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I normally drive an 02 TDI Jetta, but recently bid on an online auction for a 2004 Passat with AWM 1.8t gas engine.
It was advertised as running, driving, stopping condition. Got it for $750.00 which i thought was great. Drove to Phoenix to pick it up and it had a bad miss at idle which dissapears when you give it gas.

I have ross tech Vag Com that i use with my TDI so i hooked it up and measured blocks showing misses in the engine and there were several on each cylinder.
This led me to believe that the coilpacks where probably bad so i went and got brand new NGK plugs and coilpacks, installed them, and then it popped a code for
Pressure Drop between Turbo and Throttle Valve (check D.V.!)

This led me to the diverter valve. Found it and then clamped off the small hose with channel locks - started car and idle was still rough. Unclamped the channel locks and nothing changed on the idle so i am under the assumption now that the diverter valve probably isnt the problem.

Next i got my mapp gas torch and passed it around every hose i could find looking for a vacuum leak and the engine never changed idle with the torch head anywhere near any hose.

The only thing i can physically see is this 90 degree fitting is cracked. What is this, what does it do, and will this cause bad idle?

Thanks in advance for any help

Anthony awm.jpg
 

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Discussion Starter #2
Forgot to mention that i also unplugged the MAF to see if anything changed and it didn't change anything with the idle either.

Anthony
 

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̶T̶h̶a̶t̶ ̶l̶o̶o̶k̶s̶ ̶l̶i̶k̶e̶ ̶p̶a̶r̶t̶ ̶o̶f̶ ̶t̶h̶e̶ ̶P̶C̶V̶ ̶p̶i̶p̶i̶n̶g̶ and if it is cracked it can cause a vacuum leak which is the most likely cause of the bad idle. There are many, many threads about the PCV system and vacuum leaks since the plastic bits tend to get brittle with age and crack. There are also various check valves and vacuum jet pumps that can fail, etc. That engine looks pretty clean so hopefully there won't be many issues. One problem with servicing these parts is that it's easy to break parts trying to remove them to get at the ones that are already leaking.

034 motor sports sells a silicone hose version of a PCV replacement system. That is a good option if you plan to keep the car for a while. Otherwise a smoke test can help pin-point vacuum leaks but probably won't help much with the check valves, etc.

edited post since info was wrong...
 

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Regarding those two hard pipes:
>one is part of the PCV system (top pipe, I believe)
>the other is the air output of the SAIP (secondary air injection pump, generically the "smog pump") and connects to the combi valve at the rear of the engine. The combi valve has a silver-colored top and a vacuum line connection (blue in my picture) and is easily visible. I think this is the bottom pipe (things vary by year, and my Passat is gone).

If the elbow in question is for your SAIP, it won't cause a vacuum leak or any other performance issue. It might cause a P0401 code if it's leaking a lot. The SAIP is a high pressure electric fan that runs 100 seconds on a cold start to help warm up the cats to improve emissions. It's located more or less under the right headlight.

1.8T overview labeled.jpg
 

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how many miles on that bad boy? any service records? As to the "stopping" condition mentioned in the first post, that is a common problem with the 1.8Ts which are "sludge" prone, under capacity with oil volume, and oil lines directly above turbo.Just dirty by nature, first thing you need to do is address the oil issue, once that is corrected and maintained everything else will fall into place, hopefull no damage has been done if engine has been starved for oil. as to tubes in pick all rubber is easy to get/buy metal tube need to be removed and cleaned out ,you will see that are probably clogged or damn near clogged. Tons of write up here on 1.8s oil issues and better yet excellant advice and solutions, The other thing when you replaced coilpacks was there any oil down inside where they reside....if so ,you new ones will be toast soon enough. Last but least evaluate TB age/wear.....
 

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On the AWM, if you are getting that pressure drop, it is a massive leak. go over everything from the throttle body to the turbo. I know, sounds obvious. It could be a hole in the intercooler (behind the driver foglight), loose intercooler to intake hose, the hose from DV to intercooler crossover pipe, or even the Bleeder valve under the intake. The last one not as likely, but worth looking into.

That broken hose is the SAIP feed going to the kombi valve. You should also be getting a code for "Secondary air, incorrect flow". Speaking of, what codes did you pull, exactly?
 
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