VW T3: Common O2 sensor (wiring) issue 

Thomas EXOVCDS no injection = no problems ... when the damn wire won't snap inside the carb :( still mad

Did the acid get it out?

Thomas EXOVCDS i removed some casting flash off to see what happens / if it reacts with the material . Well .... it didn't leave any. I will try compressed air and then 1 go injection 2 buy a new carb

Nothing but you :P

About 4 years ago, I bought a Passat. Your videos taught me the things I needed to learn in a perfect way. Once you mailed me some stickers, which I put on my Passat (30V) GLX wagon. I sold that car a few years back and didn't remove the stickers. The baby with the headphones on is still alive today. Cracked after 4 ish years in the Utah sun, then now in Maine sun and winters. It's still there making a mark on the world. :D Now - If you have a moment to review this diatribe, I would be very grateful for any suggestions... I have been chasing a system lean code on a Mk5 GLI BPY / FSI for ... 2 years. I have replaced or otherwise positively made sure the following parts are in proper working order. Front PCV / crankcase vent valve = replaced several times. With and without check. Current valve has check (and the rear tube as well). Diverter valve = I have this on Auto order from Amazon they fail so much. Rear vent valve tube = With and without the check valve. Current rear tube has valve. Rear main seal was replaced as was the front seal and all other seals. Valve cover - yes the entire thing. HPFP STFT = +5.3 ~ +2.1 LTFT = -12.0 ~ -18.3 Codes: o2 internal resistance high ( I ordered a new 02 and I should have waited to write this haha.. ) System lean because of this issue, but idle is not affected. I don't have any catalysts. I have a 3" downpipe from ebay with no catalysts. I built a custom intake plenum with a 3" ID pipe through a MAF smoothly down to 2.25" after the 90* to the turbo inlet. The car has no oil leaks at all which, I know is shocking for a MK5 with 275K miles - I just redid every seal when i did the head gasket. This car has the most inconsistent boost of anything I have driven. One time it's there, the next time it takes 20 seconds to get that kick in the pants from the turbo. Something feels like it's not closing correctly but the related measuring blocks are all ok. Like boost requested versus boost actual being the same within a VERY small margin.. I think the fuel pressure seems normal at 5 ish bar at idle and going to about 90 - 104 under full load (uphill in third). Totally stumped - I want to fix it then wrap it in plastic until I'm 70.

Thank you and thank you for watching!

Making people laugh is my business... since 2013! =)

The few things I know... I know well.... sort of. LOL! =)

You are too kind! Thank you for watching! Send me your mailing address and I'll send you some of my channel stickers.

Thank you for watching!

Thanks for sharing. Cheers also from Canada.

@@EXOVCDS just seen you are in BC. Awesome! I live on base at CFB Petawawa. My vanagon came from BC 5 yrs ago. Bought it off a man neat ottawa. He looked after making it pretty but was not a mechanic!

Thank you for watching!

Like the commercial says.... Volkswagen, DAS AUTO! LOL

Thank you for watching!

Another lucky / easy find. =)

Thanks for dropping by!

Thank you for watching!

I'm starting to turn into a dirty old man... help! LOL

Thank you... it's a simple, but often overlooked (by novice's) issue. =)

@@EXOVCDS can't scan it for a o2 code therefore it cannot be diagnosed. ;)

Can't monitor o2 on data, so therefore it can't be diagnosed.

How & where are you checking? Post a video so that I can see. It takes 5 to 10 minutes before the sensor will cause a signal change (if it is a single wire sensor)... hold the engine rpm at 2000 rpm and monitor the voltage. Keep in mind that a multimeter shows the "average" voltage. If the o2 sensor is switching quickly, the meter will show the average... which could very well be the .5v that you are seeing. The faster the meter is, the more samples the meter takes and is then able to show more changes in voltage.

I'll put it on my list of things to do.

My lucky streak is strong with older vehicles! =)

Good news is no need to worry about those new parts then... for a while. =)

@@EXOVCDS unless its a dorman part 😂

You as well Terry!

Just a little! LOL

Yes... that's mainly it. A service manual / wiring diagram would have shown the purpose of the shield to him / her.

Just a bit! =)

Thomas EXOVCDS 😊

One of the first & easy things to always check! =)

Your O2's are also shielded... hard to tell from the wiring diagram if it's a similar wire-around-a-wire style or foil wrapping that is grounded.

Wish I could dance like you! =)

@@EXOVCDS Have you tried?? Maybe you can!! :-D

Thank you for watching!

@@EXOVCDS are you open to answering questions that viewers have?

That's what I'm here for.

@@EXOVCDS this is so wonderful 🌈 thank you! My father was housing my 88 2wd vanagon 2.1 for me and unfortunately started blindly adjusting the idle screw to bring the idle down. He was experiencing a higher than normal idle that was bouncing. I followed the Bentley procedure to check the idle control valve for humming checked continuity to the idle control unit and found some pretty corroded connections which I cleaned. One of my millions of questions I have is: If my idle control valve checks good my continuity to the idle control unit checks good and my idle control unit is also good and I'm trying to get the idle screw back to a good starting point should I start the van let it warm up and then disconnect the idle control valve to adjust a base idle speed? If I do do this should I expect the idol to be around 2,000 to 2,500 RPMs if I unplug the idle control valve connector? I have the Bentley manual but seem to be stuck in this circular troubleshooting loop I'm sorry if this question is worded incorrectly or confusing and appreciate your time immensely. Also do you have a patreon?

