Very high idle

30

Asked by May 13, 2015 at 06:32 PM about the 2002 Mercury Grand Marquis

Question type: Maintenance & Repair

Cleaned engine. Blew off, dried
everything, disconnected all wiring
connectors blew dry and reconnected
all wiring, hoses, and removed all
coilplugs blew out dried boots and
applied dielectric lube. Car starts and
runs great, EXCEPT IT IDLES AROUND
2000RPM!. I removed the tps,
disassembled it and it was dry and
functioning. Still high. I disconnected
the plug from the tps, still high and
throttle acts normal?. If I pull the lg.
Tube from the IAC to the intake hose
and plug the tube with my thumb,
normal idle. Put tube back into hose
and disconnect plug to mas and idle
drops to almost stalling then idles
normal. Any and all suggestions would
be great. ALSO NO CODES CAME UP
ON TESTER AND I ALSO REMOVED
THE IAC CLEANED AND
REINSTALLED. THANKS.

6 Answers

73,935

First thing to do is look for a vacuum leak. On a computer controlled engine that's the A#1 cause for a high idle. If this started after you disconnected or replaced the battery there's a procedure that needs to be done when reconnecting the battery. If not done, you can get a high idle. Talk to your local Ford Dealer about this procedure. HTH. -Jim

1 of 1 people found this helpful.
Best Answer Mark helpful
30

Thanks for your email Jim but I already ran the sequence in the owners manual when you replace or disconnect the battery. I followed and checked every vacuum hose and connectors, all seem OK. I think it is the IAC valve. I had a problem with the EGR system due to pack rats chewing the vacuum hoses a few yes. Ago. All lines were replaced along with a few control valves. This is the first problem ( with the exception of a new fuel pump last year) since all the mentioned repairs to vac lines etc for the egr. Thanks again. Fatboy2002

1 of 1 people found this helpful.
73,935

You're welcome. Glad to help. Thank you for the best answer click as well. I agree about the IAC. Since you've covered all the other bases that's where I'd go next. -Jim

30

I ordered one this afternoon. I should have it by 2:00pm tomorrow, AZ time. I let you know what the outcome is after its installed. Also when I took the car for a drive about a hour ago, I put 25 miles on it, it was hard to up shift without really getting on it. As I turned down my street it was doing 35-45mph without touching the gas pedal! What a ride!!!! Thanks again Phatboy2002.

1 of 1 people found this helpful.
73,935

You're welcome. Yes, let us know how you make out. As always, glad to help. -Jim

Hello, I am having the same problem with my car. The Idle is high and it won't come down. I just bought it and the battery was replaced about a year ago. It appears as though it has had this problem for a while. I was wondering, what is the sequence for the battery reconnection?

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