idle/AF problems. immediate help needed

[B6Lovin]

ok.. so here's what's going on.

for about the last week my car has had an increasingly erratic idle - this has gone from a 75 or less rpm dip to such a large bounce that the car was occasionally stalling out.

this has now progressed so far (without me making any headway on what's going on ) that if i don't give the car gas it stalls... it won't idle at ALL. very very occasionally it'll idle for a couple seconds (bouncing between 400 and 1200 rpm) and then it just dies again before i can get up front and try to listen for anything strange.

also, during this time (and especially yesterday after i think *hope* i got my OBD port working) i noticed that when it would idle out the A/F was TERRIBLY rich (11.5) however during driving the car acts like absolutely NOTHING is wrong. (except the wideband is intermittently reading leaner A/F's than what i've been seeing)

same with the idling problem - it doesn't bounce or hesitate at any other rpm... just while idling.

at first i was thinking that this may be an electrical issue or that maybe one of my injectors had shit the bed.... but if that was true i don't think i'd have the rich idle A/F and i'd think my WOT A/F's would be WAY leaner than 11.9/12.1... which is as lean as it gets.

my question and only guess as to what's wrong is this:
could an exhaust leak before the turbo be enough of a problem as to fool both the primary o2 and my aftermarket wideband into thinking that the engine is running leaner than it really is, and consequently make it dump fuel trying to correct the problem and flood out the motor?

i fixed an exhaust leak (TERRIBLE) after my downpipe and before the rest of the exhaust, and noticed that i have one at my turbo to manifold gasket. i guess i could never hear the other one, or maybe it's just now totally let loose... i dont know. all i know is that in the last couple days this idle problem has just gotten terrible and i'm completely stumped. i'm going to try just tightening up the bolts to see if that helps the problem at all (the gasket will get replaced either way.. i just want to get this figured out first before i go chasing down exhaust leaks.)

FWIW - i've never had an issue with a bouncing idle before, and no lean issues since swapping fuel pumps... im just running out of things to point a finger at which can cause a lean and rich condition, bad idle, and stalling motor.

[downhillracer]

IAC. Idle air control. although i think its just controlled through the drive by wire...so hmmm.. take your throttle body out and clean it. Or check your MAF to see if its dirty. Check spark plugs too!

[B6Lovin]

IAC. Idle air control. although i think its just controlled through the drive by wire...so hmmm.. take your throttle body out and clean it. Or check your MAF to see if its dirty. Check spark plugs too!

i'll double check the TB in the morning - but it's brand new and i don't run meth.

spark plugs are also on the list, but it runs just fine WOT.

i have no MAF

[A4 Moda]

Your MAF might be on its way out.

if you have any access to a vag: If you get the code for multiple misfires in all cylinders, i'm 90%+ sure it's your MAF.

GL

[B6Lovin]

Your MAF might be on its way out.

if you have any access to a vag: If you get the code for multiple misfires in all cylinders, i'm 90%+ sure it's your MAF.

GL

ok maybe i didn't make this clear in my sig, any of my threads since going BT, or my last post...

i have no MAF to go bad. i do not use one, and haven't for quite some time. my file is tuned specifically for this, and it has never been a problem before.


additionally, the car isn't misfiring... it's sputtering out. you start it and the revs jump up like normal (right as it cranks up) and then boom - stall.

[A4natomical]

i have no MAF to go bad.

maybe running no maf is catching up to you and biting you in the butt

[A4 Moda]

Do you hear any whining noises from the rear?

Could be your fuel pump dying on you, and/or fuel filter clogged

GL

ok maybe i didn't make this clear in my sig, any of my threads since going BT, or my last post...

i have no MAF to go bad. i do not use one, and haven't for quite some time. my file is tuned specifically for this, and it has never been a problem before.


additionally, the car isn't misfiring... it's sputtering out. you start it and the revs jump up like normal (right as it cranks up) and then boom - stall.

[dougyfresh]

Your car runs off the MAP sensor if the MAF is gone. That might be the culprit. (Yes, I remembered you have no MAF.)

