Question:  2002 Chevy Cavalier mileage: 70,000. My car's idle is supposed to be 900 rpm. Instead it idles around 1500 rpm. Also, it is a manual transmission and when I shift around 4000 or higher, the engine rpm remains high instead of going lower during the shift. I have replaced the IAC. I also have access to a Snap-On scanner. No codes are present and everything looks good. The scanner has the ability to vary the idle, which it does, but the idle is exactly twice as much as the scanner is programming it to do. I have checked the wire connections between the IAC and the computer and they are good. I have also checked the TPS with the scanner and the voltage and throttle position is accurate. At this point, I am leaning towards a computer. Thanks for any advice. 

Answer:   This is a difficult problem to detect because the computer can not sense a malfunction, the vehicles computer system thinks everything is ok. In reality what is happening is the electrical component inside the MAF sensor becomes contaminated by air impurities. These containments imbed themselves to the electrical component that senses the air flow causing the sensor to be slightly off, but not enough to trigger the MIL (malfunction indicator lamp). Replace the MAF sensor with a new. NOTE: (Mass Air Flow MAF sensor or Air Intake Sensor AIS, depending on manufacturer. It does the same thing only with different names).

Question:  2003 Chevrolet 1500 Truck Mileage: 82,000. My truck is in the shop now and the mechanics are stumped  The truck was idling at a high rpm when you start it up and as you drive, it would be ok and then rev up. It would stall at a stop. I would have to press hard on the brake to stop and it would rev and push my foot. Well they changed my EGR valve, a complete tune up; they said some sensors were out. So they fixed that and the truck still does it. They put in a new computer, still doing it. They checked the mass air sensor, still doing it. They said they just don't know; they are looking into maybe a faulty wire. I am getting so stressed and so are they. 

Answer:   If the computer has not been scanned for fault codes, this should be done first.  There may be a faulty idle air control motor and/or oxygen sensors.

Question: 2004 Toyota Camry mileage: 34,000. Upon cold start-up, my new Camry jumps to approximately 2,000 RPM for about 5 seconds and then the Rpm's drop to about 1,500 Rpm. I fear that this initial jump is too high for cold warm-ups. Is this initial jump typical of the new Camry's? Should it be taken in? It does this every time it is cold started.

Answer: The cold fast idle rpm is controlled by the computer. Its sounds like the IAC control motor is sticking or shorted. Also there may be a faulty idle air control motor and/or oxygen sensors.

Question:  2003 Honda Accord, mileage: 46,000. I have a same problem as listed in another posting, on cold start the car goes into fast idle mode and after a minute the idle starts to jump between 1,500 rpm and 1,800 rpm. I've been trying to fix this for a year. I've replaced the O2 sensor and PVC valve as you told the other poster to do. I've also replaced the Air Temp sensor (TA), Water Temp sensor (TW). I've stumped the dealership, as they find nothing wrong. I even replaced the fast idle valve and EACV! The engine has been tuned and I have no clue what else to do? After the engine is warm, everything is great and runs really well and car is like new after constantly doing the service on time.

Answer:   The data stream from the engine to the computer should be read to determine the values of the various sensors on the car. In addition, check to see if the ground wires are properly attached and making good connections.

Question: 2002 Ford Focus, miles: 98,000. I have had my car to three different mechanics in the last month.  No one can fix it.  It idles high.   It will get to 58 mph with out ever putting my foot on the gas pedal.  We have had the throttle sensor and the idle air control sensor changed.  The computer showed that the I.A.C.sensor was bad.  Please help.

Answer:  Replace the Mass Air Flow Sensor as it may be failing.

Question: 2002 Dodge 1500 truck mileage: 65,400.  It started to idle at 2000 rpm's after we steam cleaned the engine and we just did an oil change. Any suggestions?

Answer: The moisture in the wire connections changes the resistance fed to the computer.  Try disassembling the wire connections and drying them.

Question: 2004 Ford F-350 mileage: 59,000.  After filling the tank recently the engine speed became erratic: it would race while driving (tach at 1800 forcing me to keep my foot on the brake in a 25 mph zone); when braking for a turn it would vary wildly between a couple hundred and 1500 rpm; if breaking quickly rpm would fall to under 400, would sputter and stall unless I would two-foot.  It continued to do this intermittently, sometimes stalling while cornering.  I took it to the dealer for its 60,000 mile scheduled maintenance; they found no problem except a possibly partially clogged fuel injector.  I used some OTC fuel injector cleaning stuff to no avail.  Took it to a very good independent mechanic.  He spent three days checking sensors, motors, valves, computer, draining and replacing the fuel.  Everything independently checked out A-OK.  He's mystified.  What do I do now?

Answer: Read the data stream at the computer.  Check for vacuum leaks and check the operation of the idle speed motor.

Question: 2003 BMW 740il mileage: 56,000. I really, really hope you can answer this one. Let me know if you need more details or if it is something that doesn't have a clear answer. My carl periodically increases its idle while at the same time; the antilock brake light comes on. This behavior occurs at 10 or 15-minute intervals at times, or many times the car just idles fast with the ABS light on. Idle is as fast as 20,000 rpms. It has a new alternator and a new battery. I did notice there was no blow-by smoke seen when looking inside the breather with the motor running.

Answer:   This is a difficult problem to detect because the computer can not sense a malfunction, the vehicles computer system thinks everything is ok. In reality what is happening is the electrical component inside the MAF sensor becomes contaminated by air impurities. These containments imbed themselves to the electrical component that senses the air flow causing the sensor to be slightly off, but not enough to trigger the MIL (malfunction indicator lamp). Replace the MAF sensor with a new. NOTE: (Mass Air Flow MAF sensor or Air Intake Sensor AIS, depending on manufacturer. It does the same thing only with different names).

Question:  2003 Chevrolet Lumina mileage: 70,000.  My mom’s car sometimes races and is hard to stop, sometimes it stalls and other times it idles so low it's close to stalling and sometimes it runs fine.  Her mechanic has replaced ($$$) every item he could think of and nothing has helped.  She took it to a Chevy dealer and they did not know what the problem was and wanted to replace the computer.  Well, she knows two other people with 1990 Luminas with the exact same problem.  No one has been able to fix them.  One did have the computer replaced and it did not help.  Any suggestions?

Answer: Replace the idle speed motor, as it may be faulty.  In addition, service the fuel injection system.  Clean the carbon deposits from the throttle bore and idle passages.

Question:   2003 Ford Focus mileage: 62,000.   Hi Guys, there are two symptoms, possibly related. Both problems are intermittent, but occur approx. 70% of the time. 1. High idle at around 2200 RPM, only when fully warmed up, especially when stopping at a traffic light after highway driving.  It will stay at 2200, and then gradually reduce to around 1500 RPM before returning to normal.   This process usually takes 30 or more seconds, sometimes over a minute.  2. When in "high idle mode", the engine will cut out at full throttle.  I noticed this one-day when the high idle made, me made and I tried to make a jackrabbit start when a light turned green!  Through each gear (5 spd), it will drown out at full throttle, and I have noticed that it smokes (gray) when I hold the pedal down during this cutout time, and smells really fowl-- like a combo of a catalytic converter and raw gas.  Any ideas?  I have been putting this off for a few months now, but it is getting worse.  I drive about 2500 miles per month and feel like I may be stranded soon!

Answer:    Your car is equipped with a computer controlled engine management system.  An independent auto service center can scan your computer for fault or error codes.  The information should pinpoint the malfunctioning components.