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1996 Kia Sephia GS
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120 Posts
Discussion Starter #1
New problem, had no issues previously other than a few dash lights not working all the time.

This happened last night very bad and once more but has not happen again. I can be driving anywhere between 0-55, when I let go of the gas the RPMs drop immediately to 200 or so and it bobbles down around 200. Happens when at a stop as well. When this happen and I stopped the car and put it into park the RPMs jumped up to about 1400 then back down to 750 that was a 1st as well.

Cant word the search right all I am finding online is things related to AC or brake issue. Mine has nothing to do with those, AC is off im doing nothing but taking my foot off the gas pedal.

The car also seems to be running rich all of the sudden. Checking what I can today for vacuum leaks, changing air filter. I have a fuel filter but dont think that is the problem.

So to recap, foot off the gas pedal RPMs drop instantly to 200. Car has not stalled out on me yet.

Thanks all for the input!
 

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2008 SpectraSX, 2014 Optima LX,2006 Jeep Liberty, Linux Mint Mate
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When you remove your foot from the accelerator the engine should return to idle. On newer cars there is a device called an IAC (idle air control) valve. It's purpose is to constantly adjust the idle speed of the motor by varying the amount of air being fed to it. Your car is 17 yrs old and probably hasn't had the IAC cleaned in a long time. They will stick and can idle high or low. If you turn on the ignition but not start the car and then search for a device under the hood that is "buzzing" back on the aluminum "tube" you found the IAC... It will need cleaned with carb/choke spray... If it's not wore out things should return to "normal". Do a Google search on "cleaning the IAC".
Vacuum leaks are also common on older engines. look for cracks in the large rubber hose and for cracked/brittle small rubber hoses...When was the last time the spark plugs were changed? Worn out plugs will cause poor mileage as will dirty air filters...These may or may not solve your problems but are good to look at..
Dave
 

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1996 Kia Sephia GS
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120 Posts
Discussion Starter #3 (Edited)
Ill give the IAC a cleaning. Ive done it a few times on other cars as a way to rule it out as a problem. Hopefully itll rule it out here as well :)

Normally when driving 45mph at 2000 or so RPMs if I let off the gas it drops only a few hundred, sometimes down to about 1000 but its a nice steady drop. This new problem, when it happens you can feel the car burbling (if thats a word) and the rpms dont go down nice and easy they just fall down to 200 which is about 550 less than idle.

Car has only done it when I was driving twice, once 2 days ago driving a short distance and again last night on the way home from work. (only about a 6 mile drive, it started halfway home I could feel it doing the burble when driving)

My IAC or ISC (not sure which it is, my haynes said ISC but it seems to do the same as IAC and you can clean it the same way) is connected to the MAF, different from my other cars. But seems to still come off with just 2 or 3 bolts.

Will use the black RTV sealant after cleaning instead of a new gasket as I have no money :) Ive used it before on my IACs and water pumps should be fine.

Spark plugs are the same, I got the car 3 months ago and gave it a tune up. I may pull them out to make sure they are not fouled. When I got the car all the plugs were worn even and nothing abnormal about them at all. (which again was odd, every car ive bought used has been too hot, had some oil or some kind of issue with the plugs but this car is ok so far)

Ive changed the oil twice in 3 months, first time the oil was thick black and nasty, when you looked into the oil cap it was black and thick. 2nd time was the same, now you look and you can see shiny metal and clean oil so I am guessing thats been cleaning itself out.

I have yet to find any vacuum leaks, used one of those tube stethoscopes to search as well as a wet hand and used carb spray around the engine. No jumping idle and no hissing no air felt.

I am fairly sure by the sound of it I am leaking exhaust somewhere along my exhaust pipe. It sounds as if its coming from near the center of the car. Took it into a shop to test my cat and they said cat was fine no other problems detected except higher than normal back pressure when the car is turned off. But still within limits of being fine. (no clue what that means)

I do know my brake resivour is leaking from that metal pipe/nut directly under the filler box but ive read that is very common with this car. The replacement parts will end up doing the same so I have not fixed that yet as I plan to replace that whole section not just tighten it up. It seems to be dripping onto just the body parts under it, no wires or plug connections.

Thanks for input! I will clean IAC tomorrow. I wont know if this fixes the problem as I cant duplicate it at will but give it a week or so and it should tell. Any other ideas are greatly appreciated!

Ive also found if its doing the 200 rpm burbling if I turn the car off, turn it back on it fixes that problem 50% of the time (cars done it twice, it fixed it once other time it did not but the problem was gone next morning when I went to work)

Again, thanks!

*edit*
I may of been off, there might be an ISC and IAC BELOW that. I was wondering why it looked so wonky :p Will clean IAC tomorrow.
 

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1996 Kia Sephia GS
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Discussion Starter #4 (Edited)
As most I forgot to update the thread when I fixed my problem.
(I was never able to buy an air filter locally, ended up buying one months later from rockauto. 2 of the same filters, 1 is orange and looks like it was left out of the box for months, different brand and number box with a sticker over the numbers, very dirty foam and the injection process screwed up, some bigger V gaps, about 80% of the filter is right. Then the other filter must of been a premium, it looks perfect, black foam and when I put it in I actually had to run my thumb around the border to seat it perfect because the foam actually fills the area now, not just sits in)

Ive never heard of it before but my air filter was the cause. Looked clean but must of been clogged up good.


Took it out, banged it on the hood put it back and the car ran fine, rich smell was gone. Had to do this about once a week, I vacuumed the filter and it was good for 3 more months. Ive been cleaning it every few weeks, just got a new filter from rockauto, little more pickup when stepping on the gas.

(I did clean IAC, no difference when I did that)

I am sure ill post up more problems here soon, just got my check engine light and its o2 , vacuum leak or maf and exhaust purge solenoid =/ Atleast I got to go buy one of those extremely nice OB2 scanners :) Live data does me no good because I dont understand it but its still fun to be able to bring it up :p
 
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