So you bought a new 3wire O2 sensor? If so, the black is the signal not the 
ground. (The sensor is grounded through the exhaust?) 
After the orange connector the signal wire back to the ecu is a little thicker 
because it's a coaxial cable, it has a braided shield around the signal wire. 
This shield has a ground and I believe that's the one going to the firewall. 
That's why they look like 2 wires fused into 1. 
(I think, my loom is different.) If I'm way off, I hope someone will let him 
and me know. 

There should be an extra female connector for the 2nd knock sensor, unless they 
cut it off. 


On Mar 23, 2016, at 6:30 PM, damac2004 <damac2...@sbcglobal.net> wrote:

hate to bug people but i'm just tidying things up with a new 02 sensor and want 
to make sure before i start it up and time it.  i pulled the whole harness that 
goes to the ecu just to make sure.  i do only have the 1 knock sensor.  don't 
see any special shielded wiring.

the 02 harness side  has a black ground going to firewall that goes to the ecu. 
 a small area is cleanly exposing wires and the 02 sensor signal wire connector 
is fused to this ground leg.  no sign of solder or cuts, looks original to me?

i also tried looking up my car in the bently and it matches a later gti 91 
chasis according to them.  it shows the ground location over there on firewall 
rather than the engine block.

i have the 2 white wires from 02 sensor going to stock connectors and their 
colored wires into the ecu harness. 

bently shows the ground leg black wire and the 02 sensor connector black wire 
making a left turn into that black ground wire.

so it seems it is wired correctly?   

i just don't understand how 02 sensors work, not sure if that black wire is a 
ground wire on all car applications.

