# Let's Play the "Diagnose That Bunny" Game!



## LampyB (Apr 2, 2007)

08 Rabbit - 93 Oct. Tune - CAI - 66K Miles

Alright, I'm at a loss as to what's causing my problem. Experiencing the following symptoms:

-Rough Startup. Either dies out after sputtering for a few seconds, or the rpm's settle and the car has a pretty rough idle. When it sputters the dash lights and digital display will sometimes dim and brighten as the car tries to stay running.

-Prior to the startup issues, the car just had a rough idle and when i held the gas pedal down very lightly with consistent pressure just to hold a speed of say 10mph it would jerk a bit. 

-Last night i was driving home, and the idle became sort of violent, almost dying out and then coming back alive. I don't really know what 'knocking' sounds like per se, but it was almost like it was popping as it tried to remain running.

-I have a CEL, running lean. Generic autozone code that may be due to my CAI (without the maf sleeve), but i'm not 100% on this. 


I have unplugged the MAF and it doesn't change anything, so I don't think this is the problem. I've heard a bad Coolant Temp. Sensor can cause a really rough idle, as well as the possibility of a bad 02 sensor, or bad Catalytic Converter. What about something as simple as a bad battery? I do have 66K miles on the car...

HELP!!! :beer:


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## thygreyt (Jun 7, 2009)

first thing i'd do is check for vacuum leaks...

but then i'd check with my tunner for the code, and the whole issue... cause well.. maybe he knows more (he should.)


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## tay272 (Aug 22, 2007)

That deffinately sounds like an MAF problem to me although it could also be a vacuum line. If you unplugged it and nothing changed then thats most likely your problem. Unplugging that sensor normaly would just make the car shutoff immediately.


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## LampyB (Apr 2, 2007)

so when i unplug the MAF and symptoms don't change it points toward this being my problem? my last 5 cars have all been VW/Audi turbo's, so this is new to me. in my 2.0T GLI and my old 1.8T's if you unplugged the MAF and the car responded positively then you had a bad MAF sensor. our cars don't have a MAP sensor that takes over for the MAF?? sorry for the noob questions here, i'm accustomed to resolving turbo issues...


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## nothing-leaves-stock (Mar 1, 2005)

tay272 said:


> If Unplugging that sensor normaly would just make the car shutoff immediately.


sorry, thats incorrect.
unplugging the maf throws it into a "safe mode" type thing. so if you have a bad maf and you unplug it and it runs better or OK...the maf is normally bad. if it doesn't change...9-10 its not bad. thats not ALWAYS the facts tho, but most of the time.

up stream 02, maf or coolant temp sensor could cause issues like that. also look for vac leaks but thats not as common on the 2.5L
my 07 had an issue with the throttle body but that was cutting in and out


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## LampyB (Apr 2, 2007)

what did you do to resolve the throttle body issue? cutting in and out is a small symptom that i'm experiencing, like i said above when holding down the gas pedal consistently to hold a low speed of say 10mph. the car stutters when i do this, like the throttle is going in and out. when i press down normally with adequate pressure during acceleration everything's fine though. 

i'm going to open up my TB to see if it needs a cleaning, but i don't have a garage and it was raining buckets yesterday. what could cause the TB to actually go bad?


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## nothing-leaves-stock (Mar 1, 2005)

yes 07-08 had TB issues. cleaning does not work. you must replace IF thats the issue


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## LampyB (Apr 2, 2007)

i'm going to pick up a coolant temp. sensor today from VW, its worth a shot for under $20. wouldn't a bad oxygen sensor throw a code?

EDIT: when replacing the coolant sensor (the one up top above the trans), i've done this before on an Audi and coolant shot out everywhere. will unscrewing the reservoir cap relieve all pressure so it doesn't explode when i remove the sensor? what's the best way to do this...?


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## thygreyt (Jun 7, 2009)

the sensor is on the outside...

dont even have to open the bottle.


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## nothing-leaves-stock (Mar 1, 2005)

Not true.

The sensor is in a plastic housing held in with a clip. If you pop it out under pressure, coolant will spray out. Just release the pressure by unscrewing the cap. Then you can pop the sensor out quick with very little coolant loose or mess


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## LampyB (Apr 2, 2007)

Yep, thats what i thought. Thx guys. Btw stealer charged me $30 for the sensor...robbery! Oh well, dont have time to wait for it to be shipped online.


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## thygreyt (Jun 7, 2009)

nothing-leaves-stock said:


> Not true.
> 
> The sensor is in a plastic housing held in with a clip. If you pop it out under pressure, coolant will spray out. Just release the pressure by unscrewing the cap. Then you can pop the sensor out quick with very little coolant loose or mess


just to confirm, isnt the sensor, the thing thats plugged on the bottle on the outside??


