Terrible idle until engine is warm. Please help.

[adam355]

98 TSi with B16G and all supporting mods except injectors.

Anyways whenever I start the car the idle fluctuates from like 1500 RPMS to like 300 RPMS until the engine is warm and it kills sometimes when the RPMs drop unless I give it gas. But once the engine is at 100 percent operating tempurature the car idles almost perfect. Does anyone have any idea what I need to replace?

 

[King Salami]

How do your low fuel trims look?
(I'm assuming you've got the fuel trims under control w/ the SAFC.)

My slightly modified 1G does the same thing, but it's because I took the lower honeycomb out of my MAS & my low fuel trim is at 139% (no fuel control). It idles really low until the 02 sensor warms up.

You might also check the ISC motor - it is a suspect when you've got a bouncing idle.

 

[darknessofay]

might want to check your coolent temp. sensor, i had to replace mine becouse it took like 12 times to start the car when it was cold but when it was warm it cranked up like it was new.

 

[adam355]

Im pretty sure all my honeycombs are in. The cold idle has been gradually getting worse. Like it used to just bounce down to like 500 rpms, but now I have to rev it so it doesn't kill it's so bad. I'll check into the coolant sensor. Is there anything else it could be?

 

[dbritt]

could be your idle switch

 

[crankbender]

could be your idle switch

Also it is possible that it is your FIAV...there are so many possibilities.

First leak check the entire system. Then check your temp sensor. Pay attention to your gauges and logger...does it go away when the 02 sensor heats up?

 

[adam355]

Sorry I havent responded, I am computerless right now and I had to wait for my PDA to get refurbished before I could check the logger. Anyways the coolent sensor temp on the PDA seems to be working correctly. The fuel trims are also pretty good. Anyways, how do I tell on the logger when 02 1 is heated up all the way? Thanks

 

[dbritt]

It's when the voltage starts swinging back and forth instead of just creeping slowly.

 

[adam355]

Whats the FIAV?

 

[flinguist]

Whats the FIAV?

Fast Idle Air Valve, it's on the bottom of the throttle body. Here's a post with info. on the FIAV and some other stuff that may help you solve your problem.http://www.dsmtuners.com/forums/showthread.php?t=134581&highlight=fiav

 

[King Salami]

I agree w/ crankbender - the first thing to do is to pressure check your intake system to make sure you don't have a vacuum leak. Is your boost guage showing 17 - 19 in/hg while idling?

 

[Grimis]

I agree w/ crankbender - the first thing to do is to pressure check your intake system to make sure you don't have a vacuum leak. Is your boost guage showing 17 - 19 in/hg while idling?

im having the same problem, well not the same, but my boost gauge is showing 17-19 vac when idling, doest move i think it sits more at 18 then any thing.

and is't it the IAC instead of the ISC?? Haynes calls it the Idle Air Control Motor?

 

[adam355]

I agree w/ crankbender - the first thing to do is to pressure check your intake system to make sure you don't have a vacuum leak. Is your boost guage showing 17 - 19 in/hg while idling?

no 15, i take it i got a leak?

 

[SpeedFreak03]

Maybe a slight leak, its SUPPOSED to be around 17-19 but its ok if it's a little lower. But, since you have idle problems id check that first. If your car runs and idles fine then 15 is alright tho, but I'd say thats the lowest it should be with stock cams. I'd pressure-check the entire system like crankbender and King salami said.

and is't it the IAC instead of the ISC?? Haynes calls it the Idle Air Control Motor?

Yeah Idle Air Controller (IAC) and Idle Speed controller (ISC) are the same part, just two different names.

 

[Grimis]

Yeah Idle Air Controller (IAC) and Idle Speed controller (ISC) are the same part, just two different names.

Thanks, im like WTF, two names, no wounder we bash are heads when we cant find something

 

[adam355]

Maybe a slight leak, its SUPPOSED to be around 17-19 but its ok if it's a little lower. But, since you have idle problems id check that first. If your car runs and idles fine then 15 is alright tho, but I'd say thats the lowest it should be with stock cams. I'd pressure-check the entire system like crankbender and King salami said.


Yeah, 15 is the highest it gets when idling. Its usually 14. I'll get it pressure checked then get back to this thread. Thanks for the help.