412 servicing to cure lumpy tickover?

[shawn71]

Hi all,

does anyone know anywhere I can obtain, and a rough idea of cost, a servicing kit for my 412 fitted with a 1700i engine?

I'm hoping that a good service will cure the slight lumpiness at tickover I am experiencing at the moment. Other than this the car runs well with lots of power, it is purely the lower end of the rev range sitting at a junction.

My thinking is-

if I give the engine a good service changing filters and ignition parts (cap, leads, plugs, points etc) check all other hoses both fuel and air, then check the timing I can rule these out as the problem.

Then if it is still doing it it must be time to work out the fuel side of things.

and I'll be back asking about that


Just as a side question, I fitted a pertronix electronic ignition kit on our bug and was wondering if there is a kit that will fit the 412?

[Editor]

Could be the alternator output is a bit lower on tick-over, which may be causing a bit of a stumble due to a plug not firing well.

Take a look at the plugs some time - it can tell you what's going on in the cylinders. Look out for one that's different - blacker, oilier, etc. It might even be as simple as a gap a bit wide.

For service items try German, Swedish and French (GSF).
gsfcarparts.com list the following:-

SB91030 SPARKPLUG-W7CC T4A All £1.40 each
MMW920/17 OIL FILTER T4A >7/74 £4.25
11611 OIL STRAINER GASKET SET T4A >7/74 £1.50

Sorry, no air filter listed - what do the rest of you use?

Other bits you might need (don't change unless it's clear what's there is faulty - original German parts will often be better quality than these.)
92205 IGNITION ROTOR ARM T4A >7/74 £2.75
92302 IGNITION CONDENSER T4A >7/73 £3.25
92304 IGNITION CONDENSER T4A 8/73 > £3.25
92360 IGNITION CONTACT SET T4A All £1.75
92604 IGNITION LEAD SET T4A All £13.50
92130B DISTRIBUTOR CAP-BQ T4A All £3.80

[shawn71]

Thanks for the part numbers there Editor, might not need them after all though. Although just replaced my voltage tester as broke the last one so shall check the battery and alternator output at the weekend.

Whilst having a nose in the engine bay as one does I was wondering what all the air hoses did?

To cut a long story short I started pulling some of them of and found that some sped up the engine whilst others made it almost die.

I therefore suspect some of the lumpiness is down to a lot of these air hoses/pipes being perished as having pushed them all back on hard it seems a little better.

Anyone know what diameter these air hoses are as I think I shall replace them as one in particular is very hard and brittle at one end and wont form a good seal. I can also hear what I can only describe as the sound of air escaping from a puncture in the engine bay somewhere, is this normal?

Whilst on the subject of hoses, what is the diameter of the fuel lines that connect to the injectors as it looks like all bar one have been replaced, needless to say the one hasn't been done is soaked with fuel which apart from the obvious fire hazard can't be helping the situation.

[Editor]

The fuel lines are 7mm bore, and so are most of the air hoses. The USA guys use 5/16th fuel hose, which is a nice 7.5mm bore so isn't as much of a stretch and lasts better. Good quality cotton covered is hard to find, but the rubber stuff may need a change of clip size and is a tighter fit through the cover plate grommet eg.

Air leaks will mess up the mixture - the intake air distributor pressure is monitored, so if a hose to that leaks air in, you get too rich a mixture (as if the throttle was open more).

The auxiliary air regulator (acts like a choke) lets more air in to richen the mixture for a given accelerator position when cold, but closes off when warm. This is a short hose that goes to the throttle valve.

The big sections of hose on the inlet pipes are 58mm lengths of 35mm bore hose. If you treat them carefully, they reseal OK. Assemble the intake air distributor loosely with them in place, then secure the IAD in place.

[shawn71]

Thanks for the info. Shall have to take a trip to the motor factors in town later on as they are pretty good with lengths of pipe etc.

Might even be able to get hold of some new replacement dipped beam units for me as mine are seriously corroded.