My S2 coupe bit of a rebuild and repair thread.

[Jaswan]

Good luck for today!!

You will be fine

Jase

[newsh]

Our fingers are crossed for you :-)

[B5NUT]

Well it passed with no advisories. However, the emissions where on the high side and the exhaust gasses do smell a little rich. So I've ordered a new Lambda sensor. I've recently had the injectors cleaned so is there anything else that would make the car run rich?

[Tractor Dave]

Dead or dying cats

[B5NUT]

The exhaust was custom made for the car some time around 2008 and the car has only done 2-3K miles since then. It could be these are just empty shells and it's yet another job the last owner did on the cheep.

These are the two cats off the car.
cats.jpg

[Jaswan]

MAF sensor?

[B5NUT]

Have been told they just fail on the S2, and it makes the car somewhat undrivable, and the car drives very well. Have also been told the temp sender on the back of the head could be giving false readings.

[Bowie69]

Re:Central locking, warm weather helps dry things out, and things start magically working again

Also, your tinkering, may have lodged things in the right place by accident

Fingers crossed it is long term

[Lago Blue]

Re: Running rich

While waiting for a new lambda sensor, know that they can be tested in situ. for function (w/ a good automotive DMM), and that the following may be much cheaper and help prolong downstream component life.

If those exhaust readings/smell check are taken at idle, it may be that the FPR is either not receiving, or capable of holding full warm engine vacuum, which should be 18 to 19 inches of water column at idle. As you may know, full vac. is required to both reduce fuel pressure at idle, and to also have that fuel pressure ramp up when not, as the ECU is expecting to have use of that full range of fuel delivery pressures (from fully reduced, to full) during those rapid transitions both to and from idle. What this does is balance fuel pressure to the instantaneous (and quickly varying) manifold vacuum, to achieve close to correct fuel delivery, such that the O2 sensor et al; can then possibly manage the last little adjustment.

From the Audi 20v Turbo training manual:

"The pressure regulator maintains
the fuel pressure at approximately 3 bar (43.5 psi)
above intake manifold pressure."

"At idle, only a small quantity of fuel is needed to
maintain engine operation. Vacuum from the intake
manifold is applied to the diaphragm and spring in
the pressure regulator which allows more fuel to
return to the fuel tank to maintain correct fuel
pressure."

Even though there is a dedicated vac. line directly from the I/M to the FPR, the I/M itself may not ever contain full engine vacuum for use if there are leaks out in any of the various branches of the vac. system. Typically, it's the hard plastic and soft rubber vacuum plumbing that becomes defective first, but the FPR diaphram can leak also (can create a kind of 6th injector effect!). One can do vac leak-down tests over time for the entire vac. system, branch by branch (all the way back to the rear. diff actuator on a Cq) to check for leak locations.

If less than current century thick-walled proper synthetic small-bore vac. hose is used (the now less than current BMW dealer issue smooth exterior black hose is very good and has correct ID for tight connections on our existing Audi vac plumbing), under-spec hose can partially (with heat and/or hose bends) or fully collapse in use, impeding vac. delivery.



BMW vac hose Screen Shot 2022-05-28 at 10.13.50.png image_85212.png

[B5NUT]

Thanks for the information. The engine is my next study program as it were. I just need to find a good service manual on the ABY engine.

Just after I put the post about the rich running of the engine I did a search and a forum member PM'd me with a few fault finding idea's. One of them is the coolant temperature sensor. With the initial over heating problems I was having with the car about 6/7 months ago I purchased every temperature sensor on the car, but I never got around to replacing that sensor. So this afternoon I have replaced the coolant sensor on the back of the block.

I've also ordered a new Lambda sensor and that should be with me on Monday morning so it will be replaced then regardless. I've Just seen how to test a lambda sensor, and wondered if it can be done with the sensor on the car. So I just set the meter to read DC voltage, connect the positive lead to the black wire on the sensor and the negative lead to the harness on the car and then start the engine. From what I understand a good Lambda will generate about 1 volt. Or is it best to remove the sensor off the car and do the blowtorch test?

Had a look for the part number on that BMW hose and after a quick google search it's only coming up with search results from the US. Need to see if I can find something from the UK.

Currently my DIS is reporting MPG of around 26-28MPG. However I think it's dropped a little over the last week or so to around 24MPG. Not a massive drop but a drop. Out of curiosity is my mpg good bad or just plain ugly? Note it's standard ABY S2 not mapped in any way.

Also this is the first time I've put the car through the MOT. So I have no idea what the previous reading were. Also the last MOT was not worth the paper it was printed on there were so my issues on the car it should have never passed an MOT. The last tester must have got a hell of a back hander to pass that car with no advisories!

The vacuum lines on the car don't look the best and some to appear to be a little lose it be the fact the ear clamps have badly rusted and not gripping the pipe very well. So I will have to replace them regardless. Just need the pipe and some correct size ear clamps.

[johne]

The new lambda sensor needs to be genuine Bosch, lambdas are one of the worst areas for cheap copies that don't work well, should cost you around £60.

You can read your lambda values in VagCom if you have that or you can buy a cheap narrowband gauge for £15 to read the values. Using a DVM to do it really isn't that easy - should be around 0.5 volt BTW.

Your MPG figures sound reasonable for around town driving, you need motorway cruise to see the 30's.

Our cars are hard to get the cats up to temperature for the MOT emission test especially if you have no insulation around the pipes between the turbo and the cats.

Your "high emissions" may be no more than the combination of poor aftermarket cats and them not being hot enough to work properly for the test. How many times did the tester have to run the test to get the machine to pass you?

and do make sure all your small vacuum pipes are in good order......

[B5NUT]

Thanks John, The sensor I was able to next next day was an NGK one and it's from an Alliance Automotive group factors so it should be a good one. I would have rather have a Bosch sensor but that was all that's available in the short term, and NGK are a good brand and they are the only ones that do the plugs for the cars these days. However I will source a Bosch sensor as a backup.

There is insulation on the downpipe but that's about it. It could be the cats were not fully up to temperature. Tomorrow when I replace the sensor I'm going back to the garage as he said would keep checking the emissions until it's fixed. He known's what I'm like with my cars they have to be right.

Just had a quick look at the history of the car and there has been nothing there about emissions, But I guess a pass is a pass regardless of how close it is to the limit line.
mot history.jpg

[newsh]

If the vac line to the Fuel Pressure Reg is leaking a little it can cause rich running off boost and lean running on boost. A bigger IM leak can cause the reverse! Everything from the MAF onwards needs to be super airtight.

Your mileage is pretty good but might get better yet

Clean or replace the pins in your MAF connector if you haven’t done so yet.

[B5NUT]

Well the NGK Lambda did not arrive at the parts supplier. So have 2 Bosch sensors on order from different suppliers that should arrive tomorrow.

In respect to the pins on the MAF connector they all look in very good condition, they look like they are gold plated...
connectors.jpg

[K Simmonds]

Yeah they do look good, nice and clean as well as tight. I can't recall if their Gold plated as stock (I think they are) but we did a at least one group buy of replacement Gold plated terminals on here a good many years ago as I can remember doing mine. Was the previous owner on here?

Bosch senders are a better job so perhaps that's worked out for the best, though I'm not going to start slating NGK's stuff, as rule they're pretty good quality.