Engine RPM slowly drops @ idle! suggestions???

[whitedragon551 5,000+ posts]

there is no proof though that it didnt happen AFTER i bought the car

If they dont have the paper work saying it would pass emissions and that it wasnt certified there is no proof they didnt sell a faulty car.

 

[SicAudio 5,000+ posts]

exactly they have to prove it can pass an emissions test to sell it even if your area doesn't do emissions. it is a federal law that supercedes all state county ect laws.

 

[adio25 10+ year member]

I'm having a similar problem with my taurus but my car doesn't actually die. I'm thinking its my batt or alt because with the car on, my dome lights have a slight flicker and when i use anything like a window it dims quiet a bit.

 

[whitedragon551 5,000+ posts]

^

Your problem is its a FORD Taurus.

 

[snb778 5,000+ posts]

ok, well it may very well pass an emissions test, just dunno why it sounds like its doing a self check.. does that mean its not?

so I can clean the ICV, can clean the injectors, replace wires, clean Master flow... sounds like a frickin tangled ball of string to me.. i have a feeling this is gonna cost me some money before I get to the bottom of it.

 

[snoopdan 5,000+ posts]

I still bet its the IAC (idle air control valve)

 

[snb778 5,000+ posts]

I still bet its the IAC (idle air control valve)

thats the first thing im going to clean tomorrow, BUT, i was told the ICV wouldn't effect the RPM's while driving...and the RPM fluctuate a little bit while driving also... considering I have this hissing sound, could be a leak somewhere... I just dunno how to find out where.. I don't want to replace the hoses if its not the problem

 

[DBfan187 5,000+ posts]

also get a new PCV valve

 

[SicAudio 5,000+ posts]

Like I said before, and so that others that have no clue about it obviously, the IAC and PCV will not cause driveability issues at higher rpm's and the PCV only affects mileage never drivabilty. (IAC = Idle Air Control I.E. it only affects the idle! PCV is positive crankcase ventilation it runs off vacuum from the motor), you have a bad vacuum leak that you told me about and we discussed it in PM's, fix the leak and see where we are at. do not waste money yet on anything til that leak is fixed. Fixing the leak if it is just 1 small hose , will at most cost you 2-3 bucks for some new line at a parts store. engines run on vacuum, without it, they do all kinds of strange things that seem random. It is a text book sympton. That doesn't mean something else isn't wrong however, but you have to start at key points and not just waste money throwing parts at it.

as well, you can test the spark plug wires easily with a dmm for resistance, you want no more than 5k - 7k ohms per foot; I.E. 3 feet is a maximum of 21k ohms ect.... if it isnt running rough and the rpms are just dipping that isn't even close to being a wire or ignition issue.

here is a test that you can do that will make the engine light come on and verify if the IAC is working. unplug the wire at the IAC on the top or side (depending on what motor you have) of the throttle body housing, look for a silver or black cylinder about the diameter of a toothpaste tube and 2-4 inches long. then try to start your car and let it run. the check engine will come on in 1-3 minutes and when it does you know the IAC is fine, and it will not idle at all on its own ( even worse than it is now with that huge leak you said you have). also you have an OBD II class 3 vehicle computer, it will tell you if you have a misfire issue as well and it does it very fast. just do like we discussed and find and fix the leak. I am betting it is the only problem you have. you may also want to check the vacuum line to the fuel regulator as well. for about 40-80$ you can have most any shop just diagnose it for you which is less than an IAC or plugs and wires and then you wont be throwing good money after bad advice.

let me know what you find //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif good luck.

 

[snb778 5,000+ posts]

sounds good, we'll call it quits there until I get it checked... im just skeptical if a shop does a diagnosis that it wont tell them WHERE i have a vaccum leak

 

[snb778 5,000+ posts]

just cleaned ICV with carb cleaner... do I need to worry about this igniting with a spark somehow, or do I need to carefully clean it out with soap/water now?

 

[snb778 5,000+ posts]

If they dont have the paper work saying it would pass emissions and that it wasnt certified there is no proof they didnt sell a faulty car.

just called em.... they said most used cars are sold "as is" there-for they don't have to warranty anything.. -from the used car manager-

edit: put the idle valve back in after cleaning (didnt look to dirty anyways)... still same problem.. so far Sic is on track

 

[SicAudio 5,000+ posts]

as is dont mean shit bro if it wont pass emissions they have to fix it, and if it isnt running right it will not pass emissions, the law is very clear on it. anything emissions or safety related (like brakes) is a requirement for them to cover under federal law. keep me posted man I will help you do this as cheap as you can.

 

[snb778 5,000+ posts]

whaddya mean brakes to?? my master cylinder was leaking when I bought it, AND one of my caliper pistons is stuck I believe (i'll PM you on that one)... cheap fix, BUT, i had to pay for that to. I would think they would fix anything that could potentially get them in trouble, as dealerships cover their *** with little loop-hole laws and fine print right?

im gettin my new ALT installed tomorrow, they are going to look at the leak in my oil pan and possible replace the gasket if they are already 1/2 way there when the tear everything apart for the ALT.

I was gonna have them do a smoke test to see if there was a vaccum leak, but if the dealership will do it for free then.... i might as well wait to find out if they will first.

 

[SicAudio 5,000+ posts]

smoke tests are for emissions and evap systems not vacuum leaks. propane is used for vacuum leaks, they use propane and when they get close to the leak it kills the motor. then they find the leak and repair it. and yes they are required by law to fix that master cylinder. did you spend about 15 minutes and bench bleed that master cylinder correctly before putting it on the car? if the brakes worked any better before you replaced the M/C , then I suspect the M/C due to alot of air in the lines, a locked caliper wont affect the pedal feel like you describe and you would feel it constantly pull and most likely squeal all the time at the wheel that it is locked.