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Discussion Starter #1
I had a DTC for the rear O2 heater circut a couple of weeks prior,
Ordered the part & also had to do a heater core R&R at the same time. That took the best part of 4 days.

After the heater core R&R the car started and ran, took it out on the hiway & it started to cut out, bog down at times no response to the peddle. Made it home and now will kick over & die, can't get it to run.

I changed out the sensor & found the wires bare as they entered the sensor, there's the short.

Now when I turn the key to the on position I hear the fuel pump prime the system then stop but I also hear a ticking cycling sound comming from the throttle body, this cycles 11 times, back & forth. Sound like an old cooking timmer being wound, but fainter.

DTC codes are P1543 , and the O2 heater / sensor in-op.

I'm debating buying vag-com but $250 right now is tuff.

Anyone have a shorted OD heater circut or know about the ticking from the TB. Seems to be cycling to set it's self but can't.

I have a Chiltons repair manual comming but it's on back order.

Anyone with a Vag-com in the 08861 zip code area ?

Thanks.

bob

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Discussion Starter #2
Bit the bullet & bought Vag-Com should have it in a couple of days.

I removed the TB, It was a little dirty so i cleaned that with some TB cleaner & bolted it back up and turned on the Ignition to see if it would continue to cycle thru what ever it is it's doing. The 2nd time I turned the ignition it was still cycling. I can see the throttle plate opening & closing. Does anyone know what this is doing ? Is it common or a sign that maybe something else is wrong , like a fried ecu from the down stream O2 sensor shorting out ?

Also noticed I'll need some new vac hoses, nothing major but they need to be replaced, 132K miles now on it.

bob
 

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Does anyone know what this is doing ? Is it common or a sign that maybe something else is wrong , like a fried ecu from the down stream O2 sensor shorting out ?
This is normal. It is what is called "throttle body adaption" where the ECU learns where the throttle closed position is. It not normally done every time you start the car. It can be initiated with VAG-COM or by switching the key to "run" without starting the engine, which seems to be how you are getting it. It should take something like 10 or 15 seconds to complete. If it keeps running you may have an internal problem with the throttle body that isn't allowing it to run through its full range.
 

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Discussion Starter #4
thanks Red... I started to pull the plastic cover off the gears on the Tb but stopped. The throttle opens ~ 1/4 way then cycles between there & closed position. your time frame is about right, cycles 11 times or so then stops.

Prior to the car was running well although this is the 2nd coil pack I installed over the last 3 years. MPGs just under 29 on the last fill up.

First start right after heater core install went ok, idled , took it out on the rd then it started cutting out, bogging down. I hadn;t changed out the O2 sensor at that time so really don't know if I screwed that up.

Vag-Comn due i9n the am but wont be home till after work.

Thanks again for the input.

bob
 

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A couple of things that come to mind, the harness for the throttle body is close to the heater hoses. Any chance the harness may have been damaged when the heater core was changed? Second, did any coolant get on the wire harness and maybe short something out?

The rear O2 sensor is only used to check the catalytic converter function. It isn't used to control the engine at all so it isn't causing your problem.
 

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squirreljuice
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I know with the 1.8T engines, if you short your O2 sensors you fry something in the ECU that causes the car to start and run but the throttle wont work. Perhaps something like this happened to you. I cant say though because I know nothing about the 2.0 engines and their systems. Just thought I would throw that out there for consideration...


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Discussion Starter #7
@ red... No damage to harness or spillage. filled the core prior to install & capped off stubs.

@ squirreljuice ... someone else pointed me to a thread on adding a ground as a fix for a short in the O2 heater circut causing a problem in the ecu.

Vag-Com is due this morning so I'll have more info late this afternoon.

I also manually opened the throttle, some where I read this may cause problems, going to pull the cover to the gears on the TB
after I see what the vag-com tells me. Another thread had one open & something about a gear that slipped out some how.

I'm seeing rebuildt or new TB's from $99 to $245. Any one have problems with aftermarket or rebuild TB's ?

bob
 

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Discussion Starter #8
The Vag-Vom arrived today & The throttle body adaptation was a success I couldn't start the car because I want a new TB gasket & I ordered some silicone vac hose that will be here later this week.

I thought I created a log file of the first scan but seems I didn't. There were four codes, 2 for the o2 2 for the TbB1 was the angle being out of spec , forget what the other was. I cleared all DTC's & did the Tb adaptation, switched off the car then turned it back to the on position and instead of the cycling sound there was just a steady buzzing from the same location. Vag-Com tells me no faults so we'll see what happens from here, will keep everyone posted.
 

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Discussion Starter #9
It lives.... After reassembly of the TB the bug started right up. Let it idle for some time while I played with the Vag-Com. Took it for a quick spin about town with no noticeable problems.

I was able to real time graph air intake temp, coolant temp, rpm, and O2 sensor during the drive. Before I finished the O2 sensor voltage went to 0 so it looks like I'll be buying the upstream O2.

It sat long enough ideling so that the fans kicked on breifly which was a concern because they didn't come on that I noticed last it was running.

I have no CEL on with these DTC's.

Below is the log of the last scan I did tonight, cpl of faults but she runs again.

