# 1.8 rough idle



## Brendan81 (Jul 18, 2005)

my 01 1.8 gti has a strange problem, it runs rough at idle and sometimes actually stalls. The RPMs bounce from 800 to 1000k while while at a stop light/ stop sign and this is when it sometimes stalls, I'm getting no check engine light which is the strange thing, can anyone shed any light on this? 
thanks


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## vgasbrkdrms1 (Jun 23, 2009)

why is this happening to everyone!!


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## Yosh_Cupra (Jun 28, 2008)

Slight vacuum leak, bad MAF, check the FAQ...


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## VDUB Modder (Nov 30, 2005)

hey man ive been dealing with this for the longest time... Do you have the 01"? because that what i have and every time i hear bout this its the 99.5 to 01". Its never the 02" and up. Just recently I ran a test just by unplugging my maf so the A/F runs off the presets.. When the ecu finally adjusts to its presets the problem you and i are having goes away with no more of that annoying rpm ish. I feel like its some kind of bug in the ecu of those specific years... I could be wrong cuz thats a bold statement, but there is still no solution to the prob so who knows. Im eventually goen to build my head, crossing my fingers it does something to change that.. 

ps i have a brand new maf


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## VDUB Modder (Nov 30, 2005)

Yosh_Cupra said:


> Slight vacuum leak, bad MAF, check the FAQ...


 that what ive tested for and some but everything was good


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## So Fast its EVIL (Dec 15, 2006)

Brendan81 said:


> my 01 1.8 gti has a strange problem, it runs rough at idle and sometimes actually stalls. The RPMs bounce from 800 to 1000k while while at a stop light/ stop sign and this is when it sometimes stalls, I'm getting no check engine light which is the strange thing, can anyone shed any light on this?
> thanks


 FAK...this is EXACTLY what i'm getting. I have a 03 20th AE. I haven't checked the MAF or vac lines yet (we've had a lot of rain). 

How would i know if the MAF is bad? Can I clean it??


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## So Fast its EVIL (Dec 15, 2006)

OK, I'm HOPING i've solved this issue. I got some electrical contact cleaner and cleaned the MAF connector pins and the throttle body connector (to be safe) and plugged it back in and voila....rock steady idle (well, as steady as a VW is ever going to be...lol). If the problem resurfaces I will take the actual MAF element out to clean but for now it seems to be working fine.


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## So Fast its EVIL (Dec 15, 2006)

So Fast its EVIL said:


> OK, I'm HOPING i've solved this issue. I got some electrical contact cleaner and cleaned the MAF connector pins and the throttle body connector (to be safe) and plugged it back in and voila....rock steady idle (well, as steady as a VW is ever going to be...lol). If the problem resurfaces I will take the actual MAF element out to clean but for now it seems to be working fine.


 UPDATE: Well, it came back...not as severe as before but, its back. Any idea's? Could it be an idle air controller issue??


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## chaveezy (Jan 31, 2010)

I've got this rough idle deal to! Mine's an '02 but was built late '01, I just resealed all my intake tubing and fixed a couple things (added thread sealant to the hardware in my ATP 3" inlet), I thought this was the problem but nope. Replaced the plugs, was thinking coil packs but it runs good above idle and never has thrown any CEL's for misfire. Plus, my coil packs are stamped 4/09 so they were just recently replaced. 

It could be MAF, as I haven't checked that, but I don't really think there is a check for that is there? 

Hmm.. One guy on here says his coil pack wiring harness had some cracks in the grounding wires causing misfire issues but again, no CEL or anything and doesn't really seem like a misfire.. Ah, who knows..  :banghead:


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## VW/1.8T (Sep 8, 2010)

try a crankcase breather valve. i had the same problem and i threw one in and it disappered. as of now its still fixed.


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## groggory (Apr 21, 2003)

at the very least, check for vacuum leaks and exhaust leaks. Preferably pressure test the system.


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## rickross667 (May 12, 2009)

same problem here..i have an 01 also..ive checked for vac leaks..im have maestro so im running mafless..new hitatchi coil packs and a new coil pack harness..rpms still bounce at idle.. 

i dont understand it


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## BassNotes (Mar 16, 2005)

Time for VAG-com.


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## racin2redline (Sep 25, 2008)

could it possibly a bad coolant temp sensor? :sly: just a thought


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## Imola Yellow GTi (Oct 27, 2000)

My idles at 800 while waiting at the traffic light and it dips down to 500 and then bounces back to 800. 

