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View Full Version : Rough idle, Stalling, No clue, pulling hair out



RastAudiA4
01-28-2015, 11:55 AM
So interesting thing here that's been making me want to bang my head against a wall. Main issue is that my idle is rough bouncing between 900 and 600, sounds like a misfire at idle but no misfire codes,
To explain this to my best ability, the car wants to stall out coming to a complete stop while still on the brakes, just about right before the momentum change when stopping completely, and drops real low but fights to stay alive, and it does sometimes and other times it will stall. As well as when i press the clutch it does the same thing whether i am on the brakes or not but only in low rpms, still rolling to a stop, 1st to neutral or neutral to 1st...w.e, i can repeatedly press the clutch in while rolling and it will repeatedly drop in rpms almost stalling. If im sitting still i can pump the brakes continuously and then hear the idle return to normal but drop again soon as i stop pumping the brakes.

I thought it could be the brake booster vacuum lines because it only happens when i brake/clutch in at low rps around 1000 and below. So i did the SJP simplify just like walkytalky's guide as well as everything else to delete/simplify but the breather system hoses....which i inspected and seem fine. This made it better and stall a lot less, BUT it is still happening. i then checked the hose going to the brake booster itself and it checked out fine no leaks......

So i have done the n249 bypass, and one day i accidentally pulled the line going from my forge spltr top nipple to the intake and the car idle perfectly...I then plugged the line with my finger still connected to the intake and it went back to running rough....ok, now obviously that line can't be and left off because its directly off the Manifold Nipple, and when its plugged/ installed on the forge split r's nipple it runs rough...when its off im not boosting fully, and the spltr flutters as if its too tight, no matter the clicks. Thing is, when braking the idle still drops, just so lightly, but never stalls nor fights....

any ideas? this is the best i can explain this....
car is a atw quattro
what i've done:
boost leak test
evap delete
sjp delete
n249 bypass
sai delete with block off and vac line rerouted
forge spltr
k04@15lbs
mbc
3" test pipe
fmic
samco tip checked for leaks

ray4624
01-28-2015, 02:26 PM
try it with the stock DV and see if it changes.
Maybe your splitter needs to be lubed or it is sticking open.

RastAudiA4
01-28-2015, 04:34 PM
try it with the stock DV and see if it changes.
Maybe your splitter needs to be lubed or it is sticking open.

I already got a rebuild kit for the splitr valve from forge, and they say not to lube the valve, it is supposed to operate dry, i know for a fact that the splitr stays open at idle until throttle response, don't have a stock dv, car came with the forge splitr, i have it running 50/50

ray4624
01-28-2015, 04:46 PM
the splitter does not stay open at idle. I had one...it was closed.
Your splitter is not working correctly.
If it is open at idle then it is creating a huge leak of unmetered air which seems to cause all your problems.
Make sure it is installed correctly. The splitter gets installed in the reverse orientation as the stock valve. The PO may have screwed that up.
either way, it needs to be closed at idle.

RastAudiA4
01-28-2015, 05:17 PM
its installed correctly, charge pipe at the bottom, tip on the side, according to multiple forge employees, and a 10 min wait on the phone to contact more forge employees, the splitr is supposed to be open at idle 0_o,
there is not much to the splitter valve, just a piston and a spring, i don't see how it could not work with a new piston and spring, the vacuum line to the Intake is what's supposed to keep it open. And even with that, the car acts the same as me plugging that vac line with my finger as well as installing it to the forge valve nipple

Seerlah
01-28-2015, 05:33 PM
Unplug your MAF and see if it idles correctly.

RastAudiA4
01-28-2015, 06:00 PM
Unplug your MAF and see if it idles correctly.

i've done that :( nothing changes, could the map sensor cause that? The PO half assed it with jb weld

ray4624
01-28-2015, 06:03 PM
its installed correctly, charge pipe at the bottom, tip on the side, according to multiple forge employees, and a 10 min wait on the phone to contact more forge employees, the splitr is supposed to be open at idle 0_o,
there is not much to the splitter valve, just a piston and a spring, i don't see how it could not work with a new piston and spring, the vacuum line to the Intake is what's supposed to keep it open. And even with that, the car acts the same as me plugging that vac line with my finger as well as installing it to the forge valve nipple

interesting. The whole point of putting it on a car with a maf is that it is closed at idle. Same way my forge 004 is closed at idle
Do you have the cap to put it into re-circulation mode?

RastAudiA4
01-28-2015, 06:07 PM
interesting. The whole point of putting it on a car with a maf is that it is closed at idle. Same way my forge 004 is closed at idle
Do you have the cap to put it into re-circulation mode?

sadly no, i've been trying to come up with something to block it, and test, you think just taking off the horn and placing my hand over it at idle is enough to simulate the recirculating event? or does it need load applied?

ray4624
01-28-2015, 06:08 PM
maybe. if the rough idle goes away then you have found your problem.

RastAudiA4
01-28-2015, 06:25 PM
ok will deff try that in the AM and update, how can i tell if my MAP sensor is working?

ray4624
01-28-2015, 06:31 PM
that i do not know. my car has no map or n249

RastAudiA4
01-29-2015, 01:34 PM
So i tried blocking the horn side and just running it recirc, doesn't change a thing. plugged out map sensor, nothing changes, double checked all the IM hoses for leaks just by feeling around, nothing. i contacted forge again they agreed to replacing the valve just to be 100% and cross it off the list.

So i know they're are different scenarios of idle, High idle, Low idle, and Bouncing/rough idle, i fit into the low/bouncing idle category, does that say anything?

Can you guys understand whats going on clearly from the posting or will a video better explain? the video pretty much portrays exactly as i wrote

RastAudiA4
01-31-2015, 10:11 AM
anyone? anything to check? gotten worse to the point where i can't run the car without having that line from the intake mani going to the splitter valve disconnected