# Exhaust Leak Symptoms?



## burkechrs1 (Dec 1, 2008)

What would be the symptoms if I had a small exhaust leak either at the turbo to exhaust manifold or somewhere after the turbo but before the primary 02 sensor?
I have an exhaust leak but I never though anything of it I just ignored it knowing in a couple months I'm getting a new tb exhaust. Recently someone mentioned that some of the other minor problems my car has could be related.
Thanks for the help.


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## Dub-Nub (Sep 27, 2005)

well what are the other minor problems?
You will be able to hear an exhaust leak, especially at cold start with a/c off.


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## burkechrs1 (Dec 1, 2008)

*Re: (Dub-Nub)*

At cold start its a huge exhaust leak. I'm pretty sure its my sai pump leaking at the rivets because it shuts up once the cold start is done. But I don't throw a code cuz of my tune. 
Some of my problems include:
-Horrible Gas Mileage (275miles/tank)
-Idle dips ~150 rpm randomly then comes back up
-Hesistation when i roll onto the gas, especially in 1st gear but happens in all gears
-A slight ticking noise but it isnt valves or my injectors; gets slightly louder under boost
No boost leaks and no vacuum leaks were found with a boost leak test...


_Modified by burkechrs1 at 6:12 PM 11-11-2009_


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## burkechrs1 (Dec 1, 2008)

*Re: Exhaust Leak Symptoms? (burkechrs1)*

anyone else?


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## burkechrs1 (Dec 1, 2008)

*Re: Exhaust Leak Symptoms? (burkechrs1)*

pleeeaaassseeee?
I've been doing some research on google but I would like your guy's knowledge too..


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## skywalkersgti (Mar 27, 2007)

*Re: Exhaust Leak Symptoms? (burkechrs1)*

unplug o2 sensor. car will dump fuel. look around for fuel comming out of the turbo-mani/mani to head/dp to turbo(most likely) just get the car on ramps/stands and take a look with a good flash light. have someone else start the car(not in gear). and take a gander.hope this helps


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## burkechrs1 (Dec 1, 2008)

*Re: Exhaust Leak Symptoms? (skywalkersgti)*

alrighty. i would see black smoke come out of any leaks right? should i have a friend cover the tail pipe so there is more back pressure?


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## skywalkersgti (Mar 27, 2007)

*Re: Exhaust Leak Symptoms? (burkechrs1)*

get the car on ramps. and listen for a leak. NASA does not need to be involved. listen. and feel around. youll find it.


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## Dub-Nub (Sep 27, 2005)

as a last resort you can use seafoam in the intake system to trace exhaust leaks


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## theirlaw (Nov 27, 2005)

*Re: (burkechrs1)*

If you have any luck diagnosing your issue can you please update this post? I've been typically getting 450-500 kilometers a tank (about 275 miles) and my idle dips as you describe every so often. Although I I relieved the hesitation you describe somewhat by replacing my IAT sensor and cleaning my throttle body, occasionally it still occurs. My piping also holds boost as I've used a compressor to determine if there are leaks.


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## skywalkersgti (Mar 27, 2007)

*Re: (theirlaw)*

scan the car for actual codes.


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## burkechrs1 (Dec 1, 2008)

*Re: (theirlaw)*


_Quote, originally posted by *theirlaw* »_If you have any luck diagnosing your issue can you please update this post? I've been typically getting 450-500 kilometers a tank (about 275 miles) and my idle dips as you describe every so often. Although I I relieved the hesitation you describe somewhat by replacing my IAT sensor and cleaning my throttle body, occasionally it still occurs. My piping also holds boost as I've used a compressor to determine if there are leaks.

will do.


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## fobyulous (Oct 7, 2007)

*Re: (burkechrs1)*

updates?


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## first9t! (Jul 13, 2009)

*Re: (fobyulous)*

im in the same boat, bad gas millage, idle dips, sometime hesitates on the gas... still cant figure it out..


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## skywalkersgti (Mar 27, 2007)

*Re: (first9t!)*

scan your cars.


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## Buschwick (Feb 12, 2007)

*FV-QR*


_Quote, originally posted by *Dub-Nub* »_as a last resort you can use seafoam in the intake system to trace exhaust leaks











http://****************.com/smile/emthup.gif That is the best way to find an exhaust leak IMO. Plus you get a clean intake, valves, and cylinders!
If you do that the leaks will be so obvious you don't even need to look for them. They will all show their face.


