dr_bowtie Posted February 9, 2007 Posted February 9, 2007 Umm...what model car? Sounds a bit like a bad EGR valve. Are you experiencing any other symptoms like rich gas mixuture (tell tale sign would be black smoke out of the tail pipe), bad fuel economy, crappy response from the engine...etc? EGR valve stands for Exhaust Gas Recircultion.... So if the valve was hanging open then you would have a lean mixture...not a rich one... you would be filling the chamber with more exhaust gases then normally allowed.. This makes for a very rough idle..because of the lean condition...not to be confused with a vacuum leak...because it's not...it recirculates exhaust gases back into the intake tract and attempts to reburn the unburnt gases... this effect reduces some emission at the expence of higher cylinder temperature... most of the time a EGR valve can be cleaned and put back into service...very rarely do they ever go bad...fyi EDIT: in addition to CPDMF... if you suspect a vacuum leak you can quickly detect it by doing a simple test...using a can of carb cleaner...lightly spray around the intake manifold mating surfaces and tubes...if you hit the leak with the spray the rpm will come up and hold steady for a split second (until the spray mist is gone) With a vacuum leak you may get some oscilation but it will be more spread apart...a much slower pace and usually not a big drop in rpm unless it's a big vacuum leak which can be detected by a hissing noise comming from other than the air inlet.... pay attension and listen... You either have a severe vacuum leak or a faulty IAC solenoid.... With the faulty IAC the rpm oscialtion will be pretty rapid...almost faster than you could mimick it by petal manipulation... Share this post Link to post Share on other sites More sharing options...
TaterSalad Posted February 9, 2007 Posted February 9, 2007 my MAS has been sounding like its sucking air, think its faulty? all intake tubes are newer/no cracks. no check engine light unless it stalls. once i touch the gas it runs smooth, and i dont power brake, i just shift into neutral when i have to stop, and keep my foot on the gas a bit Share this post Link to post Share on other sites More sharing options...
dr_bowtie Posted February 9, 2007 Posted February 9, 2007 then it's the IAC... a vacuum leak would still make it run a little rough once it idles up a little bit... You should here the hissing sound from the MAS because it's inline straight from the air inlet...but check the ducting from the air inlet box to the MAS and from the MAS to the engine inlet (throttle body) make sure there are NO cracks in the tubes... especially the one from the MAS to the throttle body... If there are alot of miles on the car you may want to think about replacing the TPS (throttle position sensor) the IAC works in relation to the TPS and if it's bad the IAC will be inacurate... Share this post Link to post Share on other sites More sharing options...
TaterSalad Posted February 9, 2007 Posted February 9, 2007 we checked everything on the intake, no cracks, no leak. but when i say it sounds like its sucking air its loud, i started up my moms strait 4 and heard nothing from the MAS, and my sisters inline 4 and nothing. also, when we adjusted the idle/mixture screw it would get louder when pushing the screw in, and quieter when pulling the screw out. while the idle would not change at all. Share this post Link to post Share on other sites More sharing options...
dr_bowtie Posted February 9, 2007 Posted February 9, 2007 thats because the IAC is trying to over compensate for the mixture change... All the IAC is...is a controlled vacuum leak....thats all...and when the rpm oscialates on it's own...so doesn the hissing sound... because the IAC is acting funny.. you see the IAC is supose to move several hundred times a second... when it starts to go bad it may adjust much less...and you will hear hissing... if you do and internet search you will be able to find test procedures with voltages to test for...... I would pull the IAC out and check for debris in the passage... you will get buildup that will stop it from closing completely... clean it inside and out...then re-install the IAC and tuen the key on and off several times...leaving it on each time for 5 to 10 seconds... this will set the IAC at default.. and then restart the vehical... if it still oscilates the IAC itself maybe faulty... Share this post Link to post Share on other sites More sharing options...
TaterSalad Posted February 9, 2007 Posted February 9, 2007 ok, thanks when i turn the car on and off am i starting it, or just putting it in the on position? Share this post Link to post Share on other sites More sharing options...
momoceio Posted February 9, 2007 Posted February 9, 2007 On position... Share this post Link to post Share on other sites More sharing options...
dr_bowtie Posted February 9, 2007 Posted February 9, 2007 correct...on position only... then start it after the 5th time... Share this post Link to post Share on other sites More sharing options...
TaterSalad Posted February 9, 2007 Posted February 9, 2007 ok, thanks:D i found the test procedure in my book, hopefully this will fix it and i can move on to why my windows fog up like crazy. lol Share this post Link to post Share on other sites More sharing options...
dr_bowtie Posted February 9, 2007 Posted February 9, 2007 windows fogging like crazy can be 2 things....A leaking heater core...if the fog taste sweet...it's the heater core... OR the AC not running when in defrost mode...the AC is a dehumidifier and pulls the moisture out...if it's not running it's not defrosting the windows... check to make sure it's circulating... Share this post Link to post Share on other sites More sharing options...
Guest LookBackX2 Posted February 9, 2007 Posted February 9, 2007 Just noticed this thread, if you havn't checked the barage of sensors on the intake side, then I definately agree with dr_bowtie. It is most likely a MAS, Manifold Absolute Pressure Sensor, IAS, or if it is leaning out then stalling, and not stalling from a rich mixture, AFTER and I mean after you check the sensors, try the EGR valve, and solenoid. And if you have a pressurized loop cooling system, for kicks check the resistance of your Coolant temp Sensor. That includes using pot of water, digiMM, and thermometer. Fun Stuff. But to the point, if it is supplying the wrong resistance @ the correct temp OBD 1 can not adjust or warn you that it conflicts with the rest of the sensors readings. I say if the problem isn't apparent, and you have a pre-96 car (as in your case) especially if it is a Ford MoCo built car, run away. or spend hours upon hours of testing to find a short in the wiring harness:sad: From there I would be suspicious of the computer starting to die. It just seems real strange with the symptoms described, that the car would be on a lean mixture. That usually causes a slight increase in rpms, not a "bogging" behavior. you get that from a rich mixture, and a sweeeet smell that can burn your nose. A lean mixture will smell more like roasted almonds. I'm tired and just about to go to bed, so no proof read. Take these ramblings as just that. But if anything I've typed ends up hlping, great. Best of Luck M8 Share this post Link to post Share on other sites More sharing options...
TaterSalad Posted February 9, 2007 Posted February 9, 2007 windows fogging like crazy can be 2 things....A leaking heater core...if the fog taste sweet...it's the heater core... OR the AC not running when in defrost mode...the AC is a dehumidifier and pulls the moisture out...if it's not running it's not defrosting the windows... check to make sure it's circulating... i checked the heater core when it first started fogging and didnt see any leaks, but im gonna check again tomorrow. and i have to run the ac full time to keep it so i can see out my windows, and sometimes it doesnt seem to help. i did have a leak in my trunk, but that is dried up now. @LookBackX2 thanks for the ramble(lol), i will be sure to check all that if nothing suggested works. Share this post Link to post Share on other sites More sharing options...
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