2004 Kia Rio Is This Problem Indicitave of a Bad MAF?

Tiny
COACH STEVE
  • MEMBER
  • 2004 KIA RIO
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 89,000 MILES
Greetings Gurus!
I'll get right to the point, if I may.
I have a wicked acceleration problem after the car reaches operating temperature. Sorry for the length of this post but I wanted to give you as much ammo as I could to help you help me. It has not thrown any codes nor does it have any stored codes.
When the car is cold and has not been driven for the day or overnight, it performs as it should.
The HP is acceptable for the size of the engine and the acceleration is adequate as long as the A/C is off. Engaging the A/C drops the RPM's significantly but with the engine cold, you can easily compensate for the loss in power by giving it more pedal. The car takes the normal amount of time to reach operating temp and when it does, it gives every indication that the thermostat is opening and the temp gauge settles in right at half-way and stays there 90% of the time. (Not bad considering the daily highs of at least 110 deg. F the past couple of weeks here in Phoenix) Once or twice the needle has climbed up to the 3/4 mark and both times I was in stop-and-go traffic with the A/C on during the hottest part of the day. Once the engine reaches operating temp the car becomes a Yugo! When attempting to accelerate from a dead stop the car responds the same no matter of the amount of throttle applied until it reaches approx 40 MPH. When you try to take off, the car moves at about walking speed and slowly but steadily builds up speed until it reaches the desired speed and you back off the throttle. Once it reaches the desired speed, it runs fine and doesn't hiccup or lose speed. During the acceleration process, there is no indication of it missing or starving for fuel it just doesn't want to go while under load - and if the A/C is on when you attempt to take off from a dead stop, the process takes even longer. When it is exhibiting this problem and it is not wanting to go, I can put the car in neutral and rev the Hell out of it no problem. But when it's under load after reaching operating temp, it just does not want to go. To add perspective to the amount of acceleration I'm experiencing as well as the amount of time it takes to go from a dead stop to say, 45 MPH, I have added the following stats which I compiled using my handy-dandy stopwatch! (I am a coach ya know! LOL!)

The following data was compiled with a cold engine and all data listed was while the A/C was OFF.
Dead stop to 45 MPH: 11.0 seconds (Bwaaahahahaha! Maybe it IS a Yugo!) Not quite WOT but close to it. I backed off before red-lining at each gear change.

The following data was compiled after reaching operating temp and again with the A/C OFF.
0 - 45 MPH @ WOT: 26.2 seconds (GO L'IL RIO GO!)

The car doesn't sputter or stumble nor does it exhibit any sounds or smells you would expect from an overheating engine.
The plugs are 4-5 months new. NGK plugs gapped at exactly.030
The air cleaner is new and I cleaned the TB within the past month.
The gas is from a top-tier station (Chevron)
The oil was changed about a month ago with Mobil 1 Full Synth.

When the A/C is on, I experience 3 additional things:
The power loss is significant (With throttle held at 2500 RPM engaging the A/C drops the RPM's to 2000)
The air is not very cold.
The car idles rough with the A/C on.

So there you have it. To me the obvious culprit has to be whatever controls the air/fuel ratio AFTER the car reaches operating temp. If it was receiving too much of one and not enough of the other, the car would exhibit sputtering or choking or even shutting off but it's not. The performance is consistent which tells me that it is being starved for both fuel and air equally at operating temp and while under load until the car reaches approx. 45 MPH. I pulled each of the plugs to see if there might be any kind of sign or evidence there and the plugs were clean and firing normally without any deposit, soot or signs of misfiring.
The car does not emit any smoke whatsoever whether hot or cold. Both fans are engaging at the correct times. When it is having it's problem with acceleration, the idle does not seem to be affected. It idles the same whether hot or cold. When at idle (hot or cold) the throttle is equally responsive when in neutral or park - no hesitation. The engine appears to be idling at around 700-725 as best as I can tell.
If this is indeed indicative of a failed/failing MAF shouldn't I be getting codes left and right?

Thanks in advance for any suggestions you can throw my way. I'm completely stumped on this one.

