Engine stutters heavily when idle - Kia Forum

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post #1 of 13 (permalink) Old 06-19-2007, 12:45 AM Thread Starter
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Unhappy Engine stutters heavily when idle

Hello everyone!

I read a lot around the forums and found many similar problems, but none quite exactly like mine.

It all started with a slight stutter when the engine was running at low rpm's or when idle. I noticed that sometimes while driving on a highway at around 60 mph, if I stopped accelerating (just let go of the pedal), the engine would sometimes stall completely (shut off).

The problem was random. Sometimes the engine would stutter when idle, sometimes it would run smoothly. Every once in a while, when the engine stuttered, it would stall completely as well.

When idle, tapping on the accelerator once to make the rpm's increase would increase the chances of the engine stalling when the rpm's decreased again.

The problem seemed to be less occurring when the A/C was turned on, as the rpm was slightly higher than when it was off. The engine would still stutter, but rarely stall.

Eventually, the problem got worse to the point that every single time the engine is either idle or at low rpm, the engine stutters heavily and often stalls, unless you accelerate it even if just a tiny bit.

Last Thursday, I was checking out the engine with my dad. We were thinking about uncovering the air filter when two pricks mugged us Right before that, we had disconnected a cable from the air filter. I have no idea what it is. I saw two connectors close together, we had removed the upper one.

After the incident, we decided to move the car back into the garage and just quit checking it. At the moment, we didn't realize the engine didn't stutter...

Next morning, after realizing the above mentioned, I did some testing. The engine would stutter with the cable connected, but not with the cable disconnected. I was happy because I thought I had found a workaround.

Later, we noticed that even though the engine didn't stutter, once in a while it would suddenly stall completely. When it did, it was hard to turn the engine back on, and when it did, it would stall again in less than 3 seconds unless we revved the engine a bit. Then it would work "normally" again at either idle, low rpm or high rpm. I did notice that when trying to start the engine, sometimes (rarely) I could hear a loud, deep and somewhat hollow thud coming from the engine. It seemed to come from the air filter, like something was exploding in there.

The engine was making a rattling noise. We checked the oil and it was very low, so we bought some and filled her up. I'm pretty sure I poured a tiny bit too much oil (oops). A few miles later, the engine began stuttering VERY heavily (more than ever) at low rpm's and almost always stalling when idle.

At this point, whether or not the cable from the air filter is connected makes no difference at all. Again, this ONLY happens at low rpm's or when idle. Otherwise, the engine runs pretty darn good and pretty darn fast.

I tried tapping what I think are the IACS and TPS, as I read something about that, but no change is noticeable.

Another question: The O/D function is not working. Thankfully, I can't switch it off (it would be bad if I couldn't switch it on, eh ? ). Any ideas on this ?

I've seen how great you guys are at giving advice. I can only hope for the best. I love my Sephia, and I hate that it's going through this. I am aware I haven't given my car the maintenance it deserves. I've given it NO maintenance actually, for economic reasons. This only shows me how great this car is. No maintenance and yet this is the only major problem it has.

Thank you all in advance. I'm sorry I made such a long post, but I'm trying to give as much detail as possible to get more accurate answers.

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post #2 of 13 (permalink) Old 06-19-2007, 01:06 AM
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Welcome to the forum.

I think your problem is a sticky IAC (ISC) valve but possibly not the only problem, so I suggest you take that off and clean it with carb cleaner and then see how it idles then.

Disconnecting the wires on the air intake would make the ECU use a 'limp home' value in place of that signal, which would result in a rich mixture, which likely masked the real problem.

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post #3 of 13 (permalink) Old 06-19-2007, 09:27 AM Thread Starter
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Originally Posted by ron1004
Welcome to the forum.

I think your problem is a sticky IAC (ISC) valve but possibly not the only problem, so I suggest you take that off and clean it with carb cleaner and then see how it idles then.
Thank you for your answer. I will do just that.

Could you possibly show a picture of what the IAC looks like and where exactly I can find it? I googled some pictures and the only thing I could find on my car that kinda looks like the IAC valve, is a piece that's exactly opposite to what I think is the throttle valve. It's right next to the opening of the metal part of the air intake (the one that connects to the tube that comes from the air filter).

Quote:
Originally Posted by ron1004
Disconnecting the wires on the air intake would make the ECU use a 'limp home' value in place of that signal, which would result in a rich mixture, which likely masked the real problem.
I imagine both problems combined guarantee a very poor mileage. My car has been doing around 20 mpg and I'm pretty sure it's doing less right now
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post #4 of 13 (permalink) Old 06-19-2007, 07:07 PM
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Try this site for more info, and bear in mind that the IAC is often called ISC.
Global Service Way

Attached to the throttle body is the TPS, which is inline with the buttefly valve shaft, and the ISC which effectively bypasses air around the throttle butterfly valve.
See below picture of the ISC off my car, which may be exactly the same as yours, or similar.