Did Uni disable your SAI stuff within the ECU? There is a lot more than just setting readiness to 'good' in order to get rid of SAI. That will cause idle problems. You most likely have to change a few other maps and can only set SAI to kick on for a minimum amount of time (1sec).

Also, possible boost/vacuum leak could contribute.


This was just dealt with on my car. Now my idle is perfect.

[B6Lovin]

Do you hear any whining noises from the rear?

Could be your fuel pump dying on you, and/or fuel filter clogged

GL

already put in the 034ms upgraded pump and replaced the filter at the same time.

Your car runs off the MAP sensor if the MAF is gone. That might be the culprit. (Yes, I remembered you have no MAF.)

Did Uni disable your SAI stuff within the ECU? There is a lot more than just setting readiness to 'good' in order to get rid of SAI. That will cause idle problems. You most likely have to change a few other maps and can only set SAI to kick on for a minimum amount of time (1sec).

Also, possible boost/vacuum leak could contribute.


This was just dealt with on my car. Now my idle is perfect.

the MAP crossed my mind too, but if that was bad wouldn't my car not run well at WOT either? that's what's bugging me. it runs just fine all the time except at idle. (aside from the slight lean issue)

SAI is totally disabled, they assured me i can take all of it out and i have the blockoff plate.

and kyle -- sorry, but that makes no sense at all. the car is tuned for no MAF - it's a specific file from unitronic and it wouldn't suddenly change itself to want a MAF reading.

time to start looking for boost leaks again, but the car is reading the right amount of boost and vacuum...

[CO AVANT]

My boost was all messed up when my MAP sensor was not functioning.

[B6Lovin]

My boost was all messed up when my MAP sensor was not functioning.

yeah, that's why im thinking it's not the MAP sensor.... but what could it be? do you think that exhaust leak could have anything to do with it? that's really my only guess right now.

[dougyfresh]

the MAP crossed my mind too, but if that was bad wouldn't my car not run well at WOT either? that's what's bugging me. it runs just fine all the time except at idle. (aside from the slight lean issue)

SAI is totally disabled, they assured me i can take all of it out and i have the blockoff plate.

You sure the internal maps are changed? Like I said you can disable readiness but that doesn't completely disable SAI under start-up. (something I learned this week)

Test the MAP sensor first though...

Where is your exhaust leak?

[jessefrank]

I have had similar issues on other cars..One I accidently unplugged the MAS the other was a bad/misaligned TPS.

I read somewhere awhile back in the B5 forum...of someone having Idle problems and it endued up being a misaligned TB.

[B6Lovin]

Well I hooked up vagcom earlier - AND IT WORKED - thank god.

Pulled an assooad if codes, cleared them and 3 came back right away. They were all open circuit codes for the iat, n249, and a f265 code for a map controlled coolant temp sensor...

They were all plugged in but the n249 - but my n112 isn't plugged in either and no code for that... Right now I'm thinking that means a wiring issue somewhere since all those wires run into the same harness bundle under the intake manifold. What do you guys think?

[dirtybrd]

What were to other codes? Any o2 sensor codes? Check your fuses, pull them out one by one and inspect them. The MAP coolant sensor is on the ther. housing. I got that code when I blew a ECU fuse

[diagnosticator]

Your car runs off the MAP sensor if the MAF is gone. That might be the culprit. (Yes, I remembered you have no MAF.)

Did Uni disable your SAI stuff within the ECU? There is a lot more than just setting readiness to 'good' in order to get rid of SAI. That will cause idle problems. You most likely have to change a few other maps and can only set SAI to kick on for a minimum amount of time (1sec).

Also, possible boost/vacuum leak could contribute.


This was just dealt with on my car. Now my idle is perfect.

How does the ECU use the boost pressure sensor instead of the MAF meter for lambda control? The boost pressure(MAP it's not,)sensor, is before the throttle valve and cannot measure manifold absolute pressure as required for a speed-density type substitute lambda control method. Without any real data on engine load, the only controlling factor is preprogrammed look-up table values. While adequate for running the engine, the mapped default numbers don't relate to actual conditions. This also means one of the key benefits of fuel injection can't by used. A carburetor would do as good a job.

