...that's how much I know about working on motors!

If anyone cares to recall from past posts, I had the motor rebuilt several months ago before shipping my 500 Giardiniera here to the U.S.

I've had a bit of trouble recently, and it came on rather suddenly. The motor is running very rough, as if it's misfiring. There's a slapping or slight popping noise and as the motor heats up, it gets worse and loses power. The distributor cap, rotor, points, condenser, plugs and plug wires are all only a few months old. Everything but the plugs look to be in good shape.

However, one of the spark plugs was very dark and looked fouled. So I replaced the plugs and the motor still runs rough. I tried to adjust the timing, but without a timing light, and without a mark on the engine & distributor to line up, it's a chore.

Then I thought maybe the plug wires are bad. So I disconnected the plug wire from the #2 cylinder. The motor started and ran, but a little bit more rough than before. Then I disconnected the #1 plug wire and the motor wouldn't even start?!?!?! I haven't got up the nerve to try the old trick my father showed me to unplug a wire while the motor is running and hold it to the engine block to see if it makes a spark.

So, what in the world would cause the motor to run on one cylinder but not the other??

I remember my mechanic telling me that I would need a valve job in a few thousand kilometers after the motor rebuild. Could a valve on one cylinder be the cause? Would that come on that quickly? I'm a little hesitant to try and adjust the valves on my own. I'm sure it won't be difficult for a skilled mechanic...

Any input would be most appreciated...hopefully, I'm missing something ridiculously simple.

Oh dear!

Problems like this are SO annoying and unfortunately very common with our little cars!

You know, I had a very similar thing happen. It was the morning our car was booked for it's MOT (the annual test we have in the UK to check road worthiness) and it would just NOT run smoothly.

Same as you, everything was new, plugs, points, HT leads, coil, condensor.

Then I pulled one plug lead off, it ran rough.

Pulled the other one off and it wouldn't even start!!

Result: one faulty spark plug, brand new out of the box!!:bang:

Swapped if for another new one and it was fine!!

Good luck and keep us posted!

I'm gonna try and swap the plugs and see if will run on the #2 cyclinder...very frustrating indeed.

If you want to check the spark without getting zapped, borrow a timing light. Nowadays most are inductive and clamp around the HT leads. Instead of using it to time the engine, hook it up and clamp it around one plug lead and then another while pulling the trigger. A pulsing light is indicative of a functioning plug lead and usually means sufficient energy to fire a spark plug.

As these little cars have only two cylinders, they are very sensitive to dirty plugs - if a plug fouls for whatever reason, the engine will run very roughly. New plugs will fix the symptoms but unfortunately not the underlying disease.

You may be able to diagnose the problem by looking at the plug - sooty, oily, burned electrode etc. Most Haynes manuals have a nice comparison chart. Either that or have look on the net.

Let us know how you get on,
Chris

The only parts store in town that carries the spark plug was closed. But, I had a stroke of genius and decided to swap the plugs! That should be suitable for troubleshooting, right? As I was pulling the spark plug from the #2 cyclinder, the bushing came out with it!! (bushing was installed a few months ago when the threads were stipped as the spark plug was ejected while still attached to the plug wire.) So now I'm thinking it's a vacum problem with that cyclinder that has a loose bushing...and I think I still need a valve job...stay tuned!

Sounds like you need a new head.
Are the sedan heads the same as the wagon ones?
Chris

Not so sure about the head. It was just surfaced and re-installed with a new gasket less than six months ago. I could put a compression meter in place of the plug just to be sure, though. Maybe it's just a blown gasket?

I thought that your engine had a valve grind when it was rebuilt or was that photo of the mechanic manually lapping the valves on someone elses' engine?

If the threaded plug inlays are pulling out, the head may not be much good. I guess you can only oversize those plug holes so much before you encroach on the valve seat area. A photo would be interesting.

Chris

yes, that was my motor the mechanic was manually seating the valves. I think those plug inlays - bushings - are not the norm. Isn't the head usually threaded where the plugs screw in? There's not normally bushings, is there? I think they're only installed when the threads are stripped. So maybe I need a new head? THAT won't be hard to find!! LOL!

The heads on these engines are alloy and as with all heads, the plug holes are tapped directly into the metal. The alloy is very soft and overtigtening of the plugs will lead to stripping of the threads with problems later down the track. Plug hole inserts work for a while, but because the inserts are made of a different metal (usually brass, I think) they expand and contract at different rates as the head heats and cools with use. This eventually loosens them.

The other option is oversize plugs, but I don't know whether they are still made any more.

You may find that the sedan and wagon heads are similar enough to swap, though I have no real information on this. They certainly look very similar in the maintenance manuals.

Don't lose hope - it's just a car and this is supposed to be fun, isn't it

Chris