A problem ISC valve will not impact on fuel consumption.
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post #5 of 13 (permalink) Old 06-19-2007, 09:55 PM Thread Starter
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Thank you Ron. This is really helpful.

Right now I'm letting the engine cool down and I'll try cleaning the IAC/ISC with the Carb Cleaner. I just hope I have the right tools.
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post #6 of 13 (permalink) Old 06-20-2007, 12:30 AM
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one other thing i would check is the air filter tubes make sure there is no rips in it
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post #7 of 13 (permalink) Old 06-20-2007, 10:35 AM Thread Starter
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^ The tubes had rips, but those were glued together nicely some time ago. Last night we covered one end and blew hard on the other to see if any air leaked out, but it seemed fine.

The big filter box is kinda loose though. It no longer has the screws that hold it tightly closed, but it's been like that for a long time, way before the engine began stuttering.

.......................

So last night we cleaned the IAC. Surely enough, it was full of grease and valve felt sticky. After cleaning, the valve was loose again and if you moved it, it would spring back into place.

After putting everything back together, the engine still stutters very heavily, but it's no longer difficult turning it on (I had to rev it otherwise it would not turn on or it would shut off almost inmediately). Also, when idle, the engine seems to rev itself to keep it from shutting down. This morning when I drove, it only shut down twice, 3 times at most (compared to it shutting down at every slowdown / stop / traffic light / intersection / etc).

Another thing I forgot to mention, is that the brakes get really hard everytime I take my foot off the throttle, making braking very difficult. It only happens at low rpm's.

Now that the IAC is cleaned, and the engine still stuttering but not shutting down as often (that is quite an improvement for me), I am suspecting there is something wrong with the spark plugs. I checked the connectors last night, and one of them had a lot of oil (remember I mentioned I think I poured too much oil into the engine? ). I cleaned it with Carb Cleaner, but I didn't have the tools to take out the spark plugs in order to clean the ends that produce the spark. I might buy all 4 spark plugs just in case.

The engine stutters a bit less with the A/C on. With the A/C off, it is more likely to shut down and you can hear weird sounds on the engine, like it's not making proper combustion or like when water goes into the spark plugs.

Thank you all for your help. I will keep you updated as soon as I make some progress (or try anything). Hopefuly this thread will help anyone else (a newbie like me) who has a similar problem in the future.
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post #8 of 13 (permalink) Old 06-20-2007, 02:57 PM
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Quote:
Originally Posted by joebob
^ The tubes had rips, but those were glued together nicely some time ago. Last night we covered one end and blew hard on the other to see if any air leaked out, but it seemed fine.

The big filter box is kinda loose though. It no longer has the screws that hold it tightly closed, but it's been like that for a long time, way before the engine began stuttering.

.......................

So last night we cleaned the IAC. Surely enough, it was full of grease and valve felt sticky. After cleaning, the valve was loose again and if you moved it, it would spring back into place.

After putting everything back together, the engine still stutters very heavily, but it's no longer difficult turning it on (I had to rev it otherwise it would not turn on or it would shut off almost inmediately). Also, when idle, the engine seems to rev itself to keep it from shutting down. This morning when I drove, it only shut down twice, 3 times at most (compared to it shutting down at every slowdown / stop / traffic light / intersection / etc).

Another thing I forgot to mention, is that the brakes get really hard everytime I take my foot off the throttle, making braking very difficult. It only happens at low rpm's.

Now that the IAC is cleaned, and the engine still stuttering but not shutting down as often (that is quite an improvement for me), I am suspecting there is something wrong with the spark plugs. I checked the connectors last night, and one of them had a lot of oil (remember I mentioned I think I poured too much oil into the engine? ). I cleaned it with Carb Cleaner, but I didn't have the tools to take out the spark plugs in order to clean the ends that produce the spark. I might buy all 4 spark plugs just in case.

The engine stutters a bit less with the A/C on. With the A/C off, it is more likely to shut down and you can hear weird sounds on the engine, like it's not making proper combustion or like when water goes into the spark plugs.

Thank you all for your help. I will keep you updated as soon as I make some progress (or try anything). Hopefuly this thread will help anyone else (a newbie like me) who has a similar problem in the future.
I would put a fuel filter and a set of plugs in it sounds like it needs it any way unless u already done it. P. S. sorry to here about the mugging next time just shoot them
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post #9 of 13 (permalink) Old 06-20-2007, 06:58 PM
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the engine will stutter like crazy if your plugs are fouled
ok this has hapened to before with water and with oil.


Stuff to buy and make sure you have sometime set aside there is a 3 1/2 waiting period for cooling of the engine.

