Bad FIAV. What do I do?

[avaholic]

Hey all, my 93 TSI AWD has a pretty bad idle surge, and have narrowed it down to a bad FIAV. I've been reading up on this a ton but I can't post in any of those forums since I'm a new member . I've decided to block off the FIAV but don't know whether to block it off completely with a block-off plate, or to retain the ISC with a bypass plate. The ISC is new and I live in Colorado and know that cold start ups can be difficult with a complete block off. I just don't know if a bypass plate would do the job or not since the only reason I'm blocking off the FIAV is to fix my idle problem. Any suggestions?

 

[Avionixx]

I too had an idle surge issue and I retained my ISC with a bypass plate. The idle surge was fixed and have no issues with cold starts (though it doesn't get THAT cold here in Cali), but I did notice stalling and severe RPM dip when the clutch is depressed at too high a RPM. I say go for it.

 

[9!'clipseDOHC]

The FIAV only raises the idle while the engine is cold. Is your erratic idle only when the engine is cold or even after it warms up to normal operating temps?

 

[BlackMount]

The FIAV only raises the idle while the engine is cold. Is your erratic idle only when the engine is cold or even after it warms up to normal operating temps?

something often overlooked is the idle being turned up to high some how on the car, and so it will raise up in idle, then the ECU will go wtf and cut it so it drops, then as soon as it gives it fuel or w.e it cut back, it raises again. resulting in the idle going up and down in a steady pattern.

try turning your idle down. I had similar problem on my first DSM, and turned out it was just my idle being way too high.

 

[avaholic]

It idles high right when I start it and then even higher (around 2000 rpms) as it warms up. The idles switch is unhooked right now because when I do hook it up it starts going up and down between 1300 and 1500 rpms every second or so which is consistent with what I found on idle surge here Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)
The question I was asking is whether I should use a block-off plate or a bypass plate to retain the ISC?

 

[BlackMount]

It idles high right when I start it and then even higher (around 2000 rpms) as it warms up. The idles switch is unhooked right now because when I do hook it up it starts going up and down between 1300 and 1500 rpms every second or so which is consistent with what I found on idle surge here Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)
The question I was asking is whether I should use a block-off plate or a bypass plate to retain the ISC?

ohh my bad, I miss understood what you were asking help on.

 

[avaholic]

And Blackmount, I have messed with the BISS already. When I bought the car the BISS was missing completely and when I installed a new one it didn't do much with the idle. It's now currently screwed in all the way and still having the same idle issues.

 

[Calan]

And Blackmount, I have messed with the BISS already.

That's most likely a lot of your problem. You don't "mess" with the BISS; you adjust it correctly using a certain procedure so that the ISC is in the middle of it's range and the ECU can maintain the correct idle.

...I installed a new one it didn't do much with the idle.

Which is perfectly normal if the diagnostic plug isn't grounded. As you turn the BISS, the ECU compensates by adjusting the ISC...until it runs out of adjustment range.

It's now currently screwed in all the way and still having the same idle issues.

As I would expect.

*****

Not to sound like an a$$, but I think you need to do some more reading on how the ECU controls the idle before just yanking components and hoping that it goes away. And you need to check your base timing. The ECU uses a combination of timing and ISC adjustments to maintain the idle as the engine sees different loads.

 

[avaholic]

Haha no worries. I'm completely new to the dsm scene and am still learning so I'll take all the advice I can get! So what exactly are you saying I should try? Checking the timing to see if it's correct? Also, where exactly is the diagnostic plug?

 

[Calan]

There are many threads that cover all of this, but here are a couple links to get you started:

1G BISS Adjustment
Engine Timing
http://www.dsm.org/how-tos/tttt/tttt3.html

 

[avaholic]

I actually used that exact same site to set the BISS, so when I said I "messed with the BISS" I meant I used that site and set it properly . I should probably be a little more specific in the future. I also went to that third site yesterday and that's where I narrowed down to the FIAV and decided that I either needed to block it off, or use a bypass plate and retain the ISC. Is this something you would suggest I do? If so, should I use a block-off plate, or a bypass plate to retain the ISC?

 

[Calan]

Unless you are using some sort of stand alone tuning system (and have a lot of patience), you don't want to bypass the ICS. It is what the ECU uses to modulate the airflow through the TB to maintain the idle.

 

[avaholic]

I'll order the bypass plate then. Thanks a ton for all the help!

 

[9!'clipseDOHC]

Level Zero Motorsports sell the bypass plates for $10.00 shipped. Best deal I've seen. This is where I got mine.

 

[avaholic]

Yeah, I just ordered it off of their ebay store! Thanks again for all the help, and I'll elt you know if the bypass plate does the job!

 

[DSMopar]

Waste of cash dude, wish I had seen this thread earlier. Just pick your favorite tube of RTV and plug the FIAV holes (leave ISC open)... problem solved no stupid bypass plates to dick with or cause leaks...

 

[DsM KiD4]

Waste of cash dude, wish I had seen this thread earlier. Just pick your favorite tube of RTV and plug the FIAV holes (leave ISC open)... problem solved no stupid bypass plates to dick with or cause leaks...

I wouldn't use rtv to fill the fiav ports in the throttle body or to block anything for that matter. RTV is typically used to create a gasket or help seal gaskets. If you use rtv for this , at least use the black one. If you want to fill the fiav holes in TB I would suggest JB weld to assist the blockoff plate from leaking boost. I also used JB weld on the water line to block off the coolant going to, and from the throttle body. Also to the 91+ oil filter housing now that i run a 1990 setup.

 

[avaholic]

Good to know, thanks!

 

[DSMopar]

Pff, you'd be amazed at what the right RTV will seal, problem is no one recognizes how critical cleanliness is. Everyone does this with FIAVs, easy fast and cheap. Mine's been like this for 2 years, dead steady idle.

 

[tunethis]

I used quiksteel putty on one FIAV I blocked and I blocked off another FIAV by screwing the spring in all the way. My idle held perfect using both methods. No plate needed.

 

[Hesh724]

I had done the entire check list of idle issue remedies plus lots of other stuff! heck i got a valve job cause of it and it all ended up being my FIAV. i just took my T/B off split it knocked out the freez plug. turned that valve all the way in with some needle nose pliers reinserted freeze plug. then i made a fiber BYPASS gasket i left the isc oprable. and blocked off the coolant nipples. it fixed my idle surge. only now my engine acts like it has a choke till it warms. my foot being the choke adjustment . but works great just hold the gas pedal a hair when you first start it and hold it till it warms a hair. youl be fine! or try to readjust that valve that i said turn all the way in but have fun finding the right spot now that spring has worn soft.

 

[avaholic]

Glad to hear it can be a fairly easy job! Do you happen to have any pics of the TB when it's split revealing the freeze plug and valve that you need to turn in?

 

[avaholic]

So the bypass plate came in the other day and I just installed it today (along with a good thorough cleaning of the TB) and it worked like a charm! Car is idling smooth and steady! I have already noticed a little bit of issues with a cold start, but with a little bit of gas it starts just fine.

My car did however, start heating up a lot faster and my car already had some overheating issues before. Is this something to be concerned with?

 

[9!'clipseDOHC]

So the bypass plate came in the other day and I just installed it today (along with a good thorough cleaning of the TB) and it worked like a charm! Car is idling smooth and steady! I have already noticed a little bit of issues with a cold start, but with a little bit of gas it starts just fine.

My car did however, start heating up a lot faster and my car already had some overheating issues before. Is this something to be concerned with?

Overheating is something to be concerned with, but the FIAV bypass has nothing to do with it. It will run like its at normal operating temps from the get go, but it won't make it run any hotter.