Help, Mot failure, High emmisions

[hopper]

Hi

As the title says, my 86 has just failed its mot on emmisions, the garage seem to think its running rich but there not willing to look in to the problem, they said, because its a import and they cant gets parts off the shelve for it and its too much trouble ,

Anyway, i wondered if there are any common problems that are worth investigating?

There are a couple of things iv'e noticed, 1. on the tvis there is a vacuum pipe at the back(i'll put some pics up in a bit) that has blanked off, but its been blanked by double backing a short piece of pipe then zip/cable tieing it up, the pipe has now perished and it just dragging air straight into the tvis.

2. When i accelarate away, from leaving the car standing for awhile, on first 2 gear changes the exhuast is really raspy,kind of sounds like a rally car, then after the first 2 changes that its sounds normal, not sure if that has anything to do with it, but though i'd mention it.

Thanks for any help.

Hopper.

[alimonos]

my friend there is a plug on the inlet there that can have 3 hoses connected. one for FPR one for map sensor and one for econometer.ALL OF them must be plugged in and in good condition (=must have no air leaks) especially the one that goes to MAP sensor.

[parrot]

I can't see what you are describing on your picture, although the vacuum pipe from the fuel pressure regulator to the plenum looks a bit ordinary, though may be the angle. There is a vaccum take off with three outlets from the plenum as described above. One goes to the fuel pressure reg, one to the MAP sensor, and on JDM cars, the other is usually blanked off. Your third port looks to have a christmas tree hanging off it. I would get rid of that and blank it off properly as it is probably leaking. Any air leak would presumably lead to the ECU trying to richen up the mixture.

UKDM cars have a variable resistor (VAF) located by on the strut tower near the coil/ignitor to adjust idle CO2. If yours is a JDM import it will have an oxygen sensor situated in the exhaust maniold instead. If it has aftermarket headers it is quite possible the oxygen sensor was not reinstalled thus there is no feedback to the ECU.

Lastly, I would thoroughly check for an exhaust leak.

[oldeskewltoy]

New cat tends to help considerably...

My #s were 681 on HC at idle, then 552 at 2nd idle(after 2500 rpm run). I put a new cat in 1st # went down to 400, 2nd # went to 137! 220 is the limit here

Magnaflow and Maremont sell OE sized cats. Magnaflows cost is about $140. Maremont was about $109

[parrot]

Bear in mind that the emissions control for a JDM spec AE86 consists of:

EFI plus oxygen sensor plus three way catalyst (i.e. catalytic convertor) which I don't think UK cars had, and may not have been fitted to yours along the way.

In a nutshell, fix any vacuum and exhaust leaks, ascertain if you have an oxygen sensor fitted, check if you have a catalytic convertor fitted.

Just because they are fitted, doesn't necessarily mean the oxy sensor or cat con are still actually functioning as intended. Also, just because the oxy sensor is in place, doesn't ensure it is connected to the ECU, although it is only one wire from the sensor to the ECU pinout and simple to check with a multimeter.

Not sure what the emissions standard was for an AE86 in the UK back then, but would guess it was EFI and VAF sensor only, so emissions may have been less strict than Jap market.

[hopper]

yeah, she has got a cat, I've posted up a better picture of the blanking pipe.

thanks for all your help so far.

[parrot]

Second photo is better. They look OK as long as they are not leaking.

If in doubt, replace the pipe and do it properly.

What is the story regarding the oxygen sensor?

[hopper]

not sure if the oxygen sensor if functioning correctly, the garrage who did the test were not willing to look into the problem at all, i'll try the test you said using a multi meter,

Just though the car had a bung in the exhuast at the time of the test as well.

[Sanity Clause]

If you've got a stock exhaust system, you might get a raspy noise if the front section is straight through.

I have a modified front section on mine, with the expansion box removed, and a straight piece of pipe in it's place.
It gets a bit raspy, just as you describe.

Never had any problems with MoT emissions. Maybe you should try my MoT man?

[hopper]

the exhaust is stock apart from the backbox,it still has the cat on it, i went to a different garage today, they said it shouldn't fail unless really high, so they put it on the machine in front of me any it was way too high.