Starting Idle RPM?

[Runnin'OnEmpty]

My X's idle runs up to about 1800 rpm immediately when it starts, and then drops down to normal, about 650-700 rpm. It has done this since I bought it (3 months ago), and it runs perfect.

Is this normal, or a sign of an intake manifold leak?
Thanks.

 

[Alec]

How long does it take it to drop down to normal?

If it drops down in a reasonable amount of time and otherwise idles and runs well then I'd say it's normal. 1800 is a bit high, but many Explorers have a high initial idle then drop back down.

 

[Runnin'OnEmpty]

Thanks for the reply, Alec. It drops back down within 4-6 seconds. I didn't think anything about it until I started reading all these threads about the intake O-rings leaking.....

It also has a slight "whoosh" noise when going uphill at low speed and low rpm. This also made me think of the O-rings. There's no MIL though, and the truck runs fine.

 

[MontanaGT]

Don't cars have automatic chokes? I thought that they did because all of my cars have done the same thing. My Ex revs high at start-up (about 1500 RPM) but only takes 5-8 seconds to drop to 700 RPM. This time is longer in the winter, up to 30 seconds. I don't know about the "whoosh" going up hill.

 

[Opera House]

Automatic choke

Is now a function of the fuel injector. The computer senses the air intake and the engine temperature and turns the fuel injector on for a longer time to make the fuel to air ratio "richer" when cold. The IAC allows the computer to set a reasonable idle for the conditions.

 

[miausa2003]

Up and Down RMP at start-up

I have a 98 XLT, 4x4. I have a SOHC V6. Everytime i start my truck up in the morning it gets the cold syndrome. The engine Revs up high 1500 and then drops to under 500., a few seconds later up to 1500 and then down again. If I let it sit with out accelerating, the engine will eventually turn off because of the low RPM's. Now if I take the car out and drive a few blocks and let the engine heat up, the problem goes away and the engine runs smooth for the remainder of the day. But when i initially start the engine in the morning, I get this problem of the Up and Down RPM's. Anyone have any suggestions?

 

[Majisto]

Re: Up and Down RMP at start-up

Originally posted by miausa2003
I have a 98 XLT, 4x4. I have a SOHC V6. Everytime i start my truck up in the morning it gets the cold syndrome. The engine Revs up high 1500 and then drops to under 500., a few seconds later up to 1500 and then down again. If I let it sit with out accelerating, the engine will eventually turn off because of the low RPM's. Now if I take the car out and drive a few blocks and let the engine heat up, the problem goes away and the engine runs smooth for the remainder of the day. But when i initially start the engine in the morning, I get this problem of the Up and Down RPM's. Anyone have any suggestions?

Oh gosh, not again.. It's the idle air control valve that is doing this most likely. Have it cleaned out, and it should fix this very, very common problem on Fords.

As for the engine idling high, this is perfectly normal. It is a feature built into cars with catalytic converters to warm the cats up faster for emissions purposes. A cat doesn't function well when it's cold.

 

['96explorereddiebauer]

Yeah...sounds like the IAC to me.

On mine, it revs to about 1500rpm at cold start and then drops to about 800rpm when it is warm enough.

 

[TPLYNCH]

Re: Up and Down RMP at start-up

Originally posted by miausa2003
I have a 98 XLT, 4x4. I have a SOHC V6. Everytime i start my truck up in the morning it gets the cold syndrome. The engine Revs up high 1500 and then drops to under 500., a few seconds later up to 1500 and then down again. If I let it sit with out accelerating, the engine will eventually turn off because of the low RPM's. Now if I take the car out and drive a few blocks and let the engine heat up, the problem goes away and the engine runs smooth for the remainder of the day. But when i initially start the engine in the morning, I get this problem of the Up and Down RPM's. Anyone have any suggestions?

Before jumping to the IAC, first question to ask you is..

Have you had the 00M12 and 01M01 owner notification program work done? These cover the manifold O-rings and the cam chain tensioners.

If the IAC was bad, it would be rough all the time. Rough idle/stall on startup until the engine is warm is the classic symptom of the O-rings being bad. Ford will replace up to 72K miles. Search for 00M12 and you'll find out alot more about the problem.

 

[natedogco2007]

i know that this sounds kinda wierd but this link seems to be active. i have an idle problem. when i crank up the ex it revs high ( 1500 ) then calms down to about 600 revs, but when i drive it and stop and put in park the car idles back up to 1500 revs. this happened one other time and the temp sensor was bad but it was only about 700 miles ago that i had it changed. i don't think that it would be bad that fast. any suggestions to what it might be?

 

[Majisto]

Originally posted by natedogco2007
i know that this sounds kinda wierd but this link seems to be active. i have an idle problem. when i crank up the ex it revs high ( 1500 ) then calms down to about 600 revs, but when i drive it and stop and put in park the car idles back up to 1500 revs. this happened one other time and the temp sensor was bad but it was only about 700 miles ago that i had it changed. i don't think that it would be bad that fast. any suggestions to what it might be?

How is the thermostat looking?

 

[rkj082000]

I second the o-rings and the cam tensioner, I had the exact same problem, and this ended up fixing it. Dealer did not charge me for the work.