Why is my IDLE so HIGH at startup? [Archive] - DSM Forums: Mitsubishi Eclipse, Plymouth Laser, and Eagle Talon Forum: DSMtalk.com

: Why is my IDLE so HIGH at startup?


GSX6bolt
12-10-2006, 10:05 PM
At startup whether its hot, or cold out, my cars idle will start out around 1500, and then climb to nearly 3k rpm....After about 10 mins of warming up, the idle jumps down to around 850.

It hasnt been tuned in awhile, but other than that, I got no clue as to whats going on. Any help would be greatly appreciated.

faithless
12-10-2006, 10:27 PM
ECU dumps fuel with cold starting temp to warm up car faster. It is normal.

Boost_Addict
12-11-2006, 12:22 AM
Start it, let it run for a few seconds, and rev it up a bit(just once), that might help drop it down.

jreese86
12-11-2006, 07:13 AM
My car does the ame thing, only instead of going to 3k it's capped at like 2300, so it revs up, hits 2300 and drops down to 1500, then revs back up again until it has time to warm up and drop back down to ~800. Quite annoying, especially in the morning.

greenstreak
12-11-2006, 07:44 AM
It is normal to have a high idle when cold. The FIAV (fast idle air valve) is doing it's job.

spoulson
12-12-2006, 09:02 AM
What is the usual high idle revs on cold startup for others here? 3k is pretty high.

94_Talon_ES
12-12-2006, 10:20 AM
The highest mine ever goes on a cold start is 2000.

bdubbs
12-12-2006, 11:26 AM
mine goes up to 1500 thats about it.

Eric_7810
12-13-2006, 12:39 PM
This fast idle valve in the TB is something that I think was only on the 1g's, cuz on my 97 it idled calmly, but when I let my 91 warm up it screams, this HAS to be pissing my neighbors off at 6am.

91Bluebird
12-16-2006, 11:46 AM
3000 rpm sounds way too high to me. My TSI and GS idles at 1500 rpms on cold start-ups. Personally I wouldn't want my engine anywhere near 3000 rpm when starting it.

0lmytsi
12-16-2006, 12:11 PM
3k is DEFINITELY not normal. ~1500 is about where it should idle at cold startup.

To the guy having idle surge when the car is cold, it's probably a bad fiav.

empty01
12-16-2006, 05:02 PM
It sounds like something in the TB, maybe FIAV or ISC. My idle was only like that from a cold start before I traded out my bad ISC motor. Now it wont hit past 1850 and even then it lasts for about 5 seconds at most (that includes drop time) before it hits 1250 and then waits to warm up. Not sure about my TPS and FIAV but that ISC is in perfect working order so it leads me to believe taht's around where a stock car should be unless one of the three complex doo-hickeys on the throttle body is going.

GSTQUICK
12-16-2006, 05:05 PM
LOL, 2300-3000! Damn thats high. Mine never see's above 1500rpms when its cold at startup.

greenstreak
12-17-2006, 12:43 PM
Been a long time since I had a FIAV but I believe mine would idle at about 2300 rpm when cold.

apex
12-17-2006, 07:53 PM
1.5k rpms on a cold engine, 1.1k with block heater, and 1.8k on extreamly cold days.

the heis
01-13-2007, 10:54 AM
I realize this is a dead thread, but I have a problem related to it and didn't want to start a new one. My idle is high at startup but ONLY after the engine has been warmed up. For example, if I drive around town and stop to go in a store. When I come out and start my car it idles high at about 2200, but then goes down over time. I'm thinking this has to do with the FIAV as well, any ideas?

0lmytsi
01-14-2007, 10:31 AM
It's the ISC. FIAV controls idle on cold startup and the ISC takes over once its up to temp.

91slowgst
01-18-2007, 02:35 AM
It's the ISC. FIAV controls idle on cold startup and the ISC takes over once its up to temp.


I think both of mine are bad...

Cold starting my car goes up to 3500 stays for a couple secs then drops to 2500 and stays there. Once warmed up it bounces around from 200 to 3500 if let idle for more than 45 secs it will bring itself to 400-500rpms. I am looking at all the hoses to check for leaks and will performing a boost leak test. Cel came on then went off (I purchased a datalogger and waiting for it to get here).

0lmytsi
01-18-2007, 06:15 AM
Both are probably bad then. Just hit up a junkyard and get a new throttle body.

el brujo
11-12-2007, 02:31 AM
My 1g starts fine a little high on the idle in the morning but then when it gets warm it will rev up and down like crazy. Also, since it's an A/T, shift changes are really rough. Can 'yall' help me with this problem. I just changed the whole water pump deal with timing belt, changed the wires, spark plugs have about 10k. Thanks guys

faithless
11-12-2007, 07:54 AM
It revs up and down because you idle is set too high. When the ECU sees that your RPM go over 1,500 and your throttle is not pressed and that the car is fully warmed up it cuts the fuel making your rpm drop and go back up. Not sure if it's RPM or Hz dependent. Try setting your idle speed screw. Screw it in half a turn at a time.

0lmytsi
11-12-2007, 02:14 PM
Idle surge is caused by a bad ISC or a vacuum leak among other things but those are the 2 main things. I bet your ISC is bad. Search for IDLE SURGE and read up.

el brujo
11-22-2007, 04:51 PM
It revs up and down because you idle is set too high. When the ECU sees that your RPM go over 1,500 and your throttle is not pressed and that the car is fully warmed up it cuts the fuel making your rpm drop and go back up. Not sure if it's RPM or Hz dependent. Try setting your idle speed screw. Screw it in half a turn at a time.

Ok I turned the idle speed screw as far down as it will go and it still revs up and down like crazy still. I'm thinking it's the timing cause the mechanic installed the timing belt when he did the water pump job. I don't know though :wall:. I did a boost leak test this morning, no leaks. What else could be the problem other than the ISC? Thanks fellas and Happy Turkey Day:).

TravisB
11-22-2007, 05:18 PM
Ok I turned the idle speed screw as far down as it will go and it still revs up and down like crazy still. I'm thinking it's the timing cause the mechanic installed the timing belt when he did the water pump job. I don't know though :wall:. I did a boost leak test this morning, no leaks. What else could be the problem other than the ISC? Thanks fellas and Happy Turkey Day:).
is this before or after the engine is at full operating temp?

when i start mine it idle surges from 1000-1800/2000 then as it gets warmer it will slowly fade away. At full operating temp it will idle around 950

el brujo
11-22-2007, 06:17 PM
It's after it get warmed up. I found the following site:
http://www.dsmtalk.com/forums/showthread.php?t=61643&highlight=idle+surge I'm gonna look there see what I can find. Thanks