I also replaced all the spark plugs because it was SO EASY with the plenum out of the way. My air intake tube also had a big split in it near the air filter end of it and I just cleaned it really good and used silicone sealant around it and let it sit for 24+ hours to dry. Made a nice flexible seal on it. Since this thing is rubber, and over 20 years old, I wasn't surprised to find the big split and I am sure it was letting in air. Cranked it up.....smooth as a kitten purring. Drove to the gas station to fill up....my Pathy has never run this smooth before and I have had it since 2001. Keeping my fingers crossed that it stays this way!!! you didn't happen to have any codes or check engine lights did you ? Link to comment Share on other sites More sharing options...
Chriskaw440 Posted March 11, 2010 Author Share Posted March 11, 2010 you didn't happen to have any codes or check engine lights did you ? Well honestly I haven't gotten to check for any codes yet ....been a very busy week. I plan on checking this weekend. Since then though it has on occasion gotten stuck on high idle again but for shorter length of time.....darnit!!!!! Still much better than it was before...but....still more checking to do I guess. New IAC, new hoses(vaccum), plenum gasket, spark plugs, lifters.. Do these have "neutral switches" ?? mechanic told me once I need a new one but I have no clue where it would be or even if a 1990 5 speed has one.... -Chris Link to comment Share on other sites More sharing options...
msavides Posted March 12, 2010 Share Posted March 12, 2010 Well honestly I haven't gotten to check for any codes yet ....been a very busy week. I plan on checking this weekend. Since then though it has on occasion gotten stuck on high idle again but for shorter length of time.....darnit!!!!! Still much better than it was before...but....still more checking to do I guess. New IAC, new hoses(vaccum), plenum gasket, spark plugs, lifters.. Do these have "neutral switches" ?? mechanic told me once I need a new one but I have no clue where it would be or even if a 1990 5 speed has one.... -Chris only switches I know of in a MT is the interlock switch and the clutch safety switch. The interlock bypasses the clutch switch so you can run the starter without pressing the clutch and the clutch switch will not let you crank the starter if you do not have the clutch pressed. I bypassed my clutch switch for my remote start alarm system. Link to comment Share on other sites More sharing options...
PATHRIDER Posted March 12, 2010 Share Posted March 12, 2010 wouldnt that be dangerous..how if you remotely start it and its in gear Link to comment Share on other sites More sharing options...
PATHRIDER Posted March 12, 2010 Share Posted March 12, 2010 I replaced my IAC valve with a new one. However it did not help mine. I think I may have a different problem, I also get a code 45 (leaking injector) I have replaced all of my injectors with refurbished ones and I still have the same problem. I am still stuck. I have also changed my o2 sensor and my MAF sensor. Not sure what to try next. Mark wonder if it has anything to do with the TPS? Link to comment Share on other sites More sharing options...
Chriskaw440 Posted March 12, 2010 Author Share Posted March 12, 2010 wonder if it has anything to do with the TPS? Well I just went out to check for any codes and I got "55" which means no malfunctions (at least as far as this old type system can detect LOL) and then let it warm up and sure enough it started acting funky again with the idle....speeding up erratically and such....when I put my hand on the throttle cable linkage and reved it just a tad it would settle down....then act up....etc etc. I removed the small vacuum line from the intake tube and shot about half a can of carb/intake cleaner while working the throttle some so it wouldn't konk out and then let it run for a little bit....seemed to be normal again so I am hoping it is just build up on the throttle plate/intake stuff. TPS is what I am looking into since everything else checks out and all vacuum lines and such are good and in the right places. We'll see how it runs today when I head out later -Chris Link to comment Share on other sites More sharing options...
PATHRIDER Posted March 12, 2010 Share Posted March 12, 2010 seafoam Link to comment Share on other sites More sharing options...
Chriskaw440 Posted March 12, 2010 Author Share Posted March 12, 2010 seafoam Helllll no I'm not putting any more seafoam in my engine LOL. The throttle body cleaning I sprayed in seems to have helped quite a bit...drove around today and it barely wanted to do the erratic idling. BUT, Im pretty sure it has to do with the throttle body or TPS, because when it would start acting up, I would just barely tap the gas pedal, kind of like when I just tapped on the throttle linkage with my hand, and it would immediatly drop down to normal idle. Not 100% positive but just saying....those are my reports so far! -Chris Link to comment Share on other sites More sharing options...
msavides Posted March 13, 2010 Share Posted March 13, 2010 wouldnt that be dangerous..how if you remotely start it and its in gear the alarm makes you go through multiple hoops on fire in correct order before it will let you remote start it.. before i park my truck. I have to set the parking brake hit the button on my remote then turn off the ignition and remove the key. then without touching anything else i have to exit the truck. the truck locks and arms. then and only then will it remote start. if i open the truck door before remote starting it will not remote start. Kinda a Pita so i hardly use it, still nice to know i can if i want to. It did not cost be any extra for the remote start function. Link to comment Share on other sites More sharing options...
msavides Posted March 13, 2010 Share Posted March 13, 2010 (edited) wonder if it has anything to do with the TPS? I have a brand new one. Maybe I will give it a try. Edited March 13, 2010 by msavides Link to comment Share on other sites More sharing options...
Chriskaw440 Posted March 15, 2010 Author Share Posted March 15, 2010 I have a brand new one. Maybe I will give it a try. Since spraying the carb/intake cleaner into the air intake tube while engine running (pretty much a full can worth)....Mine has NOT gotten stuck on high idle since. (I just used off the shelf carb/intake cleaner...not seafoam or any other 'specialty' product) Link to comment Share on other sites More sharing options...
Chriskaw440 Posted March 16, 2010 Author Share Posted March 16, 2010 Since spraying the carb/intake cleaner into the air intake tube while engine running (pretty much a full can worth)....Mine has NOT gotten stuck on high idle since. (I just used off the shelf carb/intake cleaner...not seafoam or any other 'specialty' product) UPDATE: damnit....tonight it started idling high again......gggrrrrrrrrrrrrrrr.....still not as often but....enough to piss me off Link to comment Share on other sites More sharing options...
msavides Posted March 16, 2010 Share Posted March 16, 2010 UPDATE: damnit....tonight it started idling high again......gggrrrrrrrrrrrrrrr.....still not as often but....enough to piss me off sound like it is similar to what I am going through. except I get a code 45 leaking injector. I have cleaned out all carbon from the entire intake. it behaves for a couple of weeks and then acts up. I get the high idle then sometimes I get a low idle like it wants to die. I am baffled Link to comment Share on other sites More sharing options...
PATHRIDER Posted March 16, 2010 Share Posted March 16, 2010 Have you guys tried replacing the TPS? Link to comment Share on other sites More sharing options...
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