> On Saturday, March 19, 2016 at 1:24:08 PM UTC-7, stevenarguello wrote:
>  The wire you’re touching looks like the O2 signal. In your case it looks 
> like the shield might have been pulled off and ran to ground. (That’s a 
> guess, could be like that from the factory) The red and yellowish (sorry, I’m 
> a little color blind) are the O2 heater. The 2 whites and the lead with the 
> electrical tape go to the sensor. 
> I think.
> 
> There’s only one mounting point for a knock sensor on the 1.8, the 2.0 has 2. 
> If you have 2 and they’re both mounted to the block then I’d say that the 
> block is 2.0. I know we’ve gone back and forth on this, but I had the exact 
> opposite happen to me my ’88 had a 2.0 (the PO didn’t know) I found out when 
> I discovered the second KS.
> 
> On Mar 19, 2016, at 3:20 PM, Holland Phillips <holland...@gmail.com> wrote:
> 
> As Steve mentioned, the O2 sensor signal wire is shielded, similar to a 
> coaxial cable. It's basically a regular insulated braided copper wire of 
> about 20 gauge, with a braided shield covering it.
> 
> ~Holland
> 
> On Mar 19, 2016 12:13, "damac2004" <dama...@sbcglobal.net> wrote:
> im pretty sure i have 2 knock sensors?  im attaching a picture of what i 
> uncovered from electrical tape.  looks like a brown wire covered with black 
> that goes to top connector from drivers side, its duct taped along i guess 
> stock loom.  i assumed ground at first but wonder if this could be the 02 
> sensor signal wire?
> 
> and just what i thought.  i have a black ground wire coming from firewall 
> gong to the loom.  but an area is all cut away with exposed wiring.  the wire 
> from outside of loom was wrapped into this exposed ground bundle WITH the 02 
> sensor signal wire???
> 
> this is incorrect right?  ground wire is no the same as signal wire for 02 
> sensor it should make an isolated run somewhere?
> 
> whats wierd is all the wires but the loose one outside of loom seem to be 
> fused together.  i can't detect solder and the wires seem to be attached 
> firmly inside the black cover.  i can't even pull them apart, i would have to 
> cut which makes me think it was stock because i don't see breaks further down 
> the line.
> 
> 
> 
> 
> 
> On Saturday, March 19, 2016 at 10:29:29 AM UTC-7, stevenarguello wrote:
> On a typical 1.8 CIS-E the O2 signal wire is shielded and green to an 
> insulated male spade connector and there are 2 white heater wires into a 
> duplex VW connector. I’m not sure how big of a deal the knock sensor issue 
> that you’re going to have is. Your Motronic ECU is going to want 2 knock 
> sensor signals, I think it uses one as a baseline reference and the other 
> adjusts the spark timing. The 1.8 block only accepts one knock sensor.
> 
> On Mar 19, 2016, at 11:31 AM, 'Matthew Yip' via MK2-16v 
> <mk2...@googlegroups.com> wrote:
> 
> This reminds me of a friend who adamantly stuck to the theory that VW and 
> Audi engines are the same because of the engine code. Instead of moving the 
> accessories, he installed the complete 1.8t from a VW into an Audi TT. 
> 
> At start-up, it fired immediately but idled at 2000 rpms. Why?  Because VW 
> had a 1" fitting underneath the manifold that Audi doesn't use. The moral is 
> to never assume and always check the obvious since the obvious isn't always 
> obvious <G>
> 
> - Matthew -
> 
> On Mar 19, 2016, at 11:03, Holland Phillips <holland...@gmail.com> wrote:
> 
> Progress! That's awesome! I don't remember the wire colors anymore, but yes, 
> one of the wires to the O2 sensor is the heater wire. Hopefully, once you set 
> the timing, it will improve things. However, until you get the O2 sensor 
> hooked up correctly, it isn't going to run right. But at least you've 
> resolved a lot of your issues. I'm happy for you.
> 
> ~Holland
> 
> On Mar 19, 2016 01:38, "damac2004" <dama...@sbcglobal.net> wrote:
> well i capped off one hole with a bolt/washer and the other with a thick 
> plate and gasket.  turned the key once to hear the pump prime and then tried 
> to start the car and it started right up and idled a bit less than 900 rpm i 
> think.
> 
> wow do i feel stupid.  
> 
> i got various little things to fix after poking around but my next problem is 
> the cat/02 sensor.  i'm going to start fresh with my new cat and 02 sensor at 
> this point.  i assumed the wiring was ok but noticed some previous owner 
> electrical tape and there are numerous wires tied together into a bundle 
> thats hooking up to a ground on the passenger firewall.  this includes a 
> single wire that is zip tied to the outside of the loom coming from the 
> drivers side.  halfway it turns from black to brown with vw plastic 
> connectors.
> 
> seems a little goofy at face value to have a single wire shoot all the way 
> over there for ground right where all those wires meet. i have to look closer 
> but i think something is screwed up if im reading right the 2nd 02 sensor 
> connector is a heater wire NOT ground?  the other harness with 2 white wires 
> goes into the loom.
> 
> i have a feeling car isn't even getting a signal from 02 sensor so i need to 
> get that straight before installing new one.
> 
> i had the distributor at the old setups marks, i will have to time it 
> tomorrow i couldn't actually see the marks well when trying the timing light 
> in the dark tonight.  car runs and is revving out with the stock chip/cams, 
> etc. but i noticed right away when i stab the throttle and it comes off the 
> idle switch there was a slight gurgle and then it revs out but is reacting to 
> pedal.   i'm hoping it needs to be timed and that will help.  
> 
> On Wednesday, March 16, 2016 at 7:56:36 PM UTC-7, damac2004 wrote:
> oh boy i am feeling stupid and think i have found the smoking gun here.
> 
> is it possible that having 2 open holes on the back of the intake manifold 
> made the car act this way?
> 
> this is not a california chasis so no egr stuff.  when i pulled the euro 
> manifold one hole had a bolt stuck through it with rtv and another hole was 
> held by bolts and gasket.
> 
> when i was transferring everything over to the stock manifold i remember 
> poking down the hole with brake cleaner hose and hit what i thought was solid 
> wall on each.  at the time never seeing egr stuff assumed it maybe would be 
> drilled out for a car that needed that hardware.
> 
> i had filled the holes up with brake cleaner with that side up and don't 
> think i paid close enough attention so this whole time it was installed on 
> the car like that.
> 
> tonight as i went to transfer the old parts back on as my last hope effort i 
> noticed some leakage when spraying brake cleaner and a light bulb went off.  
> so with those holes up if i spray one hole it fills the other hole up.  if 
> you leave the manifold sit the level of fluid just sits there.  when i went 
> to tilt sideways one way nothing happened but leaking out the top.  when i 
> tilted the other way 2 of the runners leaked the fluid out.
> 
> i don't know these cars at all.  since the car wasn't running right i never 
