Hi, I have a 1994 polo coupe, 1043cc AAU engine, 1.3 AAV throttle body, passat elbow and cone air filter. Recently had new fuel filter and centre exhaust section.

It failed the MOT today on every single emissions item possible. What could cause such awful results, considering the engine runs and drives fine? Please help as the car now doesn't have a valid MOT and I need it back on the road asap. Thanks! Jonathan

Fast Idle Test:

CO: max 0.3% 3.482% FAIL

HC: max 200ppm 234ppm FAIL

Lambda: 0.970-1.030 0.909 FAIL

Second Fast Idle Test:

CO: max 0.3% 3.437% FAIL

HC: max 200ppm 243ppm FAIL

Lambda: 0.970-1.030 0.905 FAIL

Natural Idle Test:

CO: max 0.5% 2.884% FAIL

Does the car still have a cat?

I'd try simple things first, refresh the plugs, maybe change the throttle body and injector back to the 1.0 AAU item.

Yes it still has the original CAT. I may have to try and find a AAU throttle body, but that may be difficult locally. It passed the MOT last year with the AAV TB, mind.

Thanks

give it a good service and put a decent amount of fuel in and take it for a long blast to wake it up. is it running rich?

Probably is running rich, but not sure why. I keep it well serviced with oil and plug changes and often give it a good thrashing on longer drives.

Think I'm going to strip the throttle body down, check the throttle position sensor for wear / damage (very rarely have intermittent starting problems, which I think could be due to this), and check all gaskets for air leaks etc. Then do an oil and filter change incase the rich running has filled the oil with petrol.

I'm hoping a good throttle body and ignition timing setup should help!

Thanks, Jonathan

Incase anyone was wondering how you can adjust the VW monotonic SPI throttle body on AAU and AAV engines, here it is:

http://www.cc.ece.ntua.gr/~achan/Cars/Car_Modifications.htm

are you sure the lambda and blue temp sender are working ok?

Blue temp sender was replaced with a genuine VW item around 8 months ago, made no difference to running.

How could you diagnose a lambda problem? Thanks

usually when the lambda is out its either the cat or the sensor... id replace the sensor and make sure the cats baking hot before you take it in for a retest if it still fails it could be the cat. have you checked the vacum pipes for leaks?

It's certainly running rich, no cat is gonna burn that off. It's over fuelling.

Well here goes.

I stripped the TB and injector plate down, cleaned it all up, refitted to the car and set it up without the filter housing (golf elbow) and air filter off. I did this following the guide posted above adjusting the idle valve screw and the tps. Sounded like it was running great, much more responsive and idled better than before.

I was happy with that, so I refitted the golf elbow and filter, and reconnected the hose which goes from the TB to the intake air temperature sender which is housed in the golf elbow (see picture of part below, stolen from internet). As soon as I reconnected this it ran like shit! One of the pipes on the back was blocked off (would have gone to the flap which controls the warm air from the manifold on cold starts?) and the other goes to the TB. Can someone confirm which hose goes to what pipe on the back of this sensor, I tried both ways but it still ran like crap?

If I unplug this sensor, leaving the connection from the TB open to the air, the car runs great. Does it sound like this sensor is knackered? Or is something else to blame?

Thanks, Jonathan

Edited 24 January, 201412 yr by poloJJ

Anyone?

I'm a carb man but the picture is of a temperature controlled valve, It usually controls engine vacuum to operate the warm air feed flap

preventing inlet tract icing.

Leaving the tube to this open then surely lets atmospheric air be sucked in weakening your over-rich mixture.

Was this with engine cold? Looks like injection cars have a Zusaztluftschieber auxiliary air regulator which I think acts like an electronic choke until coolant reaches 60degC to give stable idle.

Hey chaps, fixed it today but thought I'd update this incase anyone else experiences this and find this thread in a search.

I set up the throttle body as per this guide: http://www.cc.ece.nt...difications.htm

It's a little hard to follow but once you get it right, you'll notice the increase in power! Haha definitely gained some HP and breathed new life in the little 1 litre! I took it for an emissions test and it passed! Took it home and changed the oil and oil filter, which I'm glad I did, the old oil was definitely full of petrol off running rich for so long and was quite thin, so the emissions should drop even further after this! After the oil change the engine was lovely and quiet :)

Thanks to everyone's input, Jonathan

Good news.

But which part of that guide?

Just the TPS or intake air temp compensation or manifold coolant heat re-plumbing mod (fine in Athens I'm sure).

I just followed the guide regarding the adjustment of the idle switch stop screw, and then the TPS, you adjust both with regards to the effect on the throttle valve positioners response.

I didn't adjust the air temp / coolant heat. I hope other people find the guide helpful to throttle body setup on the old spi polos, which are commonly thought to be unadjustable!

Bumping this rather old thread as i may need to adjust my TPI throttle body but the link to the guide is now (understandably) dead. Any ideas?

For the record, I found a rehosted version of the guide at:

http://www.jnc.cz/auto/monomotronic/Car_Modifications.htm

 

The original link in this thread is accessible from the wayback machine, but no pictures would load in that version.

 

My AAU is running a bit rich at the moment, hence the search for links.