Hello all . Been away for a bit but I finally got myself another bug after my last one was written of in an accident several years back . So I now have a 2001 turbo beetle automatic . This car was pretty much heading for the scrap yard when I got it . It had been sitting on a farm for 5 years . I've been working hard on this car , replacing the brakes , the timing belt and water pump , some of the rusty panels , etc. . So now I'm at the point where I'm driving this car daily , for 3 days now . I do have a check engine lamp illuminated on the dash but so far it's only been for a SAI issue that I still need to tackle . I found this car when giving it gas it tends to bog down for a few seconds then seems to pick up , and it gets worse the more I push it . I did have it stall out on me a couple times but after replacing the fuel pump it hasn't done that anymore . I've put new spark plugs in , changed the oil , and run through a couple tanks of gas so far , and it's not getting any better . I'm hoping someone has some ideas for me to check out .
1.8T engine bogs down under heavier acceleration
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Typical issues on a high milage, neglected 1.8T! 
I’ve been on a many years journey; making my 1.8T run the best it can and in the early stages of my troubleshooting, this hesitation was my first foray into troubleshooting turbo drivability issues. My problem, was persistent and a head scratcher without even any trouble codes, to five one a clue as to what was going on!
Here was my process here:
www.newbeetle.org
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I’ve been on a many years journey; making my 1.8T run the best it can and in the early stages of my troubleshooting, this hesitation was my first foray into troubleshooting turbo drivability issues. My problem, was persistent and a head scratcher without even any trouble codes, to five one a clue as to what was going on!
Here was my process here:
diverter valves: stock motor; APR aftermarket vs. stock...
Hey, am having issues at the top end of the rpm range on my 02 1.8T turbos S (180HP AWP); I have about 70K and have never replaced the DV. I have taken it out; inspected it and tried the "test" as noted in the lined .pdf below. When you are getting at the top end of the power curve; the turbo...
www.newbeetle.org
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So, the first thing i would check is the diverter vale, which can bind, warp from heat and the n75 which controls the waste-gate on the turbo charger. Both of these parts are crucial for correct boost actuation and top turbo performance, functionality; oddly they can stop working as they should (soft failure) oddly, not throw any codes!
Review my old thread and we can discuss things further!
Review my old thread and we can discuss things further!
Thank you , I will look into this in the next couple of days . I previously had a 2003 GTI where it was also nothing but diagnose running issues . On that engine , I think every single vacuum hose has cracked and was leaking . After a year of working on it I finally got it running great , which meant I had to turn around and sell it .So, the first thing i would check is the diverter vale, which can bind, warp from heat and the n75 which controls the waste-gate on the turbo charger. Both of these parts are crucial for correct boost actuation and top turbo performance, functionality; oddly they can stop working as they should (soft failure) oddly, not throw any codes!
Review my old thread and we can discuss things further!
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#9 Wastegate Bypass Regulator Valve -N75-
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Volkswagen Workshop Manuals > New Beetle GLS L4-1.8L Turbo (AWV) (2001) > Powertrain Management > Fuel Delivery and Air Induction > Turbocharger > Air Bypass Valve, Turbocharger > Component Information > Locations
New Beetle GLS L4-1.8L Turbo (AWV) (2001) > Volkswagen Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Turbocharger > Air Bypass Valve, Turbocharger > Component Information > Locations
workshop-manuals.com
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Testing and inspection:
Volkswagen Workshop Manuals > New Beetle GLS L4-1.8L Turbo (AWV) (2001) > Powertrain Management > Fuel Delivery and Air Induction > Turbocharger > Wastegate > Component Information > Testing and Inspection > With Manufacturer's Scan Tool > Page 5214
New Beetle GLS L4-1.8L Turbo (AWV) (2001) > Volkswagen Workshop Manuals > Powertrain Management > Fuel Delivery and Air Induction > Turbocharger > Wastegate > Component Information > Testing and Inspection > With Manufacturer's Scan Tool > Page 5214
workshop-manuals.com
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Ok, solid diagnostics, confirmed BAD part found and new DV installed! oem Kayser or the latest VNE oe recommended. FCPEuro, is a great supplier; for failure prone parts like the DV’s, free shipping and lifetime warranty!
Porsche VW Diverter Valve - VNE 4008172
06A145710N
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oem Kayser or the latest VNE oe recommended. FCPEuro, is a great supplier; for failure prone parts like the DV’s, free shipping and lifetime warranty! Porsche VW Diverter Valve - VNE 4008172
06A145710N
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Boost is more stable but still has moments of hesitation before the boost kicks in . No fuel trim issues but I do have some misfire codes (P0300 and P0301) . I had already installed new plugs so I swapped the #1 and #4 coils and cleared the codes . I will see what comes back . The issues are not consistent , as at times the car runs great , but it still mostly acts up when pushing the engine a little harder . Like accelerating from a stop .
