Q: Rpms won't drop.

asked by on

I recently had an aftermarket header installed along with a high flow cat. I had to replace the o2 sensor since the original was seized in the exhaust manifold. I drove about a week without the upstream o2 sensor installed and the same day I got it put in the rpms won't drop when shifting, almost all the time, occasionally they drop like normal, and just today I noticed an occasional surging idle upon startup. I've also noticed I'm getting very poor fuel mileage. When my original clutch was going out, the fuel mileage was still pretty good. Could it be the clutch? Iac? Was driving without the o2 sensor for that long capable of damaging anything? Is it safe to drive until I can get the issue addressed?

My car has 158000 miles. Current clutch and flywheel have about 10K miles. My car has a manual transmission.

It is possible you have a large vacuum leak or the idle air control valve is stuck in a position best suited for colder weather. A vacuum leak will allow unmetered air into the engine causing the computer will add fuel to compensate for the lean condition. If the idle air control valve is stuck open it can cause a similar situation. Consider hiring an experienced technician like one from YourMechanic who can come out and take a closer look at the high engine speed concern and offer a more personal diagnosis.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Rpms won't drop.

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: My clutch pedal is extremely "light" and gears won't go in.

There are a few possibilities; you either have a problem with the hydraulics, a mechanical problem with the clutch, or a transmission fluid leak. Hydraulics: When you push down the clutch pedal, the clutch master cylinder (CMC) uses...

Q: Q: Engine idle fluctuates

You may have a dirty or failing idle air control valve. The idle air control valve reads the air intake as it is mixed with fuel prior to being injected into the engine at low speeds and at idle. Since...

Q: Will a faulty Knock Sensor cause my car to shut off while driving?

Less than 1 hour is required to replace the knock sensor (Hyundai OEM part number: 39250-2B000) on your particular engine. The dealer (OEM) knock sensor, which is the preferred part, costs around $50. A knock sensor, even if faulty, can...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...
What are the Car Pool Rules in Hawaii?
Hawaii is widely regarded as a land of vacation and relaxation, and as such, its scenic roads and routes are far better known than the state’s freeways. But, as with all...