Weird idle/vaccuum/boost issue

[NastyNogaro]

Well, my car has been running great lately, until the past couple of days. I noticed last night that it was idling a little low on startup, especially after I gave it a little rev, it would drop real low, and slowly climb back up.

Now, today, I was driving back from the gym, hit boost, everything's fine. I come to a stoplight, the car idles so low it almost stalls out. The vaccuum at idle was reading somewhere around -11 or so. It normally sits around -20. Now I tried hitting boost and it's around 6 or 7 psi, so I'm assuming the car is in limp mode because of a boost leak. However, now the idle is fine, I start it up, it idles fine. I wait 5 minutes, start it up again, and it idles like shit again. Vaccuum is back to around -11 to -13. I checked the intercooler pipes, they look OK. I did a visual check of all the boost hoses atop the engine and couldn't find any issues. I checked all the fuses, everything's OK, engine control unit fuse is fine.

I don't have a VAG com so I can't check the codes. Basically I want to know any common spots/hoses to check for now until i can get my hands on an air compressor to do a leak test or a VAG com.

I have a samco TBB, and F-hose, and they are both fine, so they can be ruled out.

Any suggestions?

[Rajan147]

check your lower intercooler hoses, sometimes they work themselves loose, i blew off a hose on the highway and my car was running just fine.

[HotSauce]

Go to Home Depot and build a pressure tester as per AWE's instructions.

You'll think me later.

[NastyNogaro]

Go to Home Depot and build a pressure tester as per AWE's instructions.

You'll think me later.

Did this, pressure tested, couldn't find any leaks, drove the car and it was fine. It still is fine after 2 hours of driving to philly.. boosting properly and all. Still sometimes it will idle low for a few seconds and come back to normal.

Could this be bad spark plugs? It's not misfiring or anything though..

Rajan: I have a FMIC. The pipes are the CX/JHM 1 piece pipes and I couldn't feel any leaks from them even with the little soapy water test.

I guess I'll get new plugs to be on the safe side and hopefully fix the idle issue.

[BITRBO]

^^So how do you know you're not misfiring again?

"...I don't have a VAG com so I can't check the codes..."

The thing I've learned with these cars is that it's all speculation and guessing unless you actually do some logging to see what's really going on... You might very well be misfiring or throwing other soft codes that don't enduce a CEL. By the sounds of your vacuum pressures, something is up with your load at idle.

If I were you, I'd VAG it asap.

[NastyNogaro]

I will definitely VAG it. Last time the car had a cyl 4 misfire, I felt/heard it sputter and it was very noticeable. However, this seems to be a slight variation of the same symptoms because the idle was a little weird when it had the misfire last time.

I guess I need to buy a vag cable unless someone in northern NJ has one?

[JDM EJ1 95]

brake clean for diagnosis..

[highPSI-S4]

If brake cleaner doesn't work what is the next step?

[RedRocketS4]

how's your MAF? have you tried unplugging it when it starts to act up while idling?