Thursday,21,November,2013,16:28:01:49413
VCDS -- Windows Based VAG/VAS Emulator
VCDS Version: 12.12.0.0
Data version: 20130910


Mileage: Repair Order: 1st read after fix



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--------------------------------------------------------------------------------


Address 01: Engine Labels: 06A-906-018-AEG.lbl
Control Module Part Number: 06A 906 018 AB
Component and/or Version: MOTRONIC M5.9.2 HS V10
Software Coding: 00040
Work Shop Code: WSC 08261
VCID: 62C5A0F7EE8EB40EE27-4B32
2 Faults Found:

17951 - Angle Sensor 1 for Throttle Actuator (G187)
P1543 - 35-10 - Signal too Small - Intermittent
16518 - Oxygen (Lambda) Sensor B1 S1
P0134 - 35-10 - No Activity - Intermittent

Readiness: 0110 1101
 

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Discussion Starter #10
Replaced the upstream O2 this morning in driveway @ 30 degs. & windy. Took longer than I expected with that funky harness shield & the fact that the sensor looked to be cross threaded. A real bear to get off, more I twisted the harder it got to turn. Ran car for about 10 min prior to extraction which helped.

I used this for work friday with the in-op O2, knew it was bad as i used 1/4 tank for about 78 miles.

With the new sensor in had a cpl of misses on cylinder 1 ( using vag-com ), then the vag com went south for some reason keeps telling me it sees the dongle but won't let me save the info in setup.
I have no DTC's, or CEL light & car runs as strong as ever. Hope to be up over 30 mpg on the next fill up.

Removed O2 looked pretty beat up, will take some readings & inspect it further.

Thanks for all your help.

Bob.
 

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Discussion Starter #11
I popped the p0420 Catalyst System Efficiency Below Threshold. That had showed up a cpl days ago but it never set the CEL . Car runs good although I'm loosing PS fluid with no apparent leaks.

I've read elsewhere that driving around in 4th gear 3 to 3.5K RPMs ( the itilian tune up). to cook off any carbon build up on the cat matrix .

The vag-com allowed me to connect tonight when I got home, that's something.

bob
 

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Verify engine operating temperature, should be around 205F/96C.

Also check and report back fuel trim values at warm idle and steady cruise 45-55 MPH.

P0420 is an industry wide problem, usually mean the cat efficiency is below 95%. Also note that the 2.0l had a lot of cat related problems as well.

Suggest you make sure the engine temp is correct and the fuel delivery/control system is in good shape before you worry too much about the P0420 code.

Just "manage" the P0420 code for now.
 

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Discussion Starter #13
Will do. I have noticed the temp from 95c up to 105.5c+, this was at idle.

Drove it into to work this morning but didn't have the vag-com hooked up,too cold too early & running late. The CEL cleared itself
& 30 miles into brooklyn ny car ran well. Running it friday with the bad O2 gave me ~ 16MPG hoping for 30+ on the next fill up.

When I can get a handle on the vag-com I'll post the results.

bob
 

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Discussion Starter #14
Verify engine operating temperature, should be around 205F/96C.

did a run cpl day ago temped look to stay at 90c to 91.5C

Also check and report back fuel trim values at warm idle and steady cruise 45-55 MPH.
where do i find them using the vag-com. what block do i monitor ? I was into the menu option under advanced something or other section. Saw thrott; angle, coolant temp etc but no " fuel trim " .

Thanks for any info .


Bob
 

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did a run cpl day ago temped look to stay at 90c to 91.5C



where do i find them using the vag-com. what block do i monitor ? I was into the menu option under advanced something or other section. Saw thrott; angle, coolant temp etc but no " fuel trim " .

Thanks for any info .


Bob
Temp could be a bit cool, not sure where you live or what your outside temps were. May not be an issue, but you should keep an eye on the temps.

Not sure where LTFT values are in VAG-Com/VCDS as I do not use this much, so do not recall where it is located.
 

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Discussion Starter #16
I'm in NJ, outside temps where about 35f. I'll have to play with the vag-com.
Thanks again.

Bob
 

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Discussion Starter #18
Thanks red... will have to see what I have. First fill up after the new O2's gave me just over 26 mpg, less than I hoped for.


bob.
 

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Discussion Starter #19
Ok, just did a quick trip & logged some parameters that the article red linked above. Did the MAF to redline : @5160 RPM MAF : 67.36 g/s
@6280 RPM MAF : 55.76 g/s

article stated " Your peak airflow should be roughly 0.80 times your horsepower if you are close to sea level. So, if you have a stock 150 hp 1.8T, expect around 120 g/s. If you see significantly less than that, you MAF may be on the way out. "

My intake air mass topped out at 67.36 g/s, 1k rpm below redline..

I've had the car a cpl of years now & don't know if the MAF has been replaced. Anyone have any input on the above numbers ?

I'll have to go back & check fuel trims to see what they are, when you re-run the graph after logging it the graph is a little vauge on which reading is which, thay atre not labled just parameters used to measure what ever input it is.

Still popping the p0420. ironic #.

0.80 * 114hp ==> 91.2 g/s
 

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Here is a calculator to get the expected MAF reading for the engine and atmospheric conditions:

D-tips

When I checked mine earlier this year I got 79 g/s @ 4400 rpm and the calculator value was 71 g/s at the time.

Your low reading could just be a dirty MAF. The fuel trim will help confirm this if it is off on the + side.
 
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