I don't understand why running MAFless, is the preferred setup in BT arrangements, to me, it's like preferring a stone tool even though an alloy steel tool is on hand and available, with the end results being seriously compromised, but apparently thats not important to many here. Accurate dynamic lambda control is crucial to achieve maximum performance, so running MAFless is a contradiction toward that goal, IMO.
Any insights justifying MAF disconnect despite the lost performance and lower fuel efficiency capability is requested.

[diagnosticator]

I suspect a loose harness connecton to the TB someware. Or possibly a loose terminal contact connection in the common +vBatt power supply wiring for the injectors and coilpacks. I have to review to confirm, but the same power supply may also power the TB. No fault codes?

[dirtybrd]

I don't run a MAF and my A/Fs are on spot everywhere including idle.

[diagnosticator]

I don't run a MAF and my A/Fs are on spot everywhere including idle.

OK, but how does the ECU control injector pulse width to maintain the specified A/F ratios, how does the ECU know how much air flow there is at any moment? Any idea on how the A/F ratios you say are spot on, would compare to the lambda if actual air flow was a factor controlling the fuel rate?

[dougyfresh]

I don't understand why running MAFless, is the preferred setup in BT arrangements, to me, it's like preferring a stone tool even though an alloy steel tool is on hand and available, with the end results being seriously compromised, but apparently thats not important to many here. Accurate dynamic lambda control is crucial to achieve maximum performance, so running MAFless is a contradiction toward that goal, IMO.
Any insights justifying MAF disconnect despite the lost performance and lower fuel efficiency capability is requested.

I am running a MAF. I just recall when you disconnect the MAF the MAP sensor helps take over. However, the ECU does go into a pseudo limp mode unless the programming is coded to handle no MAF. I haven't fully figured out how ME7.5 works with the MAF unplugged.

[dirtybrd]

That's correct Doug, but only under boost. Diag is asking how the MAP controls fuel being as it doesn't see vaccum, it only sees boost. I'm guessing that the ECU uses the IAT, CTS and primary o2 for fueling, but mostly the latter. If you unplug any of these sensors when the engine is running the o2 has the largest effect.

[B6Lovin]

john, i don't run a MAF because it just just another restriction - in my opinion simplicity is key. keeping things open, free flowing, short/to the point, and as simple as possible has helped me get where i am.

my car runs just fine without a MAF (with the exception of now, although this isnt MAF related in the lease) and i see no reason to have one if it (normally) idles and tips into the throttle just fine.

back on topic - i pulled out the ECU, pulled apart the fuse box, and examined all the wires relays and hidden fuses back there.... didn't find a damn thing wrong. i checked every single wire of any type of importance concerning the malfunctioning units and didn't see anything visibly wrong or out of place.

didn't have a multimeter tonight but i will tomorrow so i'll pull it back apart and get crackin on testing pins. right now i've narrowed it down to the IAT causing the idle since of the 3 codes it's the only one which would affect it - and there was no change when unplugging it today while the car was on.

whether it's the wiring or the sensor i don't know for sure. I'm going to just pick up a new sensor tomorrow and try that - if it doesn't fix it i'll just return it and move on to the wiring... (im hoping it fixes it.)

n249 code has been cleared and taken care of
that coolant sensor code still boggles me though... ive got no idea why im getting that unless it's gone bad too, but i don't understand why it would have - and im not overheating or having weird fan/gauge issues


any more thoughts?

[dirtybrd]

What other codes were you getting?

[B6Lovin]

What other codes were you getting?

there were a few random ones, i think i had one for the oxygen sensor that said signal implausible, a voltage-related one that came from trying to start the car too soon after it stalled, and a couple others i can't remember.

none of those came back though, only the 3 about the n249, f265, and IAT

[dirtybrd]

Check your engine managemant fuses, there are 3 of them in the fuse box on the dash.

[B6Lovin]

I already did that about a million times. Even pulled the fuse box apart to check the wires and connections on the back.

