My car will not exceed 2500 RPM in any gear


#1

My car will not exceed 2500 RPM in any gear. In first (or any other gear) gear I can drive up to 2500 RPM and then must shift into 2nd (or the next gear) if I want to go faster, if RPM goes above 2500 the car stops accelerating and the RPM drops to 2000 at which time the car starts to accelerate again. The engine is running at a very high rate when I come to a stop as if the idle is set too high. The car does not lose electrical power when this happens. I have driven the car more than an hour in 5th gear going 45 to 50 mph keeping the RPMs between 2000 & 2500. I can get around town with easily as long as I am staying in the 2000 to 2500 RPM range. This problem started late Saturday night when I was in Phoenix and had to get to the airport to pick up my daughter and then get back home to Prescott, AZ. Since the dealers were all closed on Sunday I just went home at 45-50 miles an hour all the way back to Prescott. It was a long drive but we enjoyed ourselves. The car ran fine except for the RPM problem. Please Advise…Thanks so much.


#2

Since we don’t know the make, model, model year, maintenance history, and odometer mileage of your mystery vehicle, much of the advice that you receive will be guesswork. But…here goes with my first guesses:

If your catalytic converter is clogged, that would cause the engine to be unable to gain speed.
Another possible cause might be a partially-clogged fuel filter or a weak fuel pump.

If you post back with the missing information that I mentioned above, we might be able to be more helpful.


#3

Whew! Car will not rev over 2500 but u continue to drive it? Is your reasoning such that “it’s not on fire”, so it must be ok to drive it?


#4

As VDC said, we need some basic information to be able to help you…


#5

I appreciate you your input and sorry for lacking info. My car is a 2004 Kia Rio Cinco with 82,000 miles, 5 speed with self-adjusting clutch. All regular engine and transmission maintenance has been done on schedule. Everything else with the car is working well. I made sure that I was monitoring the systems as I was trying to figure out just what the symptoms where. If it where a clogged catalytic converter or fuel filter would there not be some sputtering? There has been none, really not even a little bit.


#6

A clogged fuel filter should cause some mis-firing but a clogged converter may not…If the car will coast along normally without any noticeable drag slowing it down (dragging brakes) then a restricted exhaust becomes more likely…have a shop put it up on a lift for a visual inspection and a simple exhaust back-pressure test…If this problem is constant, then any competent mechanic should be able to run it down quickly…


#7

Since I have never experienced anything like this I was feeling pretty unsafe about taking to a mechanic about the problem because they could have told me anything and I would not have been able to spot a good lie. I feel much more confident in engaging a mechanic and asking questions…THANK YOU


#8

To test for exhaust back pressure, the front oxygen sensor is removed (its screwed into the exhaust pipe ahead of the converter, looks like a spark plug) and the exhaust back-pressure measured at that point. 2-4 psi is normal, more than that, something is plugged up…

$100 should more than cover the diagnostics on this and a decent shop might credit this towards the repair if you have them perform the repair. Always ask “Do you guarantee your recommended repair will cure my problem?” Don’t pay for guess-work…


#9

“This problem started late Saturday night when I was in Phoenix and had to get to the airport to pick up my daughter and then get back home to Prescott, AZ”

Since the problem occurred suddenly and has all of the symptoms of a dropped vacuum line, allow me to suggest that you pop the hood and look for any free-hanging disconnected rubber line going toward the throttle body area or from the vacuum booster. You might get lucky.

Ultimately, it may turn out to be something like a dying fuel pump or a collapsed cat converter honeycomb, but it’s worth looking at the vacuum lines. It’s free.


#10

May we assume the check engine light is or was on?


#11

First, a clogged converter will not cause a high idle, so let’s rule that out.
I’ll share my experience with similar symptoms long ago.
The timing belt on my 1975 Civic jumped ahead a tooth.
I guess a combination of being loose and parking in gear twisting the engine backward.
The engine would reach a certain RPM an “gag”.
I didn’t know what RPM because it didn’t have a tachometer.
So you might want to get the valve timing checked at some point.


#12

You’re right about the high idle. I missinterpreted that detail,

If the car has an electronic accelerator that should IMHO be considered as a definite possible cause. I know these were common in '04, but I don;t know if Kia was using them.


#13

U put car is 1st gear, accelerate to 2500 rpm and ? Car will not accelerate past 2500? U say motor does not stumble or hesitate. It hits 2500 and stays there? U push on gas pedal and no change?


#14

I don’t know for sure about an '04 Kia Rio, but many cars have a “limp” mode. This allows the car to be driven after a major fault has been detected by the car’s computer. Limp mode can allow you to safely get off the road and limits the power and rpm of the motor until a repair is made. In limp mode you should have a CEL (check engine light) either on, or flashing. Some cars have a “wrench” symbol that shows the car has a mechanical problem.

Some things that can cause the limp mode to go into effect are; a motor overheating, a transmission overheating, numerous misfires, and so forth. While any mechanic can read some codes, a Kia dealer has more specific diagnostic equipment that can read emission and transmission codes if any are stored in the car’s computer. I’d take the car to a Kia dealer, ASAP.


#15

Because it is so easy, inspect the air filter.


#16

I’m having exactly the same 2500 rpm problem katfur described with an 03 rio cinco. What proved to be wrong with yours? The engine hits 2500 rpm and loses power but does not die. The idle point is high about 1500 when the fault initially happened then it creeped up over time to stay at 2000.

The codes thrown are below. Some of these may be quite old since I never clear them out.
P0420 Catalyst system below Threshold Bank 1
Po128 Coolant Threshold Below Themostat Regulating
P0325 Knock sensor bank 1
P0301 Cylinder 1 Misfire
P0121 Throttle position sensor A Range Performance


#17

Make a note of the codes, clear them, and see what new codes it throws…When is the last time you changed the fuel filter?


#18

Have never changed the fuel filter. Will clear the codes tomorrow.


#19

But I haven’t owned the car very long either. Fuel filter has probably has never been changed. I wouldn’t expect the high idle from the filter though.


#20

P0121 would be the first thing on my checklist…