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## nothing-leaves-stock (Mar 1, 2005)

thats the low level sensor.


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## thygreyt (Jun 7, 2009)

oh.. thats the one i was talking about.


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## LampyB (Apr 2, 2007)

the one i've been referring to is below....


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## tay272 (Aug 22, 2007)

nothing-leaves-stock said:


> sorry, thats incorrect.
> unplugging the maf throws it into a "safe mode" type thing. so if you have a bad maf and you unplug it and it runs better or OK...the maf is normally bad. if it doesn't change...9-10 its not bad. thats not ALWAYS the facts tho, but most of the time.
> 
> up stream 02, maf or coolant temp sensor could cause issues like that. also look for vac leaks but thats not as common on the 2.5L
> my 07 had an issue with the throttle body but that was cutting in and out


Ha I knew it was one or the other but unfortunately I was wrong. Listen to Josh on this one, he knows better then me. Thought it was the other way around, my bad.


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## itskohler (Jan 7, 2011)

I've had an awkward idle "shudder" for 2 months. When I took it (still under warranty), they thought it was a vacuum leak as well. Low and behold, that wasn't the problem. I honestly think it got WORSE with them tinkering in the engine bay. They then said its the TB and told me that the item wasn't under warranty because I hadn't gone to them for the 40k mile tune up and went to a dealer alternative instead. Who is a certified dealer altertnative from VAG (f-ing crazy right? :screwy I haven't replaced it yet. I'm waiting for some other things for my car to roll in so I know for a fact that the TB is in perfect condition.

You might have the same problem, just more severe. My old neighbor had the same type of problem (rough idles). He replaced his TB immediately, and it ran like new. That would be my guess. My just .02, flame away if need be.


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## LampyB (Apr 2, 2007)

itskohler said:


> I've had an awkward idle "shudder" for 2 months. When I took it (still under warranty), they thought it was a vacuum leak as well. Low and behold, that wasn't the problem. I honestly think it got WORSE with them tinkering in the engine bay. They then said its the TB and told me that the item wasn't under warranty because I hadn't gone to them for the 40k mile tune up and went to a dealer alternative instead. Who is a certified dealer altertnative from VAG (f-ing crazy right? :screwy I haven't replaced it yet. I'm waiting for some other things for my car to roll in so I know for a fact that the TB is in perfect condition.
> 
> You might have the same problem, just more severe. My old neighbor had the same type of problem (rough idles). He replaced his TB immediately, and it ran like new. That would be my guess. My just .02, flame away if need be.



i'm hoping the TB doesn't need to be replaced, it's an expensive part. i picked up the wrong coolant temp sensor, i need the gray one (not green). green is too large for the wiring harness. i trusted the parts guy at vw would get it right, but oh well. i also came across a crimped hose tonight on my intake. resolving this may be easier than i thought....(fingers crossed) :sly:


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## itskohler (Jan 7, 2011)

I really hope, for your sake, that the hose is the root of all your problems. The 300-400 dollar ball park for a part isn't too bad, but labor will be a killer. I was quoted just under 800. :banghead:


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## thygreyt (Jun 7, 2009)

itskohler said:


> I really hope, for your sake, that the hose is the root of all your problems. The 300-400 dollar ball park for a part isn't too bad, but labor will be a killer. I was quoted just under 800. :banghead:


just get it out of a junk yard!!!


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## LampyB (Apr 2, 2007)

so a TB isn't a simple install?? i was thinking it would just be some bolts and removal of the intake...


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## itskohler (Jan 7, 2011)

I honestly have no clue how complex, or easy, the install procedure is. Its dealer prices and we ALL know how they make their prices. 

I've been looking at local junkyards for an MKV, and I cant find any up here (looking for that 6 speed mt  )


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## pennsydubbin (Mar 3, 2010)

Throttle body disassembly and install is really easy. Take off the CAI then you just unscrew those 4 bolts that you see then take off that top hose and there's one more on the bottom :thumbup:

I can't believe you were quoted $7XX.XX to replace the trottle body. That's sad that the dealer would charge $300-400 for a 15-20 minute job.


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## nothing-leaves-stock (Mar 1, 2005)

its easy.
-take intake tube off(stock or CAI)
-un click TB connector
-remove 2 heater coolant hoses
-4 screws holding the TB to the intake manifold.
-smash old TB on the ground in 1000's of pieces.
-install new one in reverse order
-DO NOT START the car, just turn key on, let sit for 20-30 sec. to adapte
-you MAY have to use a vag-com to adapt. most don't tho


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## itskohler (Jan 7, 2011)

Ya, all dealerships are like that though. They have that stupid ****ing book that gives the prices and times that a certain mechanic can complete the job. Then it goes by the competencies of the mechanic. The higher the skill level of the mechanic, the more they charge. So if the book says 3 hours, thats what they charge even though its way less than that. *******s.