Very busy at work this week , so I just ordered in the N75 and installed it . Did not correct my concern . What I am finding is that if I go about half throttle it works fine . If I go a little more it starts bucking and cutting out . If I let off and then go back on it will usually smooth out . If I floor the accelerator it will buck and sputter for a few seconds then take off . Sometimes when it's acting up the CEL light starts flashing but will go out . The codes it sets are misfire codes , which originally I thought were part of the cause but now I think it's being caused by the concern . Otherwise no codes .
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What scan tool are you using and can it read live data? I would be looking at the maf readings and things, like the fuel trims. as well. Normal fuel trim ranges; are typically + or - 10 %.
Fuel Trim Info - Ross-Tech Wiki
www.ross-tech.net/vag-com/advertising/DiagnosingA_MAF_TechTip.pdf
You mentioned, that you replaced the fuel pump; at one point, what brand was it, did you replace the fuel filter, plus the fuel pressure regulator at the same time and have you confirmed, the fuel pressure is in spec?
Fuel Trim Info - Ross-Tech Wiki
www.ross-tech.net/vag-com/advertising/DiagnosingA_MAF_TechTip.pdf
You mentioned, that you replaced the fuel pump; at one point, what brand was it, did you replace the fuel filter, plus the fuel pressure regulator at the same time and have you confirmed, the fuel pressure is in spec?
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Volkswagen Workshop Manuals > New Beetle GLS L4-1.8L Turbo (AWV) (2001) > Powertrain Management > Fuel Delivery and Air Induction > Fuel Pressure > System Information > Specifications > Pressure, Vacuum and Temperature Specifications (workshop-manuals.com)
Volkswagen Workshop Manuals > New Beetle GLS L4-1.8L Turbo (AWV) (2001) > Maintenance > Tune-up and Engine Performance Checks > Fuel Pressure > System Information > Specifications > Pressure, Vacuum and Temperature Specifications > Page 1775 (workshop-manuals.com)
Volkswagen Workshop Manuals > New Beetle GLS L4-1.8L Turbo (AWV) (2001) > Maintenance > Tune-up and Engine Performance Checks > Fuel Pressure > System Information > Specifications > Pressure, Vacuum and Temperature Specifications > Page 1775 (workshop-manuals.com)
I'm using a Snap On scan tool . It can do live feed . I will have to a road test and see where the sensors are reading . As far as the fuel pump goes , I just grabbed one out of a freshly killed beetle at the local pick n pull . The MAF was one thing I was thinking of but I'm not getting any codes from it . I realize not all issues will set codes but I would hope stuff like a MAF would at least set an out of range code . I'm still wondering if I have coil issues as well .
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When, things are such that trouble codes; do not provides any clues, as to what is going on, then targeted testing, live data can provides data in real time, that may help diagnose things. Hopefully, a process if elimination; can help narrow things down.
As to the used “fresh kill” fuel pump; used parts, can “save money” initially but with these cars getting into the 15-20+ years old , you maybe installing incorrect or old worn out parts. For crucial performing parts; say, for fuel delivery and ignition or turbo related, high quality oem new parts are recommended. Installing potentially more used parts is a gamble; as you could just be swapping out old defective or worn parts; for more of the same, making diagnosis, even more of a challenge.
That is where testing comes in and double checking the used parts are performing well or are the incorrect parts, is always a good idea.
If the fuel pump is bad; stick with high quality oem Bosch or VDO, for new replacements.
As to the used “fresh kill” fuel pump; used parts, can “save money” initially but with these cars getting into the 15-20+ years old , you maybe installing incorrect or old worn out parts. For crucial performing parts; say, for fuel delivery and ignition or turbo related, high quality oem new parts are recommended. Installing potentially more used parts is a gamble; as you could just be swapping out old defective or worn parts; for more of the same, making diagnosis, even more of a challenge.
That is where testing comes in and double checking the used parts are performing well or are the incorrect parts, is always a good idea.
If the fuel pump is bad; stick with high quality oem Bosch or VDO, for new replacements.
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I totally get that, too; so, then, backing up their use with confirming they are the correct parts for your car and testing their performance, is to spec, as they should be, is going to be some extra work required, as part of the installation of used parts route. Just another extra step and another level of a unknown variable; into, your diagnostics process.
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Okay so out of curiosity I slapped on another throttle body I had and it made no difference . So tonight I finally got a chance to go for a drive with the scan tool on . My fuel trims are good (long term was at .8 for most of the drive , ended up going to 2.1 , short term varied between -2 to +3) . Found MAF reading was 5.75 g/s at idle all the way up to 75g/S at full throttle . The one thing that did catch my eye is when the car would act up the throttle position would jump up to 100% .
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