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y2k Reflex Beetle 1.8t
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Discussion Starter #1
Mornin dubbers.
2000 1.8t aph.
Drove good 5 days ago but my mileage has been poor (23mpg). Filled it with gas, drove 12 miles, shut it down, restarted it 20 minutes later, drove a mile, parked it. 5 days later it starts then stalls. If I "save" it by depressing the gas pedal about 1/8 I can get it to stay running but then it cycles between 1000 and 2000 rpm very consistently. It was not throwing any codes at that time. I've since cleared the ecu in case it was using bad values from memory, hoping it would run enough to relearn / adjust but that didn't help.
I hooked up my homemade soup can pressure tester to check for vac leaks and I hear a very familiar hissing from the pcv neck area down below the #3 fuel injector / behind the sai pump. I had to change out the plastic pcv tube in my last 1.8t aph about 6 months ago as it was cracked and falling apart. Im guessing ill be doing the same on this one. BUT my last one just ran poorly because of it, but it ran, not like this issue.
So I pulled the plugs because I needed to anyway, they were fresh 1000 miles ago and look fine. Coil packs new at that time also. No other vac leaks that I can hear and the hoses I can see / touch look good (had replaced several 1000 miles ago also.) Air filter is good, sai pump ran and it's hoses were intact and seated well.
So now I'm thinking:
Cam position sensor?
Throttle body / position sensor?
MAF?
Crank angle sensor?
Fuel pump / filter / bad fuel? ( the cycling seems too consistent for these)

Like I said, no trouble codes. : /
If anyone's seen similar or has opinions on focusing my diagnosis I'm much obliged. I do have a vcds hexv2 which I barely understand, seems like it could help but without codes and not running I'm flying blind at my knowledge level.
Thanks in advance for your input.
 

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I had the same problem when I first bought my 1.8t awp beetle. It was the high voltage fuse panel on top of battery and battery, I paid $500 USD for the car and replaced those 2 things( battery, High voltage fuse panel),in the engine bay. Your RPM fluctuations may be due to low voltage from the alternator to the high voltage fuse panel and/battery. Check accessory belt and the charging system, then move on to Crank Position, Cam ,Knock sensors and go from there.


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y2k Reflex Beetle 1.8t
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Discussion Starter #3
High voltage fuse panel "looks" Ok, and the battery is under a year old and holding 12.6v after all the cranking. Accessory belt was replaced last year and looks fine. I'll keep this suggestion in mind and dig deeper but I decided to remedy this split crankcase breather tube first. I have it out and am ordering a replacement. I wish I could find a metal one.
248923
15682775319702017194286.jpg
 

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High voltage fuse panel "looks" Ok, and the battery is under a year old and holding 12.6v after all the cranking. Accessory belt was replaced last year and looks fine. I'll keep this suggestion in mind and dig deeper but I decided to remedy this split crankcase breather tube first. I have it out and am ordering a replacement. I wish I could find a metal one. View attachment 248923 View attachment 248923
Also replaced my breather system with PCV delete kit from ECSTuning. Com, as well as SAI/evap delete but my car is now tuned. So probably


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y2k Reflex Beetle 1.8t
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Discussion Starter #6
Thanks guys.
I'm tuned also but it was by previous owner so I don't know the specifics (grr). That cycling business said vac issue to me but my other (not tuned) ran steady with virtually the same issue. I'll get that done and see where I stand. I did find that the metal diverter valve' s screw on metal sleeve where the large hose attaches was not screwed on tight so I remedied that but it still wouldn't idle. Didn't even realize that was removable, glad i caught it. Parts should arrive early next week, will report afterwards, thanks again.
Oh ps just in case, 2.0 coil upgrade, adjustable metal bov, 3" turbo back / high flow cat. Decided back then I'll be sticking with this car and will be upgrading as things fail. Mentioned the mods in case they may relate to current issue. And i like that we can "like" posts now!
 

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Well, it can take some time and learning curve; to get your 1.8T running right, especially if it was neglected over the years. The Ross Tech VCDS, is crucial; in learning to diagnose your VW and it allows, a number of testing and output tests, that can really help things. Looking for boost leaks, is definitely; a great first step, to get things running well; keep in mind, there are many parts, that regulate boost and other things, that get old, don't perform as they should and cause problems, in this case they can be in a "soft failure" mode, which means, they can technically "work" but not at the level they need to, for the car to run correctly.

The first step in troubleshooting a VW with VCDS; is always, to run a "autoscan" and see what trouble codes come up. Then post those codes up and we can start from there.

It sounds like your already ordered pcv parts; however, there are some aftermarket silicone hoses and upgraded pcv, related parts, that can really improve, the failure prone stock PCV system.

The PCV can be replaced with a aftermarket billet aluminum version; the hoses can be upgraded to silicone and base of the hose, comes with a billet aluminum replacement version.

034 Motorsports; offers a "late" and "early" version; you might contact them and see what would be correct for your particular application:


As to the stalling issue and overall bad running; as noted, a full auto scan in VCDS, would be a good place to start. You might go over all the various things you have done; many aftermarket parts, like the adjustable diverter valves, can be problematic and you might not even know it. Here is a thread; where I was dealing with boost issues and hesitation; this might be helpful, to read over and start testing some thing:


Post up those codes; we can start working down, the possible issues and you can start testing things, to find the cause of the problems. Thanks! :)
 

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y2k Reflex Beetle 1.8t
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83 Posts
Discussion Starter #8
Solved. It's the maf sensor. Quick diagnostic is to simply unplug it and see if it runs. Unplugged mine and it started and idled.
Thanks as always, everyone.
Billymade, those billet breather tubes look AWESOME but I have the redheaded stepchild APH engine and the part # doesn't match up. : / Meanwhile I'm sure the one I removed was not original (No Part # on it, no green o-ring) so if anyone's intending on not needing to ever replace that again, go billet if you can!
As an aside, I had first checked for codes using my vcar igate2 and it came up clean. My vcds showed 08016 (if I'm remembering correctly) almost certainly due to the high flow cat mod. There was no cel.
I was surprised that was the only code but I'm thinking it didn't have time to produce any codes, so on the docket was to try and start it and keep it running until it might trip one.
Anyway, thanks again.
 

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Good to hear; you found the problem, stick with oem Bosch maf sensors, they have a unique hot film sensor and other cheaper aftermarket versions don't, thus cannot read as accurately.

 

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As for the pcv silicone hose kits; you might contact 034 Motorsports about compatibility or just try them out, to see if they fit (note: the early/late versions; they offer)..In general most 1.8T beetle's have the same parts but you never know, until you try (most aftermarket silicone and other parts are geared towards the jetta/golf).
 

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y2k Reflex Beetle 1.8t
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Discussion Starter #11
I bought a genuine vag maf, installed, runs great. I had already ordered and installed the breather tube, maybe next time I'll call 034, thanks for your and everyones input as always.

Stealership note: $250 + $53 core, not in stock. VW Parts Vortex $168, delivered to same dealership or +$7 delivered to my door in 2 days. Between that and not selling my replacement keys anymore I'd debadge my car if it wasn't so obviously a vw. I'd think they'd care about having near classics on the road, it speaks well of the brand.
 

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Sounds good: that is great a new maf solved your problem? Next time, consider buying a oem Bosch part; many VW sensors are made by Bosch and are the same, as the ones from the vw dealer for less (just no vw/audi logo on them).

You can look up Bosch parts and sensors by application, then search online for the best prices:


As for keys/key fo s; check out tunemyeuro or sidewinderkey websites online.
 
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