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Discussion Starter #1 (Edited)
I have a 2001 kia sportage, 4cyl, 5spd, with 97000 miles on it. I encountered the following problem: The engine starts fine from cold but the car has problems accelerating properly. It maxes out at ~2500rpm even in standstill. When I decide to push the accelerator all the way the engine does not rev up beyond 2500rpm. When doing that the engine sounds like it is awfully trying but failing to rev any higher. Once I fully release the accelerator, the rpm goes down below idle rpm and the engine turns off. I also noticed an elevated fuel consumption over the last two weeks. What could be the problem?

A little while after I started encountering this problem I got a check engine light with the following error codes:

a) Multiple Misfire
b) Fuel mixture too rich (O2 sensor)

I believe these codes could have been thrown because too much fuel may have gotten into the cylinders when pressing down the accelerator and the rpm being stuck at 2500rpm.

Here is what I tried so far:
1) I start the engine, let it idle for 5 minutes, push the accelerator without any gear engaged and am able to rev up to 3500/4000 rpm. When pressing the accelerator all the way the engine again doesn’t rev up any further, rpm rather decreases from 3500/4000 down to 3000 and once I fully release the accelerator the engine turns off.
2) If I drive my car for about 10 minutes acceleration seems to get better and I am able to get up to around 3000rpm. However the “full accelerator -> release accelerator -> engine off” problem persists. Acceleration in 1st gear seems fine but I am not rev-ing beyond 2000rpm.
This might not be related but there seems to be some vacuum buildup in the fuel tank as I hear a hissing noise when unscrewing the fuel cap. Once in a while I also hear some rattling noise from near where the fuel pump is located (near where the gas cap / tank is located).
3) I searched dozens of forums and read about stalling/ low rpm problems encountered by various other owners but nothing that completely fit what I am encountering. The following seem to have been possible causes for engine stalling / no power / low maximum rpm: fuel pump, ECM relay, exhaust cat, secondary cat, timingbelt, EGR valve and O2 sensors.

In sight of this multitude of possible causes is there anything I can cross off / check easily? Is there anything I am missing and should consider?

Any help is very much appreciated.

Thanks,
Mark
 

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Caribou, Otter, Buffalo
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I would cross off the easiest first, remove the upstream O2 sensor and run the engine(open bung), if it runs up with no hesitation you have a restricted exhaust.... Philip
 

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I have a 2001 kia sportage, 4cyl, 5spd, with 97000 miles on it. I encountered the following problem:

...

In sight of this multitude of possible causes is there anything I can cross off / check easily? Is there anything I am missing and should consider?

Any help is very much appreciated.

Thanks,
Mark
+1 on restricted exhaust / failed pre-Cat. converter directly below the exhaust manifold,

Also check & clean ground points on the Sporty: Battery terminals / cable ends, battery tray ground point <-> engine ground strap: check the connectors on the engine ground strap, if connectors/wiring is "green" or corroded, replace w/ a new ground strap.

If a restricted exhaust/failed pre-Cat.,

you will need to either pull the secondary (Main) Cat converter, and/or disconnect at the back of the Main Cat. and force compressed air through the secondary converter, to blow out the accumulated ceramic material stuck in the secondary cat. from the failed pre-Cat., (clean out the material in the secondary Cat. if the pre-Cat. failed)

would also consider checking the ignition components: coil packs, HT Leads (spark plug wires), spark plugs, power lead from the back engine block -> to the coil packs: overheat due to restricted exhaust may also impact ignition components / reduce the life of same ..

would also consider checking static timing / timing belt as a sanity check / maintenance item: improper timing will affect ECM operation - and cause excess fuel consumption, reducing pre-Cat. efficiency & life,

*if the fuel filter is original to the vehicle, it's due for a new one.

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would start w/ the easiest though, confirm the pre-Cat. is good or bad, and clean up ground points to ensure good power to the vehicle.

Regards,
GottaCruise
 

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GottaCruise

Glad you are here to follow up and spoon feed.....

I tend to provide small single steps.. Thanks... Philip
 

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Discussion Starter #5
Thank you both for your support. I tried removing the upstream o2 sensor from its socket but without success. It seems to be very tightly screwed in or is just too rusted. Instead I disconnected the electrical wires from the o2 sensor (which I assume lead to the board computer) but this did not seem to change much for me ... I tried reving the engine up in standstill and it only rev'ed up to 3500. Is this an indicator of anything or would I have to physically remove the o2 sensor to figure out if the exhaust is restricted or the pre-cat failed? Could I just feed a certain DC voltage to the board compute, which should indicate 'inject high' or 'inject low' amounts of fuel?

