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1999 Sephia
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3 Posts
Discussion Starter #1
New poster, thanks in advance folks. 99 Sephia stick with about 130k.

Here's my problem: The car starts and idles perfectly. When I touch the gas pedal the rpm drops and the the car appears to stall, but if I let up the gas it settles back at normal idle. If I feather it gently to get the thing rolling up past about 2000rpm it will leap to life like it should.

It drives almost fine at higher rpm and once warmed up, but cold temperatures and rain make it a bear to leave the house. I say "almost fine" because there's a slight stumble even at steady highway speeds.

I've looked all over the internet for a similar problem and can't find anything.

So far I have:

New plugs and wires x2 times, double checked correct gap.
New coil packs.
New alternator (needed it anyway).
New valve cover gasket (needed it bad).
Seafoam a few times.
Carb cleaned everything I could reach.
New air filter and intake hose (it was cracked).

After the new coil packs, it seemed to get a lot better but not go away completely. This makes me think it's something to do with the ignition or mixture but I'm out of ideas. Any thoughts?
 

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Registered
1999 Sephia
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3 Posts
Discussion Starter #2
Still looking for help on this one please. I went through KGIS and everything checked out according to their algorithm. MAF has good voltage, no misses or CEL. Everything is either new or clean that I can think of, but as the weather gets colder the problem gets worse.

On cold start, the engine has zero throttle response below 3000rpm, then it's fine. Pressing the gas makes the engine stumble a little bit and almost stall. As it warms up the problem gets better but doesn't go away entirely. Even when hot, there's a definite hesitation below 3k that is totally nonexistent above 3k.

Help please???
 

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1985 Subaru Loyale (wagon), 2000 Kia Sephia (sedan), and 1969 Mercury Comet (coupé)
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2,858 Posts
... Carb cleaned everything I could reach.
... Any thoughts?
If you used Carb Cleaner Spray on the MAF, there is a Chance that you ruined it, because as far as I know, the Carb Cleaner fluid is UNSAFE for the MAF, you shoud used MAF cleaner instead.

I Use this one:

~► CRC 05110 Mass Air Flow Sensor Cleaner - 11 Wt Oz. : Amazon.com : Automotive


Also, the Injectors could be Clogged... have you tried with a Complete can of injector cleaner (of Good Quality) on Half gas Tank? ... that will be Concentrated enough to Remove any Gum or Varnish it could have on Fuel System.

Also worth measure the Fuel System's pressure, maybe the Fuel Pump is failing...

Kind Regards.
 

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1. 2001 Kia Sephia 2. 2008 Kia Rio5 3. 1991 Ford F150 4. 1994 Mercedes C220
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19 Posts
May as well replace the fuel filter and see if that helps. Pretty cheap and would be a good place to start
 
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