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## biggoodjohn (Dec 7, 2006)

*Re: Exhaust Leak Symptoms? (burkechrs1)*

I have a 2004 1.8t. just had and exhaust leak fixed. crack was just below the flex pipe at a weak jointed area and before the catalytic convertor. to replace it is one piece from exhaust manifold to past the catalytic conv. Mad Hatter Muffler shop in Columbus OH put in a new flex joint and section of pipe for $100. it took about an hour and a half and eliminated a weak spot in the exhaust.


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## dmach18t (Aug 19, 2009)

*Re: Exhaust Leak Symptoms? (biggoodjohn)*

Some of my problems include:
-Horrible Gas Mileage (275miles/tank)
-Idle dips ~150 rpm randomly then comes back up
-Hesistation when i roll onto the gas, especially in 1st gear but happens in all gears
-A slight ticking noise but it isnt valves or my injectors; gets slightly louder under boost
I am having the same exact issues with my car. And the ticking noise is slightly louder when the engine is cold. I have noticed these issues a few weeks after I installed my FMIC. I think I may have leaks. BUt can the leaks cause a ticking noise?.Which is my biggest isuue I think is the ticking noise. It just sound like my turbo is goin bad or sumthin


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## dmach18t (Aug 19, 2009)

*Re: Exhaust Leak Symptoms? (dmach18t)*

BUMP^^^^^^


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## fobyulous (Oct 7, 2007)

*Re: Exhaust Leak Symptoms? (dmach18t)*

TTT 
still trying to figure out if those symptoms are caused by exhaust leak...I have the exact symptoms described by OP


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## dmach18t (Aug 19, 2009)

*Re: Exhaust Leak Symptoms? (fobyulous)*

seems like alot of ppl are having the same issues but no one seems to know what it is not even my local dealer......Which blows big D#*k......


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## McBee (Aug 11, 2006)

*Re: Exhaust Leak Symptoms? (dmach18t)*

Yes, some of those are symptoms of an exhaust leak. 
Just seafoam it instead of guessing.


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## first9t! (Jul 13, 2009)

*Re: Exhaust Leak Symptoms? (McBee)*


_Quote, originally posted by *McBee* »_Yes, some of those are symptoms of an exhaust leak. 
Just seafoam it instead of guessing.

true that.. seafoam works great for finding leaks!


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## clarkma5 (Mar 2, 2002)

Very interesting, I've had a rather sudden drop in my fuel economy in the last 6 months (I'd say I used to get 25 city/30 highway and now it's more like 22 city/27 highway, so pretty much 3 MPG across the board). Occasional fuel smell in the cabin, particularly while the engine is warming, occasional dips in the idle. I had some roll-on throttle hesitation as well, which was helped a LOT by a fuel filter replacement, but seems to be coming back a bit. Overall there's definitely something there but it's hard to tell what exactly!

I also had the mysterious "under-1/4-tank-constant-revs-light-load throttle-cutting-out" issue happen to me on a few occasions...which is one of those fun problems that people seem to spend a lot of money not fixing (fuel pumps, relays, throttle position sensors, MAFs, O2 sensors; you name it, people have replaced 'em)

I've been eyeing fuel injector seals as the cause on the recommendation of a friend...I do have a very small amount of residue around the base of the injectors, though I haven't seen any wetness or actual squirting of fuel from the seals.

Overall this exhaust leak upstream of the O2 sensor phenomenon sounds like a promising place to look...I've been investigating it as a fuel system issue but an airflow differential between what the O2 sensor reads and what the engine is actually getting would also explain a lot of these things. Will be looking at this!


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## soupercoupe (Jan 30, 2015)

burkechrs1 said:


> At cold start its a huge exhaust leak. I'm pretty sure its my sai pump leaking at the rivets because it shuts up once the cold start is done. But I don't throw a code cuz of my tune.
> Some of my problems include:
> -Horrible Gas Mileage (275miles/tank)
> -Idle dips ~150 rpm randomly then comes back up
> ...


