Mono-Motronic - Calling Canadians with Gas!

[vanbcguy]

Yeah, not a diesel, but seems all us Canucks are on here so figured I'd give it a shot...

Just picked up another '94 Jetta, this one has a 1.8L gasser with Bosch Mono-Motronic single point injection.  There's practically no info about this motor since it was never sold in the US - engine code is 'ACC'.  Apparently it's somewhat unique to the Canadian market.

Anyone got one?  Got any tips / tricks / known issues?

It runs perfectly at least at the moment!  Looking back at the AirCare results for the past 8 years though the NOx levels have been creeping up.  If I draw a straight line through the data points I'll be right at the limit next time she goes in for an emissions check.  Figure I should start learning about this thing now before I get there.

[R.O.R-2.0]

my guess is catastrophic converter is dieing..

[DCC]

That engine came standard here in Europe in GT Mk3 Golfs, Polos, Seat Toledos and other VAG vehicles. It also had engine codes GX, JN. 1.8 litre (1781 cc I believe, same as euro-spec Gti engines), 66 kilowatts (90 PS - 89 hp).

If it's just the NOx rising, then probably the catalytic converter is probably not working. Doesn't it sound like if it was full of debris in the inside?

I'd check that and the lambda probe as well. It gives a voltage output (0.2v - 0.8v), and in the perfect stoichiometric mixture, it should give around 0.45 volts.

[Vincent Waldon]

The MK3 Bentley covers that engine pretty well.  It's kinda old skool... for instance, it's the one MK3 engine that still needs a timing light to set the timing.   

[DCC]

The MK3 Bentley covers that engine pretty well.  It's kinda old skool... for instance, it's the one MK3 engine that still needs a timing light to set the timing.   

I did the timing of a friend's mk2 the other day. I hadn't done it for a very long time.
It felt like  

[vanbcguy]

Yeah will check the O2 sensor, probably hasn't ever been replaced.  Mileage is actually pretty low on this car - 116,000 km (or about 70,000 miles).  Good score...

The thermostat is definitely bad, it's almost impossible to get it to warm up even after driving for a good half hour.  Not sure what sensors this system has but it may be altering its mixture based on the temp.  I've got a fair amount of time to deal with it regardless, the AirCare on it is good till January next year and we just registered it now, so no need to have it checked again till November 2011.

It's funny seeing the subtle differences between Mk III's... This is my third one now - two '94s and a '95.  All 3 have different door lock / alarm behavior, this new one only has a single setting on the intermittent wipers (all the others have been "learning" - you just turn the intermittent off/on for the amount of time you want it to cycle and it just repeats that)... No cruise control (not that it ever works in these cars)

Other thing I'm going to have to sort out is the sunroof.  Some dumbass messed it up really good - I think it got stuck open (most likely electrical in my experience) but they went at it with greasy fingers and screwdrivers rather than just popping the panel off and using the manual crank to close it.  Seems the mechanism is half gone (probably still in the roof of the car), lots of greasy fingerprints on the trim around it on an otherwise completely clean car.  Grrrrr...

[Vincent Waldon]

I did the timing of a friend's mk2 the other day.

Now that brings back memories.  Talk about incantations:  disconnect the coolant sensor, blip the throttle three times to clear adaptations, raise idle to 2500, set timing, etc etc.

'Course the dance of the dial indicator is a bit of an incantation as well.   

[R.O.R-2.0]

so, is this system basically just DIGI 2 with throttle body injection?

[vanbcguy]

I think it might even be simpler than that... It's a single-point fuel injector, so one big injector dumping in to a carburetor-style manifold.  No MAF sensor that I can see, definitely nothing in the airbox.  It has an O2 sensor and some other goodies that way but overall it's super simple, there is next to no vacuum hose for instance.  It was replaced pretty quickly by the system used on the ABA 2.0s which was multi-point injection. 

According to the emissions decal under the hood there is "no adjustment necessary" and definitely no exposed screws or anything to tamper with.  I actually don't think the hat has ever been off the throttle body on this thing - it has those VW-style single use hose clamps on the crankcase vent tube so if anyone had taken it off they were a dealership and replaced with factory-style clamps.

Yanked the plug wires, those definitely have never been done before either.  Need some new spark plugs for sure.  This car is so unmolested it's not even funny, especially when compared to Jezebel.

[the caveman]

From what i remember ,they were generally reliable. The 2 issues which seemed to wear/ cause issues was, first the isolation pad under the injection unit, tend to break and cause a gigantic vacuum leak. The other thing was the ground and connections for the O2 sensor. If you look at the r/s engine mount where the connector is, you will see where the shield grounds. Check and clean that ground while tugging at all the other wires there. Seen many where the wires corrode and wear

[8v-of-fury]

A single point injection?? In a 94? Is this not a step backwards?? Even the mechanical CIS was multiport... Why is it like this??

[the caveman]

simplicity i would imagine.
They went through a lot of head gaskets also.

[vanbcguy]

It's a pretty simple system for sure - there's almost nothing to it, I think almost everything is built in to the throttle body.  Interestingly enough from what I've read the MonoMotronic system was actually released in 1990, so long after VW had been running multi-point injection.  I wouldn't be surprised to find it still lives to this day in various foreign markets.  Other thing to remember is up here in Canuckistan we have so few people per square foot that our emissions regs have always fallen behind the US by a bit. 

The car is so basic - for a Mk III it's actually the least equipped I've ever found.  Manual windows, the driver's seat has no height adjustment, no tilt steering, no AC, 1.8L engine, steel wheels, pretty much the only option on the car is the sunroof.  In a way though that's better with VW - "Nothing minor ever works, nothing major ever breaks" - well this car has nothing minor!!  Heck there isn't even a lighted mirror on the driver's side sun visor!

Honestly though it's a great find - super low mileage, it is running like a top despite some of the worst looking ignition wires I've ever seen on a car - pulled one wire off and the connector / top of the plug is just a mass of rust.  New plugs / wires / distributor cap / rotor ordered.  Haven't had to buy any of those in a long while!!

Can't BELIEVE how much more fuel she uses than Jezebel... I've got about 190 km on this tank so far and it's nearly down to a half tank.  Jezebel, despite her relatively high consumption compared to the competition on here, would be down just below a quarter at that mileage.  She's gotten a name now - Gertrude... Jezzie and Gerti!  Still though, tremendously nice to drive.  the 4-speed auto is surprisingly nice.

[8v-of-fury]

I have had a few trips behind a 4spd auto and a 2.0L... They are smooth trannies single point is wayy batter for longevity and ease of fix... But still.. Lol