Edmunds Answers



  • karjunkie 01/02/10 5:54 pm PST

    Your symptoms are usually related to a fuel delivery problem. It can be several things so the best course of action so you don't waste money is to go get a free scan at your local auto parts store. It can be a weak fuel pump, clogged fuel injector, dirty MAF sensor or a leaking fuel pressure regulator in most cases. How did the spark plugs look when you took them out? Once you get those codes come back and we'll try and help.

  • cardocnate 06/17/10 1:07 pm PST

    The first thing you should do is change your fuel filter. I had a similar problem with my ZX5 and this was the issue as it had not been changed since coming off the line. If that has recently been done then move on to the next step.
    You might want to check out your Throttle Body Position Sensor (TPS). It sounds like you have a voltage leak somewhere through this circuit. These can generally be checked out with a digital multi-meter and some patience. Alternatively it could be the Idle Air Valve (IAV), usually close to the throttle body-looks like a silver or black tube with an electrical prong on it, giving you some intermittent problems. Sometimes taking this off (be sure to get a new gasket if you do) and spraying some good throttle body cleaner into these can get them to working again, but if that fails you will need a replacement. Sometimes these things won't even throw a code, happened in my 2000 ZX2 zetec motor-which is a similar, able it not identical, setup to the 02 Zetec, so it can be a pain manually diagnosing.

    Personally, I would start with the TPS and check the voltage readings throughout the range. Essentially this thing acts as a variable resistor depending on how wide the throttle is open. This then tells the PCM how much fuel air mix is entering the engine and other important variable such as timing shifting etc. also depend on this information. You can usually get specs from AutoZone . The voltage should increase smoothly as the throttle butterfly is opened. Some are between 0-5 V while others are between 0-12 V.

    If it's your IAV then you will probably have a sensation of constantly varying idle, almost as if the rpm needle is bouncing up and down between ~450-750 rpm. This is generally pretty obvious, but sometimes it's an intermittent problem so you won't always experience it. I have seen some really oil/debris clogged ones that will only start acting up once the engine warms up, probably b/c it starts to heat sink the electrical connections.



Top Ford Focus Experts View More

Rank Leader Points
1. MrShift@Edmunds 365
2. karjunkie 235
3. Stever@Edmunds 185
4. zaken1 175
5. texases 105
6. tony78 95
7. knowledgepower 80