Engine Performance problem
2004 Kia Rio 4 cyl Two Wheel Drive Automatic 89000 miles
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.
have the same problem?
Monday, July 27th, 2009 AT 4:10 AM