Turn the idle bypass screw all the way in and then out 1 &1/2 turns. That should put you in the ball park. If idle is still too high at that point, verify that the closed throttle switch is closed (has continuity) when throttle is closed. If yes, tap on the idle stabilizer with a screwdriver when the idle is staying high. If the idle drops when the stabilizer is tapped, clean the stabilizer or replace it. If the idle is still high after tapping, pinch the hose going to the idle stabilizer (from the air intake tube). If the idle drops it could be a stuck stabilizer or bad stabilizer module. Also make sure that the ignition timing is ok.

Honest mistake... but as in most cases, trying to save a buck can cost more in the long run. =)

Does the O2 have a heater circuit? If yes, does it have power?

I believe it does have a heater circuit. It has a single sensor circuit and a double pinned plug which I’m assuming that is the heater circuit

Not sure how to check for power

Disconnect the 2 wire plug and attach a test light across the 2 wire plug. The test light should light up when the engine is running. If yes, then power * ground for the sensor is ok. If no, then you have to check why.

Thomas EXOVCDS , Thanks for the info, I do have power and ground at the plug. I’ve changed the O2 sensor, I had bad ohm resistance across the connector to the heater of the sensor. Going on a trip in a couple days will see how it goes. Thanks again for your help.

Yes, external would be the cheapest & quickest way to go. The stock instrument clusters with Tachometers are getting hard to find.

Yes, true.

Stock injectors have "crimp clamps" on the injector side... I have never come across injectors that had nothing on the injector side of the hose. Post a video so that I can see what you see.

Yes, but I've seen the replacement or rebuilt injectors that are shipped with a short section if hose and no clamp. Looking at this video I thought it looked like the injectors on this van were missing clamps.

You can kind of see the crimp clamps if you know what to look for... I worked on a Van last week where the crimp clamps were so rusty & brittle, that we recommended new hoses & clamps (we don't have tooling / equipment to crimp clamp).

=)

What I have the led light on the cluster never come on when ignition on engine off is there is way to bypass the wiring to the light to see if the led lights is good?

According to the wiring diagram (you should get yourself a service manual if you don't have one), the O2 LED receives ground "through the alternator" when the key is in the ON position (via the same wire that turns the battery light on) and will turn the LED off when the alternator starts to charge. If the battery light is OK, then you have to check the blue/green wire at the back of the instrument cluster connector. With the key ON, attach a jumper wire to a clean metal surface / ground and touch the blue/green wire at the instrument cluster harness plug. If the LED does not light up, then the LED bulb might be bad. If the LED bulb lights up, then the blue/green wire is not connected to or has a bad contact with the alternator field wire (you need to follow the blue/green wire to where it meets up with the blue alternator field wire). The O2 "mileage counter" that I mentioned to you already in one of my replies... is located next to the spare tire. You will also find a blue/green wire at that box... after x-amount of miles, the box grounds that wire to trigger the LED light. If the plug is disconnected, it will not trigger the LED according to elapsed mileage... but the LED should still turn on when the ignition is turned on and go off once the alternator is charging.

Disconnect / leave the green O2 wire disconnected... if the engine runs the same (rough, rich) then it's not an O2 / control issue. Check fuel pressure... probably too high.

@@EXOVCDS how do I test the fuel pressure? The fuel pressure regulator is brand new.

@@justindillon2694 attach a pressure gauge to the test port next to the distributor. Make sure that the coolant temperature sensor (2 wire blue sensor) and wiring are ok.

@@EXOVCDS I did a pressure test and with the key in on position, the pressure is 32 psi and then it starts to drop. When I start the doka it hits maybe 34 but then the engine dies.

34 psi is enough / it should stay running. How quickly does it drop? If one of the injectors is leaking, it can cause a rich running condition. What's the resistance of the blue temperature sensor? If the resistance is ok, it could be a problem with the wiring to the ecm. High resistance in the wiring will make the ecm think that the engine is very cold... the ecm then adds way too much fuel.

85 - 86 is the "control" of the relay (turns relay on / off) 30 is power / battery voltage all the time 87 is the load (ECM or fuel pump relay) I want to make sure that 87 always has battery power (the same power as 30) when the relay is ON. It could be that one of the relays is not supplying full battery power... this can cause problems with the fuel pump or the ECM. When voltage drops below 10v, the ECM can have operational errors.

The service manual outlines some testing / checking. I backprobe the meter to see if any glitches are present during a snap of the throttle.

@@EXOVCDS Thanks :) I love where the manual says 'Specified resistance - Fluctuating'. Not sure if my multi meter is going to much help here. Better start saving for a scope.

