Edmunds Answers

Voted Best Answer

  • avatar karjunkie 11/06/08 10:20 am PST

    Your fuel pressure is good so that is not the problem. Most of the time, erratic Idle is caused by a disturbance in the vacuum system, the engine will continiously try to compensate for the gain and loss of extra air coming into the intake. When you start your car and the engine idles, air bypasses the throttle plate through a couple of holes from the IAC valve. The purpose of the IAC is to let extra air in when the engine is "cold" to help it idle/attain the right A/F ratio; after the engine is at normal operating temperature, your ECU will shut off the IAC valve. The first thing you should look for is any apparent leaks from vacuum hoses, bad seals, improperly tightened mating surfaces on the TB (throttle body), IM (intake manifold), etc. If everything checks out move on to the IAC valve, unbolt the 2 bolts holding it in place then separate it from the IM. Note the 2 holes in it, the one you are mostly concerned with is the hole with the screen on it. Make sure it is not clogged or otherwise obstructed by debris. If it is you can clean it up with carb/intake cleaner. Now, use the rest of the cleaner spray to clean inside the throttle body, especially any the throttle plate. Bolt it back onto the IM and reconnect any hoses or the electrical plug you may have taken off of it.

Answers

  • karjunkie 11/06/08 10:20 am PST

    Your fuel pressure is good so that is not the problem. Most of the time, erratic Idle is caused by a disturbance in the vacuum system, the engine will continiously try to compensate for the gain and loss of extra air coming into the intake. When you start your car and the engine idles, air bypasses the throttle plate through a couple of holes from the IAC valve. The purpose of the IAC is to let extra air in when the engine is "cold" to help it idle/attain the right A/F ratio; after the engine is at normal operating temperature, your ECU will shut off the IAC valve. The first thing you should look for is any apparent leaks from vacuum hoses, bad seals, improperly tightened mating surfaces on the TB (throttle body), IM (intake manifold), etc. If everything checks out move on to the IAC valve, unbolt the 2 bolts holding it in place then separate it from the IM. Note the 2 holes in it, the one you are mostly concerned with is the hole with the screen on it. Make sure it is not clogged or otherwise obstructed by debris. If it is you can clean it up with carb/intake cleaner. Now, use the rest of the cleaner spray to clean inside the throttle body, especially any the throttle plate. Bolt it back onto the IM and reconnect any hoses or the electrical plug you may have taken off of it.

  • wilfreeze 11/15/08 3:32 pm PST

    hi just wanted to thank you for the help on the 92 aerostar w/IAC problem did not have a screen so i replaced the valve and juiced the T/B out real good. seems to done the trick.
    thanks agian


    P.S. when i have more time to work on the van i'll ask your advice.
































Other Questions Needing Answers

ADVERTISEMENT

Top Gasoline Experts View More

Rank Leader Points
1. MrShift@Edmunds 945
2. karjunkie 750
3. texases 490
4. zaken1 485
5. morin2 465
6. Stever@Edmunds 285
7. tony78 180
ADVERTISEMENT