> wanted to let it run long since it wasn't acting like a real car.  my mom was 
> watching and said i see some smoke and it sounds funny but of course i told 
> her its just stuff burning off and that it wasn't running right.  couldn't 
> really take a chance to look or feel closer.
> 
> i have seen people mention these cars can run crappy with vac leaks and they 
> don't run without the intake tubes attached?  i'm hoping this is what it was. 
>  going to make some block off plates and gasket to seal those 2 holes up 
> tight and then install all the old parts on it and hope like magic its back 
> to normal and then i can smog it.
> 
> On Tuesday, March 1, 2016 at 10:41:38 AM UTC-8, hollandphillips wrote:
> I just thought of something. Any chance the fuel in the tank could be 
> contaminated? Since I think you said you're in California, the fuel here is 
> probably the worst in the U.S.. With the ethanol and other crazy additives 
> that's in it, it has an extremely short shelf life. 
> An other thing, I wonder how the fuel pumps are? If either the main or 
> transfer pump aren't healthy, that can cause weird running problems. The 
> easiest way to check the pumps is to disconnect the input line at the fuel 
> distributor and have someone turn on the ignition for a second. You should 
> get a really healthy stream of fuel. As I recall, the main pump operates at 
> around 50psi, give or take. 
> We're reaching for straws at this point, so the more you check that looks 
> correct, that's fewer possibilities to deal with.
> 
> ~Holland
> 
> On Mar 1, 2016 10:15, "Larry Velez" <la...@sinu.com> wrote:
> I just checked and Marren is still in business and still rebuilding injectors 
> of all ages:
> 
>  
> 
> https://www.injector.com/
> 
>  
> 
> https://www.facebook.com/MarrenFuelInjection/
> 
>  
> 
> -Larry
> 
>  
> 
> From: mk2...@googlegroups.com [mailto:mk2...@googlegroups.com] On Behalf Of 
> Holland Phillips
> Sent: Tuesday, March 1, 2016 12:56 PM
> To: mk2...@googlegroups.com
> Subject: Re: [mk2-16v] how do i find out what engine i have?
> 
>  
> 
> I agree with you Chad. At this point, I would perform a compression test. If 
> that looks good, then I'm at a loss as to where to go next. Maybe look at the 
> injectors. It's probably easier and cheaper to try and find some used, 
> hopefully known good injectors, even if it's only one. Then you could swap 
> them one at a time and see if you find a bad one. There are a couple of 
> companies that do balancing and blueprinting of Motronic injectors. I had 
> mine done by Marren Motorsports back in the mid '90's, so I don't know if 
> they're still in business. They could perform just testing to check for flow 
> and pattern.
> Beyond that, I just don't know.
> 
> ~Holland
> 
> On Feb 29, 2016 18:21, "Chad Rebuck" <chadr...@gmail.com> wrote:
> 
> The key in the cam gear is only there for the alignment until the bolt is 
> tightened. It doesn't really hold the cam gear in place once the bolt is 
> tightened.  Same for the crank pulley too.  The key can break if the bolt 
> gets loose enough for it to turn. 
> 
> I'm just curious how the engine sounds as you said it ran smoother for a 
> short while when you opened up the throttle.
> 
> I'm about out of ideas.  If you take it to a shop the first thing they're 
> going to do is check the timing again and check the compression I bet.
> 
> On Feb 29, 2016 9:05 PM, "damac2004" <dama...@sbcglobal.net> wrote:
> 
> im afraid to run this car for long but what would be better, a video from the 
> engine bay or tailpipe?
> 
>  
> 
> i didn't change the plug order, etc. when doing all this work, just popped 
> the distributor off and layed it in engine bay with battery out.
> 
>  
> 
> the cam i took off the car did have the cam gear tooth broken but it didn't 
> move based on how the keyway lined up, is that surprising?  i bought another 
> cam pulley off a vortex member and he sold it to me the exact same way and 
> told me every one he has taken off came the same way?  i thought that was 
> nuts but have seen through forums searching it has happened to others.  i got 
> a new cam pulley while doing all this work and its still fine.  and i have to 
> assume the crank is fine as well since it was good running and all the marks 
> are lining up correctly still.
> 
> On Monday, February 29, 2016 at 5:56:38 PM UTC-8, chadrebuck wrote:
> 
> Also check that the cam sprocket is located in the right place on the cam. If 
> the tooth broke off of the cam gear then it could rotate causing the timing 
> to be incorrect. Did you mention that the cam sprocket had a broken locating 
> tooth?
> 
> On Feb 29, 2016 7:47 PM, "Chad Rebuck" <chadr...@gmail.com> wrote:
> 
> Changing the cams out will be a waste of time. What did you do to verify the 
> spark plug wire order? Can you take a video of how the car is running?
> 
> On Feb 29, 2016 7:39 PM, "damac2004" <dama...@sbcglobal.net> wrote:
> 
> i put the techtronics chip back in and put the older throttle body back in 
> with no changes in how the car is acting.  i also checked grounds and ran 
> some extras to the bundle on head, etc. just in case.
> 
>  
> 
> my issues make for a useless car, no way it could be driven.  so my problems 
> seem way beyond the little tuning people do to get their cars running right.  
> this car ran and drove when i got it with very old and worn injector seals 
> and numerous vacuum lines with holes in it. it ran its best when hot and on 
> the throttle never gave out on me or died. although it had goofy issues with 
> starting consistently and idling a little high/rough/inconsistent at times.
> 
>  
> 
> and i see people mention 02 sensors and cts making for a rough running car 
> possibly but again this is way worse than that.
> 
>  
> 
> i'm stuck so tomorrow i am going to put the old cams, etc. back on and cross 
> my fingers.
> 
> On Saturday, February 27, 2016 at 8:41:59 PM UTC-8, hollandphillips wrote:
> 
> Since the Mk 2 cars were all pre OBD, they had only one O2 sensor which was 
> mounted before the cat. So the ECU never knew if the cat even existed or was 
> functioning properly. Now that I think about it, if the O2 sensor has no 
> output, or was not connected, the ECU will go into "safe mode", which is full 
> rich. Hence your poor fuel mileage. I also recalled that the O2 sensor on the 
> Motronic cars is a three wire type, which means it has a heater, so its 
> output will become valid more quickly in order to reduce emissions. All this 
> is bringing back memories of all the 16V trivia I acquired over the years. 😐
> 
> ~Holland
> 
> On Feb 27, 2016 20:00, "damac2004" <dama...@sbcglobal.net> wrote:
> 
> i could test compression but it it did drive fine before i tore it all apart, 
> after this incident.
> 
> this car had no cat so 02 sensor was laying underneath airbox this whole time 
> :).
> 
> i thought the car stunk and i got bad mileage but this car was fun to drive. 
> i was beating on itand it pulled when i stomped on it all the time
> 
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