You seemed to answer your own question? The Secondary Air Injection system comes on during a cold start for about 65 seconds then shuts off so you will hear an exhaust for that time frame if it is in fact a leak in the SAI system.
I have the same problem, I havent taken it apart yet to see what part of the SAI system is leaking, but from research its either the Combi valve, or rivets on air pump, or cracked air ouput hose from pump to Combi valve, any else have any insight on this, I know its late response but better than no respnse at all.


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## clarkma5 (Mar 2, 2002)

Bump on this old one.

I continue to have similar symptoms in my stock 2004 1.8T...fuel economy now averaging down to about 23 MPG (for a decade, it was consistently 27-28, then started sliding in the last 6-12 months; I have a full spreadsheet of all my fillups and associated mileage going back to 2005), I have occasional dips in idle and it seems like my power is just a little below where it should be. I have scanned the car many times and not gotten a single code that relates to these issues. I have done the following in the last year or so, covering a range of mileage from ~80k to ~100k. I know the car's entire history because I am the original owner, plus I've done most of the work on it myself.

-Pressurized the exhaust system, found leaks at the turbo-downpipe connection, and re-tightened those bolts (this seems to have helped, but as I re-check these bolts they are still tight and don't leak, but I still have some symptoms)
-Replaced all the fuel injector seals (due to a mild but noticeable fuel smell in the car during warmup; did this at the same time as the turbo-downpipe bolt tightening. I think the bolt tightening is what addressed the smell, as the original injector seals were still fine)
-Cleaned the MAF and throttle body and did a throttle body alignment (no major difference either way)
-Started replacing the fuel filter every 10k miles (definitely helped the first time I did a change with throttle response and so on, not so big of a difference subsequently)
-Pulled the fuel pump to clean the intake screen and check the tank for sediment (cleaned what there was to clean, but the tank and screen were pretty clean. Also did this to address the "1/4 tank throttle-cutout" issue, and it didn't seem to make it better or worse. It was the first time the fuel pump had been touched.)
-Cleaned my K&N filter every 10k miles (I've been doing this since I installed it at 60k; before that it was paper ones every 20k)
-Seafoamed the intake system, yes there were a couple little exhaust leaks. I addressed a couple while I did my PCV system (see below)
-New spark plugs (old ones looked reasonable)
-Replaced PCV system with 034Motorsport silicone hoses and check valve, at same time as new OEM DV, PRV (hockey puck), APR turbo inlet pipe, and plenty of fresh hose clamps. The old hoses didn't have any noticeable tears or cracks, maybe the old valves were failing or there were leaks at the clamps? This one really seems to have helped the full-operating-temperature, "highway" sort of economy, the gas gauge just doesn't budge on the highway...this was already where the car was performing best but it seems to have gotten better. However the city driving and overall average fuel economy is still low, perhaps even lower than before.
-Just had 034Motorsport do a clutch and flywheel with clutch slave cylinder and new input shaft/axle output seals and bearings. They had to remove the transaxle completely to do the job; the transaxle feels good now and so does the clutch, in fact the whole drivetrain is smoother, but the engine has developed something of a rattle at low revs? It almost sounds like maybe a heatshield was left slightly loose but maybe I'm getting more noise from an exacerbated exhaust leak? After a decent start to my latest tank (half of which was before the clutch/flywheel and half of which was after), my latest average MPG over a whole tank was just 21 MPG (eek!) and while I did give it some gas to test the new clutch and everything, I also got a good amount of time doing highway cruising and puttering around town. I would expect an average of at least 26 MPG from that sort of tank, not 21.

I also unhooked the battery completely after the clutch/transaxle job (itself just a couple weeks after the PCV system) to reset the ECU. It seems to run better but if anything my fuel economy got a little bit worse again! Would perhaps be consistent to an engine that's still hiding some issues.

So TL;DR, I've tried a lot of things, and have experienced some relief predominantly when I address exhaust leaks and the PCV system. I think I have to continue to address leaks in other parts of the exhaust system. This seems to be one of those issues that is decentralized and has multiple factors contributing to it. The car won't throw a code as it's not too far off from its operating window and the ECU is compensating, but it's compensating in a way that hurts fuel economy and a little bit of power (though response right now feels quite good).

I'm hoping I can go through the exhaust system for the price of fasteners and gaskets, maybe hangers (?), and fix my leaks. I'm running out of ideas beyond that point.