[dirtybrd]

Then you must have damaged the wiring harness when you did the motor.

[B6Lovin]

Then you must have damaged the wiring harness when you did the motor.

that's the only thing i could think of too - for the record i didn't drop the motor back in myself, or remove it myself. i just bolted on the last few goodies (all the shiny stuff) and the rest of the basic hardware. (coolant/oil lines for the turbo and motor, accessories, etc)

unless those sensors just really are dead and i've had a n249 code all along and just didn't know it because of the dead OBD port... also, if the harness was damaged during the install, why would this have not been a problem from the get-go? that's what im having a hard time wrapping my head around.

im hoping that replacing the sensor will fix it. *crosses fingers*

[B6Lovin]

btw i appreciate all the help chris, i remembered you having almost identical problems so i kept trying all the things you had hahaha - hence i checked all the fuses and such extra-carefully.

[B6Lovin]

oh, for anyone wondering -- this is the piece of shit i pulled out from between my turbo and manifold...



cleaned up the surfaces, felt/looked for any highspots or burrs, gave it a gentle sanding/good cleaning and stuck em back together..

no leaks to speak of
spool is a SHIT ton better, i can actually hear my turbo now (not just exhaust sounds), and my car still idles like ass lol

[dirtybrd]

I wasn't blaming you just saying. I just blew another manifold to turbo gasket too. This is the 3rd or 4th one. I've tried everything, different gasket material like copper, stainless, lock tabs, blah, blah, blah. I'll be running a knife sharping stone over the mating surfaces to make sure they're perfectly flat and not running a gasket this time.

[dougyfresh]

oh, for anyone wondering -- this is the piece of shit i pulled out from between my turbo and manifold...



cleaned up the surfaces, felt/looked for any highspots or burrs, gave it a gentle sanding/good cleaning and stuck em back together..

no leaks to speak of
spool is a SHIT ton better, i can actually hear my turbo now (not just exhaust sounds), and my car still idles like ass lol

Looks very familiar. Did you check your studs? I bet they are loose and backed out. That will cause an exhaust leak (In addition to mis-matched faces of the T3 flange).

I think you and Chris need to step up to 10mm studs or just drill out for a self-locater pin like what the trans uses. This way the weight of the turbo will be on the pins and not the four studs.

I was blowing out 8mm studs and gaskets left and right earlier this year. When I built my motor I went to 10mm studs and have had NO problems since.

[dirtybrd]

I have larger studs already. I'll be fixing it for the last time, I promise.

[B6Lovin]

doug, the pins are a good idea. studs were fine, they don't appear to have backed out at all, the nuts were definitely loose - my friend brought up that same point that maybe the studs backed out and not the nuts so we made sure everything was nice and tight.

next time i have it all off i'll put some marks on the ends so i can tell for sure what's getting loose (if there is a next time.)

[dougyfresh]

If the nuts are loose then the 8mm studs won't work with that set-up. The nuts kept loosening up for me and at times the studs would loosen up too.

Add pins (Greg's idea) or have it machined and tapped for 10mm studs. Problem solved.


Its common with a design whereas the turbo is cantilevered like the manifold Chris & I have and the one you have.

[dirtybrd]

Make sure you're running black oxide or SS grade 8 studs, if not the heat could be letting the stud stretch.

[B6Lovin]

Make sure you're running black oxide or SS grade 8 studs, if not the heat could be letting the stud stretch.

any way to tell outside of replacing them with one of the two so i know for sure?

[downhillracer]

I would try replacing the IAT sensor! That changes the fuel maps, it won't effect WOT because your car runs in open loop at WOT.

[downhillracer]

You can look up the spec and ohm out the sensor to see if it is reading properly.

[dougyfresh]

any way to tell outside of replacing them with one of the two so i know for sure?

For your 8mm studs you want these locking nuts: http://www.034motorsport.com/product...roducts_id=179

If you are not loosening your studs but the nuts are loosening up I would think about this: http://www.034motorsport.com/product...oducts_id=1329
(I have a set I am not using if you want 'em).


This is what I have now: http://www.034motorsport.com/product...roducts_id=146