If u dont have them it would be wise to get them:

Spark plug socket
flashlight
socket wrench 10mm is needed.
screwdriver
thin lint free rags if possible if not paper towels is fine
flathead with a long shaft

Optional:
Spark plug wires and coil over packs (only if youe CEL (check engine light) is on and you are getting misfire codes)

Valve cover gasket( if never replaced)


Ok..... here are some tips

1) I would go to any parts store and but a spark plug socket wrench. Make sure it has the little rubber washer inside the socket. It prevent dameging the spark plug

2) I would buy a good grade of spark plugs since the better the spark
plugs the better the idle and the better the acceleration, and they last longer also. Bosch platinum is good but if you wanto to be on the OEM side get the ngk spark plugs.

3) This is important!!!!!!..... WAIT atleast and no less than 3 1/2 hours before you remove the spark plugs!!!!! If you do not u will cause irreversible damage to your cylinder block, and you will have to get the engine replaced... Even if you drove less than a mile the wait period is still the same. The engine block heats up extremely quick.

4) once the engine is cool, Here is a picture of the Engine bay:




see where it says "KIA DOHC" remove that cover. It's about 8 screws.
After the cover has been removed, you'll see two coil over packs(it looks like it has wax on top of it.) and two sparkplug wires. Those are where the spark plugs arer located underneath those.

Remove the first spark plug wire (just pull up), start with the farthest left first, and remove the spark plug wires and coil over packs, REMEMBER THE CORRECT ORDER... if you connect the coil over to the wrong wire it'll stutter just as bad! in case you forget.



I would leave the spark plugs IN until as much oil as posible is removed. U can use a screwedriver with a long shaft or something long thin and solid. Clean out that chamber, and be GENTLE ( you don't want to damage the spark plug while in the chamer) and take a rag or paper towel and something long and thing, maybe a flathead screwdriver or something and soak up the oil by wiping it with the towel around the spark plug. Make sure to get any oil on the wires also and to make sure nothing is left in the chamber i.e. a peice of cloth or paper towel.

go for the the coil over pack adjacent and do the same as before. Inspect each chamber with a light to make sure all the oil is soaked up.

5) Take the spark plug socket wrench (heres the one i use)




Insert it into the chamber and rotate and push down t'il u get a snug fit. Lefty loosie righty tighty....... and the spark plug will come out. Compare the old spark plugs to the new ones and place the new spark plug into the spark plug socket wrench until snug and place into the chamber.
please do NOT overtighten them damage thread are no good! Tighten the spark plug until it feels snug then go a 1/3 of an inch more.
do the same for all the spark plugs, refer to the pics i have above to replace the spark plug wire and coils in the right order.



A side note would be to check the valve gasket cover for any leaks of oil. Because a bad valve cover gasket will allow oil to enter the chamber again and also will leak oil onto the rest of the engine. While changing the spark plugs it would be a good ifea to change this as well. here's a pic it's # 9 (valve cover gasket- rubber). please get the exact same one. from the auto store. this pic is from Kia Car Parts & Accessories Online... it's wat the dealership uses to look up parts.



removing that is just removing all the the screws that hold the cylinder head. It's about 12 -14screws i think. Do NOT get any WATER underneath the cylinder head, or on the cylinder head. peel out the old gasket and fit in the new one. the new one should be really soft and rubbery. Tighten all the screws down replace the spark plug wires and coils and the spark plug cover and your done. hope fully this helps.
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post #10 of 13 (permalink) Old 06-20-2007, 10:54 PM
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WOW! Great post Spade.

Where are the diagnostic codes, Go to Autozone and have them pull the error codes from the ECU. I would suspect some codes like P0171 (engine too lean Bank1)

I would look at the history of the car. Since you drive it you will know best what has and has not happened to the car.

To Quote you....
(The tubes had rips, but those were glued together nicely some time ago.) and (The big filter box is kinda loose though. It no longer has the screws that hold it tightly closed, but it's been like that for a long time, way before the engine began stuttering.)

I would check the MAF sensor. It has most likely gotten some dust on it and does not work 100% (The KIA manual says to clean with Brake Cleaner) Just remove the security TORX screws holding it in and spray with cleaner. Let dry thoroughly. install and check for codes again.

If it does work now...seal the air cleaner box and hose with whatever you can so not to allow dust to settle on the MAF sensor again.

I would also check the spark plugs themselves. Many times the manufacturer sets the gap of the plug and it is not the optimal setting for the KIA. I had mine set at .44 for a long time and finally found the spec that says .32 to .35. WOW what a difference that made.

I love my little KIA too. I rarely do any maintenance except change the oil. But when something goes wrong, I usually have to fix it myself. I have not had too much luck in getting the dealer to fix the problem. Usually after a few days of head scratching they try to sell me a computer. I wish they would stop trying to sell me a new Computer or a replacement car. I have had this one since it had 17 miles on it and don't plan on getting it replaced.

1999 Sephia 125K. Bought new. Original almost everything. Redline RPM everyday.
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