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## suffocatemymind (Dec 10, 2007)

clarkma5 said:


> Bump on this old one.
> 
> I continue to have similar symptoms in my stock 2004 1.8T...fuel economy now averaging down to about 23 MPG (for a decade, it was consistently 27-28, then started sliding in the last 6-12 months; I have a full spreadsheet of all my fillups and associated mileage going back to 2005), I have occasional dips in idle and it seems like my power is just a little below where it should be. I have scanned the car many times and not gotten a single code that relates to these issues. I have done the following in the last year or so, covering a range of mileage from ~80k to ~100k. I know the car's entire history because I am the original owner, plus I've done most of the work on it myself.
> 
> ...


Have you ever replaced the primary O2 sensor? Have you pressure tested the intake for boost/vac leaks? Sounds like you have it buttoned up otherwise.


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## clarkma5 (Mar 2, 2002)

I've never touched either O2 sensor and have only cleaned the MAF, otherwise I haven't done anything to any sensors. Based on what I'm reading, I'm inclined to think it's hard for my car to run the way it's running if the sensors are bad, as it really does run pretty good. I've pressure tested the intake and think I addressed what I found with the recent PCV hose replacement job. Which is why I'm turning my attention to the exhaust.

Another reason I'm turning my attention to the exhaust is when I notice my fuel economy dipping. Get it on the highway at 70+ MPH? I'm getting the same 30+ MPG I've always gotten. Run it hard (or at least harder) over a mountain road? Surprisingly economical! It's when the car is just puttering around at lower revs, lower stress, lower throttle that my gas gauge plunges quickly. It SEEMS like it could be exhaust-leak-based, as such small leaks would surely close up with thermal expansion and open up when things get cool, yes? At least, this is the best I've been able to figure.

My next step is to get the car up in the air and seafoam it, looking carefully for exhaust leaks from the turbo back to the muffler, and see what I find. I intend to note any areas and get seals and fasteners and hangers as required to rebuild the stock exhaust tight as can be. (I'd ponder getting a 50-state 2.5" Neuspeed downpipe and CARB-legal catback, but I am intending to sell the car reasonably soon.)


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## suffocatemymind (Dec 10, 2007)

Have you pressure tested the intake for boost/vac leaks? Do you have VAGCOM to confirm fuel trims, etc.? Remember, the gremlins aren't always what you expect them to be...


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## clarkma5 (Mar 2, 2002)

Sorry I didn't quite finish my thought when I posted it.

Yes I have pressure tested the intake system, before I did my PCV system and TIP, and found basically nothing in terms of leaks; that job probably did what it did because it addressed aging diverter and PCV valves. It was the seafoaming I did later on that pointed out a couple leaks that really were starting on the exhaust side of the turbo, at least one of which I've addressed with hose clamps while doing the PCV work. Yes I have a VAGCOM, yes I check codes (there are none), yes I have logged all sorts of fuel trims and sensor data and not come up with anything particularly strange. I also forgot to add that I did the SAI pump rivet fix (which didn't seem to change performance or economy, just how healthy the car sounds during warmup).

I logged this data a few months back:

https://dl.dropboxusercontent.com/u/29521325/2015_01-16-Run1Graph.png
https://dl.dropboxusercontent.com/u/29521325/2015_01-16-Run2Graph.png
https://dl.dropboxusercontent.com/u/29521325/2015_01-16-Run3Graph.png
https://dl.dropboxusercontent.com/u/29521325/2015_01-16-Run4Graph.png


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## clarkma5 (Mar 2, 2002)

Well, I may have gotten ahead of myself with the fuel economy improvement from the PCV work. It didn't get worse, and it does seem better at highway speeds? But I'm still pulling the same ~24ish MPG average I have been for months (maybe it's more like 24-25 than 23-24?), vs. the 27-28 I got for ten years.

When I did the PCV system and DV and TIP, the engine didn't run so good on the first couple start ups. I used my VAGCOM to see the car has P0302 and P0300 fault codes (no warning lights; both misfire codes, intermittent, on cylinder #2 and "ECU cannot detect cylinder", respectively). I figured this was due to the ECU having to re-adjust its fueling due to the changes I had made. I cleared the codes and called it a day. The car ran slightly better than it had before.