Coach
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Monday, July 27th, 2009 AT 4:10 AM

7 Replies

Tiny
MHPAUTOS
  • EXPERT
Hi there,

Thank you for the donation,

As you have suggested if the MAF is out or range it will give a code, so with this in mind I would try and get some live data reading re ignition timing and TPI throttle percentages, also have you considered that this may actually be a hot transmission issue? Have you had the trans tested?

Mark (mhpautos)
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Monday, July 27th, 2009 AT 4:23 AM
Tiny
COACH STEVE
  • MEMBER
Hi Mark, thanks for the prompt reply!
Regarding the live data. Forgive my ignorance but how would I go about that other than taking it to a shop equipped with a computer?
As far as a hot trans issue, I hadn't even thought about that. Could you elaborate on this please. Indications, likely causes, t-shooting I can do to verify/rule-out this possibility. If it is a hot trans issue, is it possible that it could be something as simple as the fluid being low or needing to be changed?
Thanks again!

Coach Steve
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Monday, July 27th, 2009 AT 4:30 AM
Tiny
MHPAUTOS
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Hi there,

To get live engine data you will a suitable scanned plugged in, As for a trans issue, check oil level & condition, you want it bright red and not frothy either, as for other checks this is really the realm of the transmission specialist as there will be some tests with line pressure gages that can be done.

Mark (mhpautos)
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Monday, July 27th, 2009 AT 4:40 AM
Tiny
COACH STEVE
  • MEMBER
I assume the first sentence in your reply should have read as follows. "To get live engine data you will need a suitable scanner plugged in."
That being the case, I will indeed need to take it to a shop. And regarding the trans, it sounds like all I really an do is verify the condition and level of the fluid. Beyond that, I need to employ the assistance of an expert. Transmissions. NO THANK YOU! LOL!
Forgive me for re-asking again in this reply but could you elaborate on the possibility of it being a hot trans issue. Indications, how a hot trans would cause the car to exhibit the behavior it currently is, etc.

Much appreciated!

Coach
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Monday, July 27th, 2009 AT 4:50 AM
Tiny
MHPAUTOS
  • EXPERT
Hi there, yes a suitable scanner will have to be plugged in, sorry I'm in Aust and its been a long day. Now as for the trans or suspected trans issue, low pump pressure could account for this problem, internal leaking of pressure seals as the trans warms up and expands a bit, a failing torque converter could possibly have this effect. Any slipping of the transmission would tend to be more noticeable, you do have one advantage over me, and that you have experienced this first hand, so I am only surmising some possibilities, a transmission test and report should not be very expensive, as if we were able to nail this problem here with a diagnosis, there is very little that you can do with out some rather expensive special tooling, may be start with a basic trans service this you can do your self and this way you can see if there is any excessive muck in the pan which would indicate a possible internal fault.

Mark (mhpautos)
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Monday, July 27th, 2009 AT 5:03 AM
Tiny
COACH STEVE
  • MEMBER
Aussie huh? Good for you mate! I had a close friend many years ago who lived in Perth. He has since passed away God rest his soul but a great mate just the same.
Anyway, I think I'll run it through one of the reputable trans shops later today to have the fluid changed without saying anything and see if they come across anything worth talking about. If they get it put back together and don't say anything, I'll ask a couple of leading questions while scratching my head and looking like a dumb blond and see if their ears perk up. If I don't get even a nibble of interest, I'll know the trans is in good enough shape that even they know there's no money to be made on this one. And if after hitting the trans shop I'm still looking like a deer caught in the headlights over this situation, it's probably time I take it to one of the local shops and get it hooked up to a computer to get some answers we're not going to get any other way.
I'll let you know what happens.
Thank you for your time mate!

G'day!

Steve
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Monday, July 27th, 2009 AT 7:27 AM
Tiny
MHPAUTOS
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G'Day Steve,

Yes that the best way to hit tis one, good luck and let me know how you get on.

Cheers,

Mark (mhpautos)
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Monday, July 27th, 2009 AT 5:18 PM

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