I'm looking at replacing it myself and saying **** the warranty.


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## pennsydubbin (Mar 3, 2010)

Yea just do it yourself man.


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## LampyB (Apr 2, 2007)

If it turns out to be a bad TB i will need to pick this part up from you as well Jimmy!


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## pennsydubbin (Mar 3, 2010)

LampyB said:


> If it turns out to be a bad TB i will need to pick this part up from you as well Jimmy!


I'll be here if you need it :thumbup:


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## tay272 (Aug 22, 2007)

I wish we had some decent junk yards around our area that actually have VWs that arent Mk3 or below. Mk4s are even hard to find in most around my area so forget about any 
Mk5s.


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## elf911 (Jul 27, 2007)

LampyB said:


> 08 Rabbit - 93 Oct. Tune - CAI - 66K Miles
> 
> Alright, I'm at a loss as to what's causing my problem. Experiencing the following symptoms:
> 
> ...


Any access to a Vag-Com? If not check the forum and find someone near you with one to do a quick scan on your car (Boston is a big city so it should be easy to find someone) My battery was crap after 5 years (approx 54k miles) and changing it helped startup alot. I also had a problem with a EVAP relay that caused my care to studder violently but only after a fill up. If your ever in NYC let me know and we can check it out :beer:


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## IJSTROK (Oct 2, 2007)

I noticed today my fans kept running when I would turn my car off for much longer than normal (10-15 minutes after shutoff). Scanned it with vagcom and I got P0116 for the coolant temp sensor. I didn't have any other symptoms like the ones you are having though, no rough idle or even a CEL. I'll be replacing the sensor later this evening. 

Just to verify this is the coolant temp sensor correct?


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## LampyB (Apr 2, 2007)

yep, that's the coolant temp. sensor. make sure the car is 100% cool when doing it though, and take off the coolant reservoir cap prior as well to relieve any pressure in the system, otherwise coolant will spray everywhere when the sensor is removed.


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## LampyB (Apr 2, 2007)

UPDATE: i replaced the coolant temp. sensor and my extremely rough idle, as well as the startup issues were fixed. that damn little bugger caused quite a bit of havoc! after replacing the sensor i put a temporary fix on my crimped intake hose by putting a ring clamp around the hose to force it to maintain shape. worked well until the replacement stock plastic hose arrives from Pennsydubbin (Jimmy). i'm just glad it was a cheap fix and not a bad TB or Catalytic Converter. 

my idle still has a minor fluctuation though, hardly noticeable. i will be swapping out the maf to see if it helps in the next couple of days.


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## DerekH (Sep 4, 2010)

LampyB said:


> UPDATE: i replaced the coolant temp. sensor and my extremely rough idle, as well as the startup issues were fixed. that damn little bugger caused quite a bit of havoc! after replacing the sensor i put a temporary fix on my crimped intake hose by putting a ring clamp around the hose to force it to maintain shape. worked well until the replacement stock plastic hose arrives from Pennsydubbin (Jimmy). i'm just glad it was a cheap fix and not a bad TB or Catalytic Converter.
> 
> my idle still has a minor fluctuation though, hardly noticeable. i will be swapping out the maf to see if it helps in the next couple of days.


I'm pretty sure the minor fluctuation is normal, my car has had it since i got it. Lemme know if swapping the maf fixes it though. Would be nice to see it gone.


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## halbwissen (Jul 20, 2001)

DerekH said:


> I'm pretty sure the minor fluctuation is normal, my car has had it since i got it. Lemme know if swapping the maf fixes it though. Would be nice to see it gone.


Yeah, my idle has a little flux too.
Not a big deal. I call it character.

You should clean your MAF before you replace it.
Get some CRC MAF cleaner.
I clean mine every 10k with the CRC cleaner.
That's something I've been doing for year s now on all my MAF equipped VWs.


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## seanmcd72 (May 14, 2008)

LampyB said:


> cutting in and out is a small symptom that i'm experiencing, like i said above when holding down the gas pedal consistently to hold a low speed of say 10mph. the car stutters when i do this, like the throttle is going in and out. when i press down normally with adequate pressure during acceleration everything's fine though.


 I've had this happen to me a handful of times. My car (2008 manual trans Rabbit, now with 54K) idles fine and doesn't stall, but once in a blue moon I notice this little stumble happen _exactly_ as you describe.


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