I just checked for codes again and got the same two codes, still no warning light. The engine really does run fine outside of very small occasional idle bounces, the fuel economy thing, and feeling like it is perhaps a few HP down from its best (though that's really hard to tell, could just be how much extra grip I've put into the chassis via modding over the years...makes the engine feel relatively less powerful, due to having more grip, control, and braking).

I haven't yet seafoamed to check for leaks in the exhaust system and at the O2 sensors, and I should re-do another intake system pressure test, but I will do those this afternoon.

I am wondering if it could be A) the most recent spark plugs I installed (I went for NGK copper cores instead of the nicer OEM NGKs, and immediately noticed how much worse the electrode looked in terms of manufacturing quality...I also gapped the spark plugs into the .028-.030 range, based on recommendations from this forum, instead of the OEM .032) or B) degrading ignition coils? The ignition coils were all replaced under recall roughly 50k miles ago. The original ones never had any problems.

Overall I'm really scratching my head over this whole thing.

P.S. I checked my compression recently and it was easily within spec and very even across all 4 cylinders.


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## clarkma5 (Mar 2, 2002)

So I seafoamed to look for leaks in the exhaust and checked the intake. The intake/PCV stuff is tight. The exhaust had tiny leaks at the exhaust-turbo connection and at the back end of the center muffler.

I decided to take it to a local, well-reviewed muffler shop to have them look at it. The owner was adamant that he couldn't feel any leaks that could explain what I was trying to figure out, and to leave it all alone. After walking through all the things I'd already done, their results, and my misfire codes, he latched onto the misfire codes and told me to check my ignition wires.

Well, going by this to check the actual wires that lead to the coilpacks, my wires are fine (wire sheathing not cracked): http://www.uspmotorsports.com/downloads/vw.tb.97-04-02.pdf

The consensus online seems to be that coil packs are to blame? http://www.ecstuning.com/Volkswagen-Golf_IV--1.8T/Engine/Ignition/ES2561321/

However, then there is this technical service bulletin from 2009: http://workshop-manuals.com/volkswa...engine_controls_dtcs_p0300-p0304/p0420/p0441/

I'm inclined to think that's not the issue though because this has developed along with the fuel economy drop, give or take. I think I will be trying new coils and plugs first and foremost.


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## clarkma5 (Mar 2, 2002)

Update on my end: new coilpacks and OEM platinum NGKs arrived and I swapped them all out. First impression is that throttle perhaps picks up a little bit cleaner, power might be better, but hard to tell if it's real or placebo effect. Real test will be how fuel economy responds. Will post here.

Sorry for hijacking this thread, but thought it might be helpful to document my troubleshooting process. In my case, it seems that suspecting an exhaust leak was not the cause of my issues FWIW.


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## rstolz (Jun 16, 2009)

injector duty cycle.

N249 functioning properly?

if mileage is plummeting when puttering around, that would suggest not turbo related. Still might be worth pulling off the turbo and inspecting it for cracks or other damage. If it's all plugged up, or the bearing is shot, or fins are hitting the walls, it could be causing an excessive restriction in the exhaust flow. That could go away once it gets enough pressure behind it to get it spinning. that's a long shot, and not really likely, but it is possible.

Did you compare your old plugs to a plug chart? were they burning clean and even, caked in anything?

how about a compression test. Marginally low compression can be masked under boost, but may be apparent under low-no boost times.


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## clarkma5 (Mar 2, 2002)

Interesting ideas.

The turbo spools cleanly and does not surge, I don't think anything I'm experiencing fits the symptoms of a failing N249 or the turbo issues you mention, but it's a good consideration for others reading this thread. If my fuel economy does not return with this current tank I will get diagnostic on the N249, but so far on this tank it seems to have done the trick (I've been watching my fuel gauge like a hawk in different driving situations; suddenly with new coils and around town driving, my gauge is staying put and I'm on track to get the 45-miles-per-eighth-tank that I always consistently got for the first ten years I owned the car...that fell to a wobbly 30-35 in the previous 6-8 months).