How & where are you checking? Post a video so that I can see. It takes 5 to 10 minutes before the sensor will cause a signal change (if it is a single wire sensor)... hold the engine rpm at 2000 rpm and monitor the voltage. Keep in mind that a multimeter shows the "average" voltage. If the o2 sensor is switching quickly, the meter will show the average... which could very well be the .540 that you are seeing. The faster the meter is, the more samples the meter takes and is then able to show more changes in voltage.

@@EXOVCDS same way you checked in the video once the sensor disconnect and once with sensor connected both reading are same

Increase the rpm... the O2 sensor needs to get hot.

Anything older than 8 years... is a good idea.

The sensor after the catalytic converter is a temperature sensor. Was never present on North American vehicles. Europe & Asia only I think (so you have an import import if you are in NA). If ignition items are 5 to 8 years old, replace them (short answer). Service manual lists resistance values for spark plug wires & rotor. Plugs & cap should have 0 resistance. If you need specific info, just post another comment. Perform a compression test first to make sure there's no mechanical issue.

The van is import from Japan and we are in Pei, incase you were curious. 2 of my spark plug wires are very jumpy in their resistance readings, one of which is mostly all the time on open line. I am thinking this is my problem. I will try to figure out how to check the distributor for continuity-could you explain this process? And I want to check the timing of the distributor too-any pointers there? Patrick

@jamessullivan1648 I'll get back to you on Saturday. Weeknights are not good for lengthy replies, sorry.

@jamessullivan1648 Distributor cap needs to be inspected for carbon tracking / wear that could cause spark to travel along the body of the cap to ground, instead of going across the tip of the rotor to the spark plug wire post. The posts inside the cap can build up with corrosion from spark arcing. You can clean off the corrosion with a flat screwdriver. Resistance of each post terminal can be checked with an ohm meter placed across the inside & outside of the post of the cap. Again, if tune-up items are 5 years or older, replace them. Distributor timing does not need adjusting / checking, if the distributor was never loosened / rotated. Even when replacing a timing belt, there's no need to check timing, as long as the cam & crank TDC marks were aligned correctly when the timing belt was installed & tensioned. I timing gun with a degree wheel is not needed, but can be helpful. The engine has to be warm and the ECM gas to be placed into "basic setting" so that timing can be checked. The Bentley service manual has these instructions.

Looks like I need a new distributor. You knew it as it is 30 years old. It is visibly bad with lots of corrosion on points and cracks in rotor. I’ll be getting wires too. When installing is there need for timing work? I can’t for the life of me see the indicator on the fly wheel. Recommend and part brands? I usually use rock auto. Recommend and places to order from?

The relay that has voltage at 87 (with key on) is the ECM relay... the relay that does not have voltage at 87 (with the key on) is the fuel pump relay. This is normal... the fuel pump relay gets activated for 1 or 2 seconds and then turns off. Once the engine is cranking & running, the fuel pump relay will stay active. Yes, monitor both relays (87) with the engine running... that way you can determine if low voltage is the reason for your lack of power.

@@EXOVCDS Having connected the multimeter to pin 87 of the petrol pump relay, I started the engine and it read 13.7volt. After a few minutes at idle, fortunately, the problem has appeared. Shortly after, without doing anything, he is back to normal. 5 minutes later, the problem again but it has not recovered and I have turned off the engine. In another test, the ECM relay, 13.6Volt (pin 87). This time nothing has happened. Normal idle. ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-rSivL_afFeg.html

Did you see my reply about the green wire? Leave it disconnect.

Fuel evaporation rate is the same for a tank that is 1/4, 1/2 or 3/4 full. If no purging were to take place, the fuel tank would collapse due to vacuum build up in the tank, as the level of the fuel drops.

@Thomas EXOVCDS Old car use return type fuel system not return less. Fuel is absorbing heat from the fuel rail before returning to the tank.

Fuel evaporation takes place no matter what... it has to go somewhere, hence... charcoal canister and purge valve. Old cars that don't have purge valve just vent to atmosphere (not good). Maybe I'm not following what you originally meant, sorry.

@Thomas EXOVCDS The reason why gasoline is evaporating is because the electronic fuel pump is inside the fuel tank. It's silly to put something that generates heat inside the storage tank because the boiling point of gasoline is very low. Then it's followed by another silly idea of using the catalytic converter to reduce air pollution by burning more fuel without producing engine horsepower. According to EPA, "By manipulation of total tank pressure, temperature and vapor space a reduction in tank losses can be achieved. When VAPOR SPACE and TEMPERATURE decrease the amount of fuel evaporated decreases. An increase in tank pressure will result in a decrease in evaporative emission. A FULL TANK has very little vapor space and very little evaporative losses" nepis.epa.gov/Exe/ZyPDF.cgi/9100UPF6.PDF?Dockey=9100UPF6.PDF

@@w0lvez1 Good research... thanks for taking the time. I don't have the background / brains / education to be able to keep this conversation going (this is the 6th reply / draft that I have now started). Burning EVAP fumes is more efficient than burning fuel that is injected into the engine in liquid form. Running on fumes is the Holy Grail of engine designs. Keeping the tank at 85%+ is unrealistic... making sure that the EVAP system functions as it should, is time better wasted than stopping to refuel the tank every 100 km's. (-edit- I forgot to add the smiley face) =)