1.7 Type 4 Misfire

[dub411]

Hey Guys,

I have a clean '72 411 wagon but it is stuck in the driveway at the moment. Engine has been out of the car more times than I can count on one hand in the past year which is about how long I've owned it. Two transmission rebuilds and a trans-axle later and we were back in business. Right now it won't start. It is missing on one or two cylinders, only the back two(#2 and 4 cylinders I think). The spark is strong, plugs are fine, points are set, grounds are checked, coil is solid, cap and rotor are new, and the misfire is not following the wires(we have rotated them for a quick test as it was originally stuck at a 7-11 until I could get it trailer-ed home). The quirky thing is, when I apply pressure to the right side of the distributor cap, pushing from the high side down, the engine smooths out and purrs like it has 5000 not 250,000 miles on it. And when I let go it sputters back into ugliness. Haven't done a new distributor yet but i really do not have much funds as a high school student. Stumped as is every other person I talk to and looking for help. Thanks, Adam

[Mike Fisher]

It could be dirty trigger points down low in the distributor if it's similar to the Type 3 fuel injection distributor? Trigger points come out of the side of the distributor behind 2 plain end machine screws.
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69 FI/AT square Daily Driver
66 sunroof,67,71,71,71 AT,72,72 AT Parts
56 & 57 oval ragtop $2,500

[Bill K.]

I second Mikes diagnosis - trigger points. Pull the dizzy, remove the trigger points, clean, inspect and replace. Could need new ones as the followers (plastic "legs" riding on distributor shaft) wear out or the points foul. Mine did once. Wouldn't start at all.

http://www.rennlist.com/techarticles/djetronicfuel.htm

I have a "charity" unit. PM me for a deal.

Bill

[dub411]

Now are these trigger points the same as the ones supposed to be set at 16 thousands? are there two sets of points??

[dub411]

http://images1.carpartsdiscount.com/auto/archive/p...points.jpg

These points are set and new[/img]

[Mike Fisher]

I told you last night to look down low on the side of the distributor for the trigger points held in by 2 plain end machine screws. Trigger points are completely different and not adjustable, but cleanable or replaceable. Do you have a 411/412 Manual to help explain/maintain the car?

www.books4cars.com has the Biggest selection of new/used VW Manuals.
_________________
http://s169.photobucket.com/albums/u236/mr_bojangles500/
69 FI/AT square Daily Driver
66 sunroof,67,71,71,71 AT,72,72 AT Parts
56 & 57 oval ragtop $2,500

[Bill K.]

http://www.thesamba.com/vw/classifieds/detail.php?id=938783

they plug in from side of distributor assuming you have original EFI distributor and you don't have carbs

[dub411]

Well I took them out twice and cleaned them but its definately only running on two with the sam problem. New trigger points are on the way and hopefully that will do the trick. Thanks for the help. I'll keep you updated

[raygreenwood]

If playing with the dizzy does this...its not the trigger points its the three prong plug. Its known to be a bad connection issue. Also...its impossible for one trigger set to fail and have the car still run because its a collapsing field circuit. If one channel does not fire...the other does not arm.
This is a ground problem. Check your grund wire bundles on the case centerline. Ray

[E machine]

I have this same problem with my 73 F.I. Porsche 914..all vac lines ,fuel lines,plugs,are good,checked trigger points and took them out and cleaned ,blew them off,put new points and cond in,valve clearence is good,exc compression,fresh fuel,replaced plug wires 4 years ago with cap and rotor,head temp checks out ok,throttle switch works good with no change to the engine when I unplugged it for a diag,fuel pump works and filter changed out.. ...What else could I check?..not sure...the car is only driven about 5 times a year at about 100 miles or so total a year.. guess the shop is the only thing left.... good luck with yours.."E"

[raygreenwood]

The fuel injection ground bundles are suspect...under the fuel distributor. Unplugging the throttle valve switch is not a diagnostic technique...but it does have nothing to do with the tVS at idle.

Things left to check are for vacuum leaks of any type no matter how small, fuel pressure and fuel pressure stability....and wiring plugs at each component.

Cars that are scantly driven are extremely suspect for vacuum leaks at virtually every surface. You also need to check the vacuum holding ability of your MPS...and for Gods sake if you still have a PCV valve...get rid of it and install a fixed orifice.

This is usually a ground issue. What people fail to realize is that if you have on side of the trigger point set failing....the car will not start at all. But if one is high resistance or if one side has shorter duration due to worn cam lobes...it can cause mismatched running.....in diagonally opposed cylinders....they are paired 1 & 3 and 2 & 4.

The wiggle change of idle to the distributor is also a warning sign. It means that you have excessive play and wear in the distributor...and more probably also have rusty and crudded up centrifugal advance mechanism. i would pull the distributor out and strip and clean it and measure the wear and slack and reshim if necessary.

Also check your injector spray pattern. Also check your fuel pressure at idle...it must be stable to 1 psi. If revving it causes notciable fluctuation...you have fuel pressuer stability issues. Ray