Spark plugs looked good and normal, albeit with only a couple thousand miles on them (I did the copper NGKs at 100k miles, was disappointed with the quality of the electrodes vs. the platinum NGKs in terms of how nicely machined/deburred they looked, so happily went back to the platinum NGKs included in the ECS coils & plugs kit. Checked gaps and they are consistent at .030. Previously I had gapped my plugs to .032 all the time, which is OEM; last time I did plugs with the coppers I tried a tighter gap that was more like .028 on the coppers. May have been part of the issue, even though my fuel economy problems started well before I installed those plugs.)

Compression test a couple months ago was 155 psi across the board, extremely consistent. Within VW's spec for new engines, albeit on the lower end, but I did the test when the engine had cooled to the point of being lukewarm and temperature is a major factor in compression tests. People who test hotter get higher compression. So I'm quite confident my compression is good.


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## suffocatemymind (Dec 10, 2007)

Winter blend fuel also plays a sizable role in fuel economy


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## clarkma5 (Mar 2, 2002)

I have been keeping fuel economy records on a tank-by-tank basis rigorously since 2005. I do not see any consistent evidence of winter fuel blends causing dips in fuel economy that are significant compared to other driving habits/random variability.

I offer this exhibit for the perusal of others:










I find that long trips, periods where the car is driven less/more, city vs. highway driving, and track use are the major independent variables that impact fuel economy. Winter/summer doesn't seem to make much impact.

I'm identifying the area starting around the beginning of 2014 as the time when my economy started declining; several very long road trips (WA to CA and back twice, WA to Montana and back) bolstered the overall average.


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## suffocatemymind (Dec 10, 2007)

Hmm. Winter-blended fuel where I live definitely makes a difference. GL


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## clarkma5 (Mar 2, 2002)

Well, the car has spent its whole life in California or Washington state (Seattle area), where winters are milder. Could be a factor. Still think the winter/summer fuel blend fuel economy thing is far overblown. I just can't see it causing more than maybe a 1 MPG drop. Not 4-5.

As for my fuel economy with the new coilpacks and spark plugs, the car got about 150 highway miles this weekend. Getting that 45 miles-per-eighth-tank I used to always get, and that was with my boyfriend driving a lot of that with a lead foot (I tend to get better economy than other drivers due to my conservation of momentum), significant headwinds, and so on. When I used to drive to college and back years ago in similar conditions, that was the sort of economy I would get. Still need to see how it averages out over a full tank of standard mixed driving, but considering that before I couldn't get over 40 miles per tick even with gentle highway driving, it's a significant step. It's likely a multi-variable problem, and at some point I have to accept that an 11 year old car isn't going to get the same economy as it did when it was newer. I'll be happy if I get most of the way back to where I was at. First 150 miles points to having maybe achieved that.


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## Jadiel18 (Dec 16, 2012)

pictures over words :thumbup:












my car ran fine with this gasket... it would pull hard lose boost then pick up again specially in 1st gear & my fuel economy suffered bad (gasket between ex mani & turbo) replaced mine and its about 28-30+ mpg now

oh btw i could barely hear the exhaust leak but it was there specially on cold start


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## clarkma5 (Mar 2, 2002)

That's where my pinhole leak is located. If I want more economy, maybe that's my next step.

The nice thing with my coilpacks replaced is that, for the last several months, I would watch my gas gauge plummet during cold starts. Now it holds steady. Before the car seemed to lose most of its economy during warmup and short trips, and do reasonably well when warmed up and especially on the highway. And I'm sitting exactly at 3/4 tank with 90 miles on my trip, which is my consistent 45-per-eighth I used to always get. Feeling optimistic!


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## CD155MX (Dec 18, 2007)

Very helpful thread. Any new updates on this?


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## Samfelly (Jun 21, 2016)

Please, I have this same problem with the symptoms you mentioned. How did go about it? I mean, have you really solved it?


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## Samfelly (Jun 21, 2016)

Please, help. I have the same problem with my car also.


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## CD155MX (Dec 18, 2007)

Bringing this back from the dead.......

I had been having some of the same issues as described by clarkman. I did a seafoam this weekend and found a sizable exhaust leak. Hopefully fixing this helps with my mileage. 

Photos in my thread here:
http://forums.vwvortex.com/showthread.php?7125523-Jazz-Blue-20th-Anniversary-No-2062&p=103157201&viewfull=1#post103157201


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