So I have an 03 Focus ZX-5 with 227k and the 2.0 A/T. I've noticed a few weird things lately. When I start the car up it revs up higher like if I stepped on the accelerator when starting up. The other concern is the car will accelerate on its own after coming to a complete stop. Sometimes when accelerating, the car will continue for a little bit longer, then slow down. I'm not getting any codes from the engine. I've cleaned the throttle body and replaced the throttle position sensor. I even held my foot under the accelerator when starting the car to see if it was a sticky accelerator pedal. Once stopped at a light it revved up to 1500 rpm and turned off, I started it back up and it was fine (the issue has not reoccurred). Anybody have any ideas as to what my next step should be? Any advice would be greatly appreciated and thank you in advance.
M0L0TOV
Update: I disconnected the battery overnight but the issue still persists. It's not as bad as before. When the car cools down. I'm going to check the line for the PCV valve and see if it's collapsing during use.
I thought I had updated it but not. So I disconnected the battery overnight and it seems a little bit better. Next step is to replace the hose for the PCV valve and I'll replace the PCV valve while I'm at it. I've read that if the hose collapses because of age, it can cause the same issues.
Replaced hose and PCV valve, car is running rough now. I think I'm taking it to the mechanic tomorrow.
It's time to replace the IAC (Idle Air Control) Valve.
I'll try to knock that out today and I'll report my findings. Thank you
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Just be sure to check the IAC valve's wiring connector too. The IAC valve needs the signal from the computer to function. Look for any damage or corrosion on that connector and its wiring
So the IAC valve has been replaced and it seems worse. I didn't have enough time to let it warm up after the mechanic but I had to drive with my foot on the brake because it kept accelerating. I'm beyond words. :/
I can't see why a mechanic would release a car to a customer like that. When replacing the IAC valve the battery negative cable should be disconnected so that the learned KAM (Keep Alive Memory) is cleared. Then after the job is done the car should have been started and allowed to idle for about 10-15 minutes to relearn the IAC setting.
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If the idle didn't come down he should have simply disconnected the connector to the IAC valve and made sure the idle came down. If it didn't then he should have looked for a reason that unmetered air was getting into the intake. On the Focus the PCV valve's hose in the back of the engine being deteriorated and sucking air should have been the 1st place he looked.
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You can disconnect the negative battery cable for about 15 minutes to clear the KAM and then reconnect it and let the car idle for another 15 minutes to relearn the IAC settings.
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If that doesn't bring it down then unmetered air is entering the intake and the PCV valve being stuck open or the PCV valve's hose being broken should be checked
This is super insightful, I'll try it out tomorrow or Monday. I know it's silly to ask but how do I check my vacuum tubes for air leaks? Thanks again!
Look for any loose or disconnected vacuum lines.
So I left the battery disconnected for a few days and let the car idle without the a/c on for 20 minutes. I'm at a loss. I tried driving it and especially at lower speeds, I try to brake and the car keeps accelerating. This is in no way safe. Have I missed anything? IAC valve, PCV valve, PCV EVAP hose, throttle position sensor, throttle body cleaned. Whenever I start it up it's at a higher RPM than it used to be, it's like if I started it with my foot on the accelerator. I'm baffled. Or should I throw in the towel and go back to the mechanic? Thanks in advance!