asked by on

2000 Ford Focus ZX3 DOHC. Got the A/C system fixed by a local mechanic months ago. Told me that he changed out the compressor & condenser. After the car was brought back, it began to have idling issues causing it to sputter & occasionally shut off whenever the A/C was on. I was told that the IACV was probably the culprit, so I changed it out w/ an aftermarket one from Autozone. After doing so, a new problem arose: I now get high RPMs upon start-up. I assumed it was the car warming up to the cold weather, but whenever I'm driving, it still occasionally revs up to 2.5k RPMs as if it needs to shift up. In addition to this, the RPMs sometimes remain the same even when I take my foot off of the gas, & car continues to speed up. If I start braking, the car fights back & jerks. Upon a complete stop, jerking continues until the RPM finally plummets to <1k. If it helps to mention, the car sat undriven for over a year before I got it from its previous owner. Thanks for your time.

My car has 77000 miles.
My car has an automatic transmission.

The first thing to check for in any drivability problem is air leaks. Any air that gets into the engine without being measured will lean out the system and cause problems. Look at all the rubber hoses and boots under the hood to be sure they are well connected and in good condition. If the check engine light is not on, it probably should be. Turn the key on without starting the engine, the CEL should be on. This is a bulb check feature. If the stays on after starting it means there are trouble codes stored that can help in the diagnosis. These can be read by a technician with the appropriate scan tool. The other likely source of trouble is the throttle body. It’s common for there to be a buildup of carbon and varnish on the sides of the throttle body that can in interfere with movement when the throttle is closed or nearly closed. This can usually be cleaned out with a good solvent. To have this done for you at your convenience, you can contact YourMechanic, they can send a technician to your home or office to check out your rough idling Focus and let you know what can be done for it.

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

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: when i start my rav4(1997) the rpm goes high for about 5 min althought that wasnt occur before a period of time ,, what might be t

Hello, thank you for writing in. There are several causes for high idle after starting. The first thing to consider (although it has its limits), is that the engine does need more fuel when cold. This is why all cars...

Q: Why Does an Engine Idle Fast or Slow?

Several factors can cause a fast or slow engine idle. Running the air conditioning or defroster will speed up the idle speed of the engine. Components that impact the engine idle speed include the idle air control motor valve, air...

Q: Driver side window started making a loud grinding sound when rolled down! Wondering what it could be? Motor? Switch?

Hello there. It is possible that your window has become loose and is not entirely on the 'track' that raises and lowers the window. This is typically what causes the grinding noise. It's also possible the window motor is damaged...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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...