Bad idle question and scan attached.

[karlbar2k]

if its a fake cat then the second O2 sensor will have to be mapped out otherwise it will throw a CEL for low efficiency or something similar

[munster]

if its a fake cat then the second O2 sensor will have to be mapped out otherwise it will throw a CEL for low efficiency or something similar

Now I'm getting into the realms of stuff I don't have a clue about!

I'm happy with a standard car, I like reading about the projects regarding remaps, lowering etc but don't really understand a lot of what is said or what they actually bring to the party other than you go faster, so I have no desire to do it to my car!

That said I love being able to do repairs etc myself so just for my own learning why would you decat the car?

[karlbar2k]

Catalytic convertor is put into the system to convert noxious gases into less harmful ones (hence a catalyst) it adds a restriction to the flow so by removing it the engine can expell the air more easily and produce more power and often improve economy.  the MOT test is what stops most people as its a pain to have to keep putting cat section back in just to pass a test, where mine is LPG converted it produces a lot less of the bad gases anyway so if I were to decat mine the MOT would be no problem.

[karlbar2k]

Oh! forgot to add FLAMES

 

if you want a car that spits flames on the overrun then you have to decat

[munster]

Thanks Karl

I'm learning something new everyday . I still haven't managed to monitor the lambda sensors yet but will do so in the next few days (hopefully).

Munster

[munster]

Ok I only did this at idle because I am not really sure what I am doing and borrowed my mates vcds stuff.

The CEL came on this morning so I went and borrowed the vcds.

Block 32 at idle shows 1.9% in the 1st box and -13.3% in the second box. Was I supposed to rev it or go for a drive as well?

 

The normal scan shows fault 16804 catalyst system bank 1; P0420 - 35-00- effeciency below threshold, Which hasn't changed from the last scan.

 

I think the exhaust is blowing at the join between new "cat" section and rear section as it seems louder than I remember on my old Mk 1's but then that was some years ago and I've had a Mk2 in between.

 

I'm keen to rectify this because the wife is reluctant to drive the car at the moment as she doesn't want to break down! I told her it is ok but she is not having any of it!!

[munster]

Karlbar2k tried to pm you but I think your mailbox is full!!!

[karlbar2k]

I will have to go through my stuff but the two readings are additive and multiple-something so basically idle and revving (vac and boost)  give me a minute to find the article  

[karlbar2k]

from memory if the first figure is a positive it is adding fuel at idle which indicates a vac leak (only a small one for you but still a vac leak) and the negative figure higher than -10% indicates it is reducing the fueling at higher revs indicating a boost leak (maybe even the same as the vac leak depending on which pipe is split and if it it before a check valve)

[karlbar2k]

OK I remeber where I got the penny drop moment

 

​http://www.wak-tt.com/vagcom/vagcomamm.htm

 

its the bit in the middle about "Add" and "Mult"

[munster]

Right here's an update, got my brake pipes replaced by the local garage I've been using for years and asked him to see if he could have a look at the exhaust blow whilst he was at it.

He said that the new section of the exhaust had a reducer pipe welded in - badly - and he thinks it should've been TIG welded not Mig welded (or vice versa I can't remember which way round he said) and he reckons it has loads of little holes around the weld area causing the blow. It was all hidden by the exhaust clamp.

So I am assuming that this may be another of my leak problems, oh well these things are sent to try us.

On the plus side my brakes work now

[munster]

New update

I decided to do the exhaust today as I had all the bits I needed to sort it out.

I should've know what with the other issues I find as I go along that it wouldn't be straight forward. Took far, far longer than it should’ve done because of some issues (below) and a trip to the dentist which I forgot about until 5 minutes before!!!

 

Bad - The downpipe studs were FUBAR, one had snapped flush with the manifold, one was mangled and 2 were ok. I tried to remove the mangled one but to no avail, so I soldiered on in the hope that I could get a seal for now! (Standby for a request for help soon to rectify the stud issue)

 

I removed the stainless downpipe and it was labeled as "Toyosport" and when I shone a torch inside I confirmed it was a decat. The bad welding that the mechanic talked about was on the joining piece that comes with the decat, so the decat itself is in really good condition. I will stick it on the for sale board soon as I take pictures of it (Any idea what it's worth please?)

 

When I removed the cross member, which should be holding the centre silencer rubber mountings it wasn't attached to anything, it had also been butchered so it only had retaining bolts for the rubber on one side!! (I don't know why as there didn't seem any reason to do that, again any ideas?)

 

I cut the centre and rear silencers apart on the middle marking and removed the rear silencer. If you are going to do it make sure the car is jacked up high enough so you can turn the rear silencer upside down to aid removal. Took me a while to figure that one out.

 

Putting it back together with a standard downpipe was relatively easy, all new rubber mountings and it sits exactly how it’s supposed to.

 

It is blowing from the downpipe/manifold joint which I’m not surprised about what with the studs issue.

 

So I guess my question is, is it easier to remove the turbo from above, or below, to rectify the stud issue or should I be looking for a new one. Either way I will probably need someone a lot more experienced than I to help/guide/do it with me – any takers?

I do have a spare turbo manifold bit which is in really good condition, is it possible to swap that bit or is that a waste of time?

 

Sorry about all the questions but you lot really are the oracles and my 1^st port of call!