I do have a minor rip in one of the PCV hoses. That should be replaced with the 034 breather hose kit this weekend. *Would a rip in one of the PCV hose cause this?*


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## chaveezy (Jan 31, 2010)

I don't see this to be a crankcase ventilation issue, as my vaccum reading is consistent -20psi, plus, I found that at cold start it runs great, nice and steady idle (1200rpm then drops to 800rpm), once the car is warmed up, it starts to do the jumping idle. 

What would VAG-COM be able to do for us if we're not getting any CEL? I'm thinking about buying one of the CAN-BUS USB systems from Ross-Tech but I'm still undecided.


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## groggory (Apr 21, 2003)

Small rip in PCV hose will cause that and a drop in gas mileage (from personal experience) 

Only get the CAN interface if you plan on throwin it on MKV+ cars. Our MK4's are HEX, so that interface is kinda overkill. 

To everyone who's checked their vac, are they actually running pressure tests? Or taking an easy way out. Our vacuum system is much more finicky that people give it credit. I had worn out hoses under the IntakeMani that were super hard to find, but fixed lots of my issues. A pressure test is the only real way to do this.


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## Pg-Getta1.8 (Jun 27, 2006)

get vag and realign the Throttle Body


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## transient_analysis (Jan 28, 2003)

groggory said:


> A pressure test is the only real way to do this.


taking a piece of vacuum tubing, sticking one end in your ear, and then using the other one to fish around all the joints of the PVC system is also a good way to find leaks while the engine is running


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## bmp20th03 (Sep 11, 2009)

Make sure the throttle body is clean and adapt it. Also like other people of said adapt the throttle body with vag com and check your fuel trim in vag com to see if you have a vac leak.


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## chaveezy (Jan 31, 2010)

What exactly does adapting the throttle body do?


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## VDub1.8chick (Oct 30, 2010)

I am having a very similar issue with my 03 1.8T. I have had vaccum lines tested and replaced, throttle body cleaned, coils & plugs replaced, MAF, O2 sensor....please see post from today.... 

http://forums.vwvortex.com/showthre...3200-later-shop-still-baffled&highlight=$3200 

They still can't figure out what the problem is.


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## Henni (May 14, 2003)

I see the rough idle that my car has everyone else does also. 

booo....


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## Imola Yellow GTi (Oct 27, 2000)

VDub1.8chick said:


> I am having a very similar issue with my 03 1.8T. I have had vaccum lines tested and replaced, throttle body cleaned, coils & plugs replaced, MAF, O2 sensor....please see post from today....
> 
> http://forums.vwvortex.com/showthre...3200-later-shop-still-baffled&highlight=$3200
> 
> They still can't figure out what the problem is.


 That leaves... coil pack harness, SAI pump, and combi valve.


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## Henni (May 14, 2003)

I replaced my coil pack wiring harness. It did make a HUGE difference.


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## Imola Yellow GTi (Oct 27, 2000)

Really wish VAG would of used better 'packaging' of the coil pack harness. If they did, a majority of these issues would not occur.


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## Zneith (Jan 4, 2010)

I've had this problem before as well and part of the problem was coilpacks. Check the wiring harness and the coilpacks themselves. Next, my asr and traction light were on and it put my car into a 'backup' program letting me run no more than -5psi. What i had to do was get carb cleaner, clean out the throttle body REALLY well, take a cue tip and clean around the butterfly valve. Let that sit, do it again. I did this about 5 times to be sure its all clean, then started the car and let it idle for like 5-10 minutes. No more rough or bouncy idle, no more lights and i was ready to rock. The one major thing that you need to do after this is a throttle body alignment. I forget what block, just need to search. Goodluck:thumbup:


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## codergfx (Jan 11, 2009)

My car was doing same thing when water got into the ECU connector, Dont ask how.


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## skateakoston (Oct 15, 2009)

Zneith said:


> I've had this problem before as well and part of the problem was coilpacks. Check the wiring harness and the coilpacks themselves. Next, my asr and traction light were on and it put my car into a 'backup' program letting me run no more than -5psi. What i had to do was get carb cleaner, clean out the throttle body REALLY well, take a cue tip and clean around the butterfly valve. Let that sit, do it again. I did this about 5 times to be sure its all clean, then started the car and let it idle for like 5-10 minutes. No more rough or bouncy idle, no more lights and i was ready to rock. The one major thing that you need to do after this is a throttle body alignment. I forget what block, just need to search. Goodluck:thumbup:



i know this is old but was the idle problem with your gt3071r and eurodyne set up? because i am running the same setup and have idle fluctuation between 200 rpms very randomly..


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