[Jakobw5]

Alright so I've been chasing this issue (extremely rough idle only when the SAI system is running) for awhile now and my car finally threw 4 codes during the warm up process. 3 of which were misfires, exactly what im feeling, and the fourth being a po411 (SAI incorrect flow).

My N112 is plugged in and working correctly sending vacuum to my Combi Valve. New vacuum line, no leaks. My SAI pump kicks on and is blowing air to my combi, I know this because I separated the metal tube from the combi valve and air was blowing strong and I can hear the pump running. As soon as everything kicks off, car instantly smooths out and you can hardly notice its even on.

When I purchased the car the previous owner has some of the solenoids mixed up and the combi valve would stay open im guessing all the time he owned it. and the black pipe leading to the combi wasn't event screwed in all the way maybe a 1/8" gap. Could my combi valve be clogged not allowing air to get threw? Any thoughts on the issue would be great!

Car: 2000 Passat Wagon 1.8T

 

[Tomvw]

An SAI leak, faulty SAIP, or leaking Combi valve will not affect performance.
The only thing likely to cause your issue is a leak, in the N112, the Combi diaphragm, or the hose between them.

 

[Jakobw5]

Interesting, yeah the rough idle is only during the SAI start up, it sure does sound like a vacuum issue, cause its sucks and stumbles and makes this choking noise. How would the n112 leak and what about the combi, it's definitely not the hose between the two.

 

[Tomvw]

Apply vac to combi valve and block it, if it doesn't hold vac the diaphragm is leaking.

 

[Jakobw5]

I can get a brand new combi valve for 60 bucks so I think I'm just going to save the time/money in either renting or buying a hand vac pump and just buy it, honestly what else could be causing a rough idle during the SAI warm up. That's the only thing that could be causing that vacuum leak.

If anyone else has any more ideas on what would cause a rough idle ONLY during SAI warm up please chime in, and no it's not leaking injectors, I've had those checked already.

 

[Jakobw5]

update: started the car cold this morning took the vacuum hose off the combi valve and held it with my finger, it didn't idle as rough but still this noise coming from the air box every 5-10 seconds it sounds like chocking any ideas what that noise is

 

[Jakobw5]

Every time it made the chocking coughing noise the engine stumbled, misfires in every cylinder

 

[Jakobw5]

Here is the video of what is happening

 

[2002GLXV6]

Why don't you try removing the SAI relay and then see how the engine preforms on a cold start?

 

[FrescoGreen01.5]

All the SAIP does is add filtered ambient air to your exhaust (via the combi valve). That shouldn't affect performance, but clearly something is.

I can think of two possibilities:
1. As TomVW suggested, a vacuum leak in N112, the hose, or the combi valve, letting extra air in to the intake.
2. The suction side of the SAIP is somehow affecting the air metering, i.e. the MAF.

(1) seems more likely. In fact, a leak in that hose is what prompted me to write the vacuum hose DIY (in the info base). To test, I'd just unplug the electrical connector from N112. You'll get a P0411 and a code for N112 open circuit, but if the engine idles smoothly you've narrowed the problem significantly. (Given that the PO had the valve connectors swapped, I wouldn't count on the vacuum connections to be right, either.)

If the above doesn't smooth the idle, look at the air box for (2). The SAIP should get filtered, but unmetered air. It wouldn't be easy to mess this up, but it seems in the realm of possibility. SAIP air should not pass through the MAF.

 

[Jakobw5]

Why don't you try removing the SAI relay and then see how the engine preforms on a cold start?

Alright so I did exactly as you said and it worked! I removed the relay and unplugged the n112 and this is the video of the startup

Tomorrow morning I will plug back in the n112 and see if I it is a vacuum leak. My question is, could the SAI pump somehow be sucking to much air from the airbox somehow altering how much air is going into the engine while the pump is running? If that's the case I will purchase a small filter for the SAI hose and block the hole in the airbox.

 

[Tomvw]

My question is, could the SAI pump somehow be sucking too much air from the airbox somehow altering how much air is going into the engine while the pump is running?

If that's the case I will purchase a small filter for the SAI hose and block the hole in the airbox.

No! Not unless the filter was very badly blocked, and it isn't that bad.
Don't make modifications while trying to find a fault.

Properly check what has been suggested.

 

[Jakobw5]

No! Not unless the filter was very badly blocked, and it isn't that bad.
Don't make modifications while trying to find a fault.

Properly check what has been suggested.

Sounds good Tom. I'll leave the relay out tomorrow morning and plug in the n112 and see if I have any symptoms and I'll report as soon as I get into the office!

 

[Jakobw5]

Morning Update: Still have the relay pulled for the SAI system, I tried plugging back in the n112 plug this morning without the relay and it didn't seem to work, im assuming the relay also controls the n112 because I unplugged the vacuum line into the combi valve and there was no vacuum during the warmup process. Tomorrow I plan to put the relay back in then unplug the pump. I want to see if the combi valve/n112 is the culprit causing the misfires. Please feel free to chime in if anything I just said isn't correct!

Thanks again guys,
Jakob

 

[Tomvw]

The SAI relay does not control the N112.

Properly check what has been suggested.

 

[Jakobw5]

Well new update, today I decided to clean my intire intake system/hoses/intercooler get all the oily residue out. And guess what I found. I MASSIVE tear about 3 inches long in my Induction hose right before my turbo. It also looked like the previous owner tried to use electrical tape to cover up the tear and the tape had completely failed! COULD THIS BE MY ISSUE WITH MY WARM UP ROUGH IDLE?????

 

[Jakobw5]

Update: Taped up the induction hose temporarily (until my new induction hose arrives) every single issue I've had has been fixed

1. Rough idle during warm up
2. Pressing the clutch in at high RPMs and the car dies

 

[Steve in Chicago]

Looks like you found the problem. Let us know how it responds when you get that new hose installed.

 

[Jakobw5]

Update as requested: new red silcone induction hose installed, decided to get rid of the air box and put a cone filter on with a custom built aluminum heat shield. No issues for over a week now, fires up every time idles great, I can push the clutch in at any RPM and it WILL NOT stall!

 

[scotts13]

I wouldn't have done the cone filter if I were you, heat shield or not - it's still probably drawing hot air from under the hood. But hey, it's running better than it did, despite that...