1996 mercury sable- after driving for a while the car picks up rpm when its shifted into park. it slowly climbs to 3000 rpm- its a real big problem because shifting back to drive with that must rpm...
any ideas of what could be wrong????
2007-07-07 02:53:09 · 3 answers · asked by Anonymous in Cars & Transportation ➔ Maintenance & Repairs
While I like the suggestions above, I'd expand on them a bit.
A bad /sticky EGR valve can give you the same symptoms as a vacuum leak. Don't overlook that as a problem. Do check for vacuum leaks as well. If none are obvious, the most frequently used test is spraying a bit of carb cleaner around the fittings to see if the idle changes. Some use propane, but I don't trust most folks to do that without causing themselves grief.
As for the TPS (throttle position sensor), you'll want to check that before replacing it. It's back on the end of the intake manifold, mounted to the throttle body. Understand, too, that installation of this little beast can *cause* a fast idle. Be sure to scribe before removal and watch how you assemble before you rotate a new one into position when replacing.
At the TPS connector, and measured against ground (and it MUST be the ground on the connector itself, since these voltages will be small), you should get between 0.6 and 1.0V from the TPS with the throttle closed. You should get about 3.6V *higher* than your first reading at full throttle. So if your first reading is 0.8V, you should see at least 4.4V at full throttle open. You should also see a smooth increase in voltage as you slowly open the throttle. (Edit: Found a good link with a pic of the connector for you -- see below -- in fact that site is pretty nice for just about all of the Ford EFI descriptions it provides).
You're right about needing to get this fixed, though. Not only is it a bit unsafe to have to deal with that much fuel just as you engage the tranny, it's hard on the tranny!
Edit:
Ref the post below, a defective IAC will typically cause rough or *low* idle -- even wide open, it should be incapable of generating enough bypass to reach 3000 rpm.
However, I just thought of another possibility -- the BAP (barometric pressure) sensors are able to cause this problem (high, surging idle), too. The connectors on these sensors are known to corrode and will cause trouble.
2007-07-07 04:31:42 · answer #1 · answered by C Anderson 5 · 0⤊ 0⤋
It seems that the IAC (Idle air control) valve is opening up too much. It may be leaking or sticking.
2007-07-07 13:18:25 · answer #2 · answered by Mad Scientist Matt 5 · 0⤊ 0⤋
Check for possible vacuum leaks. If OK then the TPS has failed
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2007-07-07 10:00:04 · answer #3 · answered by Mr. T 7 · 0⤊ 0⤋