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Assuming your 1.8T is rated @ 150 HP:

. Assuming this test is done at or near sea-level, the peak output of the sensor in g/s should be roughly 80% of the rated horsepower of the engine.

150 x .80 = 120 G/S

So, 75 G/S is low; I would double check and do the test, as per the Ross Tech .pdf, which is maxing out the air flow the engine is capable of by running it until the governor kicks in. This would be "WOT" wide open throttle in 2nd gear; which might be harder to do with a automatic, unless you can somehow, get it to stay in second?
 

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Discussion Starter · #24 ·
Just threw on the other throttle body on a hunch . I did clean out the throttle body but didn't do an alignment procedure . I don't believe that is the issue anyways as it made no change to the issue at all . Yes I had the A/C on while I did that road test (it's 30°C/86°F today) . And as for altitude I live in Calgary Alberta in Canada at the foothills of the Rocky Mountains . We are at 1045m/3428ft above sea level . Now the throttle position is what has me curious . Not sure if the concern is messing up the readings on the scan tool or if the throttle body valve really is opening up to 100% when it's acting up .
 

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Are there any current trouble codes?

The maf does seem on the low side; is it possible, to a “WOT” staying in second gear? Do you have the 6 speed Tiptronic auto trans?


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I’m a bit concerned about all these used parts; you have thrown into the mix, as to if they are correct or performing to spec?

Lately, we have had some members throw on used parts; as a way to test for bad parts but then, the parts ended up being wrong, causing even more problems.


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Discussion Starter · #27 ·
I understand your concern over used parts . Not everything I have put on was used . The diverter and N75 valves I put on were new . I am only using used parts to keep costs down . I do my best to try and verify I am using the correct parts .
 

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Ok, sounds good; if we can get a solid test and readings on the maf, that would be good, then we could cross that off the list of possible issues.


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Discussion Starter · #29 ·
So I think I had a brain fart when I did the fuel pump . I totally forgot about the fuel filter . This car sat on a farm for five years and it's a fairly high mileage vehicle (356,000kms/228200m) . I've been sitting here thinking that maybe the fuel pump is bad again , but something didn't seem right . The car did not have this issue when I bought it and drove it to my shop , which was from an hour outside of my city . I changed the pump originally because the car started to stall out when driving exactly like my GTI did when that fuel pump went . After putting in the fuel pump the stalling went away but then this issue started up shortly after . I will put in a new filter tomorrow and see if that makes a difference .
 

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You might pop up the seat and remove the fuel pump cover, take a photo and post it or tell us, what brand, what part # is listed on it. The last time, I did my fuel pump; I went with VDO and then, replaced the fuel filter as well but then, a bit later, ordered a new Bosch pressure regulator and noted, a DEFINITE, improvement in performance. You just have to assume, all these 15-20+ year old parts are potentially original, worn, tired and not up to top performance levels or in "soft failure" modes (working but not at top levels they should be). Everything you installed, especially the used stuff; should be tested and confirmed correct, performing to spec. Did you ever do a fuel pressure test?
 

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Discussion Starter · #33 ·
Here's the thing , I'm not in the U.S. , I'm in Canada . So I got a new fuel filter onto the car and test drove it . It ran great , with no issues - for about 5 mins or so . Then the concern showed up again . I'm thinking I'm on track with the fuel system . I'm going to look into getting a fuel pressure gauge here soon , and will go from there .
 

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Discussion Starter · #35 ·
That's what I'm thinking is getting one from Princess Auto or even Amazon . Getting one off the tool trucks would be way too expensive and I wouldn't get my money's worth out of it .
 

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Do they rent tools; at the auto parts stores, in Canada? There is the cheap tools; from Princess Auto, right (like our Harbor Freight)?
I’ve used the harbor freight grade Chinese stuff; can be sub standard, they can be inaccurate and even had the gauge pointers, literally fall off.

I would try to rent a set from a auto parts store or friend. I’m a fan of quality tools; i buy allot of used pro grade stuff at flea markets, garage sales and pawn shops for cheap, even vintage tools can be excellent, some hardly were ever used much.

Even a Actron brand gauge, sold at most auto parts stores; would probably be better then a Princess Auto Cheapie from China.



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Discussion Starter · #37 ·
I will look at getting one here soon . I agree with getting quality tools . Although it may not seem like it from my posts I am actually a professional dealership tech , been with GM for 18 years . I'll admit I don't know as much as I would like about the 1.8T engine . And I am getting frustrated over this as I figure I should be smart enough to get this . I have been very busy over the last couple of days so I haven't been able to do much . But I have noticed a few things . First , after replacing the fuel filter the car drove good until it warmed up , and it will do that every time it's cold . To me it's acting like it's running out of fuel . I grabbed another fuel pump from the wrecker under a parts warranty just to verify . There was no difference . This to me is a good sign that it's not the fuel pump as it's not very likely to get two faulty pumps doing the exact same thing in a row . Not impossible , just not likely . And until I get a pressure gauge I'm kinda just on hold for now .
 

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Well, we are here to help; if we can continue a back and forth dialogue, start doing a process of elimination, we should be able to narrow things down, find the cause of the problems.

The 1.8T can be a real challenge to diagnose; especially, a high milage one, that has been neglected and with lots of old original parts, which are typically in “soft failure “ mode.

We need solid data, to confirm things; rule them out, mark off the list, this data needs to be results of proper testing. The testing, following the factory vw manual specs and procedures; should help with assumptions, random parts swaps and get down to solid data, to “pass/fall” status, on a list of suspected bad or weak parts. Then, we can make solid progress; moving down the list of possible typical failure modes we see all the time with these era VW’s and in particular, the 1.8T, which can be a challenge to diagnose, get running at its top performing level.

Nothing should be assumed and that is why verified data, from testing can, remove confusion and bring clarity, to your diagnostic process.

The whole fuel system needs tested; the service manual, has a series of tests, running pressure, dead head, residual and testing the fuel pressure regulator on the fuel rail as well.


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Discussion Starter · #39 ·
I have been rolling this around in my head lately . My next thing I was thinking of checking is the regulator . To do that though I will need to get a pressure gauge . Hopefully sooner than later .
 

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Do auto parts stores in Canada; offer auto tools and things like fuel pressure test kits, for rent? This is very common here in the USA; which is nice, if you don’t have a specific needed tool and helps get the job done. As to buying a fuel pressure tester; pretty much every auto parts store here; has them in stock for sale but they are usually Actron or other mid to lower quality brands. OTC seems to be popular with the more pro level testing tools and then, there are the usual suspects; on the high $ tool trucks, snapon, mac, matco, cornwell, etc.

A good USA made brand; which has been a oem to many of the tool truck brands is LANG tools and for example, a leak down tester i have from them, is identical to the one sold on the Snapon truck, for a fraction of their rebranded price.




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