To GottaCruise: Thanks a lot for the detailed debug advice :)

I checked the battery terminals and ground contacts and they seem to be fine. I still have to check the fuel filter and may have to pull the main cat and blow it out just in case (since I couldn't verify it pulling the o2 sensor)... this also depends on how work intensive pulling the cat will be. Can you give me a ballpark estimate on how long it should take or instructions on how to 'pull' the cat?

Something that may or may not have to do with my current problem: Last October I changed the head gasket and I just realized that I did not tighten it far enough... I tightened it to spec on Sunday. Could that have made things worse in cold conditions? It didn't seem to change much after I tightened the gasket on Sunday.

Thanks
-Mark
 

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1999 Sportage A/T 4WD
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You should check the spark plug wires resistance, and in case replace them; although, if they are bad, your Sportage should idle roughly.
 

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You cannot check for exhaust restriction without physically giving the pressure an alternate escape.... the engine has to breath to run....

DO NOT start playing with the electronics, you may do more harm than good.... especially if you cross or miss-connect circuits....

I would suggest, if you are not equip or capable, that you seek professional assistance... Philip
 

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Thank you both for your support. I tried removing the upstream o2 sensor from its socket but without success. It seems to be very tightly screwed in or is just too rusted. Instead I disconnected the electrical wires from the o2 sensor (which I assume lead to the board computer) but this did not seem to change much for me ... I tried reving the engine up in standstill and it only rev'ed up to 3500. Is this an indicator of anything or would I have to physically remove the o2 sensor to figure out if the exhaust is restricted or the pre-cat failed? Could I just feed a certain DC voltage to the board compute, which should indicate 'inject high' or 'inject low' amounts of fuel?

To GottaCruise: Thanks a lot for the detailed debug advice :)

I checked the battery terminals and ground contacts and they seem to be fine. I still have to check the fuel filter and may have to pull the main cat and blow it out just in case (since I couldn't verify it pulling the o2 sensor)... this also depends on how work intensive pulling the cat will be. Can you give me a ballpark estimate on how long it should take or instructions on how to 'pull' the cat?

Something that may or may not have to do with my current problem: Last October I changed the head gasket and I just realized that I did not tighten it far enough... I tightened it to spec on Sunday. Could that have made things worse in cold conditions? It didn't seem to change much after I tightened the gasket on Sunday.

Thanks
-Mark
Hi Mark,

To pull the pre-Cat, remove the exhaust manifold heat shield, use an extension bar w/ socket to remove the nuts securing the pre-Cat to the bottom of the exhaust manifold (loosen only / do not fully remove if taking the pre-Cat off!),

loosen the bolt securing the mid-pipe to the side of the motor, -do not fully remove yet-,

and loosen -> remove the bolts securing the mid-pipe to the front of the main Cat.,

and from the top, finish removing the bolts securing the pre-Cat to the exhaust manifold,

*from underneath the vehicle, remove the bolt securing the mid-pipe to the side of the motor -> drop the pre-Cat and mid-pipe assembly down -> until it clears from underneath the vehicle.

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If the mid-pipe does not have a bracket securing it to the side of the motor, or if the Main cat does not have a bolted flange (aftermarket/welded in), then you will have to further drop the exhaust system to gain enough clearance to (separate) the pre-Cat from the exhaust manifold...

Then run the test to see if the engine is breathing with the pre-Cat dropped away from the exhaust manifold.

Plan B / alternate method to inspect pre-Cat.: disconnect the pre-Cat from the top of the exhaust manifold, then (remove) the exhaust manifold from the engine, you can then inspect the top of the pre-Cat. ceramic honeycomb chamber / run the engine test to see if it revs. normally, may be easier to do this method if exhaust system won't cooperate.

**When testing, would recommend having the upper O2 sensor hooked up / wired out of the way - running without the sensor hooked up is just going to throw codes from the ECM ...

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If you find the pre-Cat is bad, suspect the upper O2 sensor (in the exhaust manifold) is "welded" in, due to overheat... Provision to remove the exhaust manifold to have an exhaust shop torch out the sensor, or replace w/ a new exhaust manifold & new O2 sensor.. My experience was it was cheaper to replace the exhaust manifold, vs. the labor hrs./$$$ the shop quoted to remove the sensor.

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re: head gasket, anything's possible, and you know your vehicle better than I do -

but I would still confirm the engine can breathe ok, by eliminating restricted (Intake) or (Exhaust) as the cause of the issue first.

Please keep us posted on your progress, shout back if we can help.

Regards,
GottaCruise
 
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