Idle Reving 1500-2000rpm

[Dave_Hash]

Went for a drive last night and after about 20mins just driving around I pull up to a stop sign and instead of idling, the car revs back and forth between 1500 and 2000 rpm.

I have checked the ISC and it is fine. I have also reset the ECU three times, waiting over an hour before reconnecting the battery. Checked the BISSS screw and seems fine.

Also when the car starts it sits at 2000 rpm (what it has since I put the 1g throttle body in six months ago) and once it is warm it starts to do the reving between 1500 and 2000 rpm. Before last night it would go down to 750 rpm.

 

[Avionixx]

Are the FIAV lines (the two coolant lines) hooked up to that TB?

 

[Dave_Hash]

Yes they are hooked up. Also last night about 5mins after it started it did throw the CEL P0505.

 

[Avionixx]

I'm inclined to blame the FIAV, but if you're getting an ISC code then maybe you should have another look at it. Or clear the code and see if it comes back.

 

[phillabaum03]

vacuum leaks? IAC? headgasket? idk what else

 

[Dave_Hash]

I'm inclined to blame the FIAV, but if you're getting an ISC code then maybe you should have another look at it. Or clear the code and see if it comes back.

I was thinking the FIAV, but what is it that does go bad in it? I was thinking of getting a block off plate for it.

I did clear it and it has not came back yet but the idle problem is still there.

 

[Dave_Hash]

vacuum leaks? IAC? headgasket? idk what else

Trying to check for vacum leaks, have not found any yet. What is the best way to check?

IAC is the same as the ISC and I have checked it.

As for the headgasket, I am not seeing any other problems that I would expect if there was a problem with a head gasket going.

 

[meliketoball]

Check your throttle cable and TPS.

 

[dsm03]

x2 check the tps..

 

[Boosted_out]

My car was having this same issue. My battery light kept coming on and it finally went on me. I changed the battery and terminals and it hasnt done that since. I still dont understand how the battery effected that either.
I keep waiting for it to come back. I guess I will see

 

[Avionixx]

I was thinking the FIAV, but what is it that does go bad in it? I was thinking of getting a block off plate for it.

I did clear it and it has not came back yet but the idle problem is still there.

Little wax pellet that seals the extra air passage (which allows for higher idle) after the car has warmed up. Obviously if the wax pellet is no longer working as intended, your car will never get out of fast idle. Works a lot like your coolant thermostat, but isn't replaceable or serviceable.

A blockoff plate is one way to fix it and that's what I've done with mine. You might have to hold your throttle open while the car warms up if it gets real cold in your area, but I've never had to do that here with California weather.

 

[itbeatown]

I am running into the same issue. Anytime the car is idling or even has the clutch engaged. It will rev back and forth between 1000 and 2000. But cant find a single issue with it.

 

[mikgsxx]

x3 mine was doing the same thing, ended up the tps sensor was going out.

 

[surfside]

I had the exact issue. It's your fiav for sure. I bought a new ics thinking that it was the problem, it wasn't. I just blocked the fiav and presto perfect idle. enjoy.

 

[Lou98GSX]

check tps for correct voltage at idle should be .063 v . then the other problem could be the the by pass in the throttle body . i have a 1g throttle body on my car and one time it started this idle surge but once it was warm it was fine . what i did to correct this was to follow the road race engineering fix . had to remove my throttle body and there is a freeze out plug you remove then you turn a valve inside the throttle body clockwise . i think i went 1/2 a turn and that brought my fast idle to 1200 rpms . it worked great no more idle surge when cold .

 

[T is for TURBO]

Little wax pellet that seals the extra air passage (which allows for higher idle) after the car has warmed up. Obviously if the wax pellet is no longer working as intended,

There is no wax pellet in the FIAV

OP- my car did this a few days ago. I was driving around doing some 3rd gear pulls here and there. Pulled up to a stop sign and my car would drop to my set 1k idle then slowly make it's way up to 1.5k. Shortly after I noticed my turbo was surging when letting off the throttle. I got home, popped the hood and my vacuum source for my BOV popped off. It made for a big vacuum leak.

Best way to look for a vacuum leak is to simply do a boost leak test.

 

[luv2rallye]

I am running into the same issue. Anytime the car is idling or even has the clutch engaged. It will rev back and forth between 1000 and 2000. But cant find a single issue with it.

Check if the IPS (idle position switch) part of the TPS is adjusted properly. Read post 14 here first for explanation, then post 13: http://www.dsmtuners.com/forums/newbie-forum/255885-bad-tps-again.html#post151940336.

 

[DSM1G90]

Excellent thread on the TPS testing above. Some cars you have to do the voltage testing ... with my little trick was to use straight pins jammed in the back of the plug so they made contact with the inner connectors so I would have test points for my VOM while being connected to the TPS and do the voltage testing.

Seems that most TPS units needs that .5vdc as the magic number for center.