I am experiencing a bit uneven running when only having the primary distributor (feeding lower spark plugs) connected. It is running perfect with only the secondary distributor connected. I have swapped the coils with each other and that made no difference at all. Both distributor caps and rotors have been replaced.

I am suspecting that the problem may actually be caused by that two spark plug cables have been switched by misstake (maybe during last service order by previous owner), therefore I would like like to check that each cable goes to the correct cylinder. I have checked that the cables are correctly connected on the distributors (cables have numbers on them that match the decal in the engine bay). So, what remains is to check the spark plug side.

I am still having my engine tray on, which of course need to be removed (and most likely never installed again...) but how much other stuff do I need to remove just to be able to read the number on the cables (I assume there are numbers printed on the the cables in that end as well)?

I have read some DYI's where it is stated that exchaust system must be removed etc. for access to the lower plugs but I wounder if that is also required just to inspect?

Any support in this matter would be very appreciated

 

You may want to do the water spray test first. Spray a fine mist of water into the engine compartment and look for arcing. It shows better if the compartment is dark and will identify current leakages in the wires.

JNeteler

 

Yes, could consider that. But what I want to check is that the "lower" cables are connected to the correct cylinders.

 

You can run a few tests from the top .
If you are running on only the primary ,
and its not firing every cylinder ,
if you disconnect one spark plug wire from the distributor cap ,
does it run the same or worse ?
If when you pull one wire from the cap and the motor runs just the same
you have found a dead cylinder .
If you find two dead cylinders next to each other ,
maybe the wires are crossed ?

Another thing is the slack in the wire ,
they are cut to length for the run to the spark plug .
If one is slack free and one is having to much slack .

If you have a timing light ,
you might want to hook it to the primary coil wire
and watch to see if the light blinks on and off without fail .
If the blinking light has "good rhythm"
maybe try each spark plug wire to see if each one has "good rhythm" also .
If you find a missing beat anywhere , look upstream .

 

Very good suggestions, thanks. Will check if I can find two "dead" ones next to each other.

But i am still interested to knwo if I can visibly inspect the lower spark plug connectors by only removing the engine tray, or do I also have to remove cat, silencer etc.?

 

You will have to remove a lot of stuff, including the cat and the muffler on the right side, plus the two heat shields, if you want to visualy inspect the wires; as said earlier the wires are cut to length and would be tough to connect to the wrong plug, see attached pics.

Steen

 

Dear Anders

CAT removal is necessary in order to have a clear view along with the vertcal reflective sound deadening panels the under tray fastens to as you will likely want to pull the spark plug wires off in order to see the markings. While you're in there, pull the spark plugs and do a visual check of the spark plugs, they will tell a lot about how each individual cylinder is firing. And if you've gone that far why not do a valve adjust, that can cause an irregular engine fire. Or you can follow the suggestions above (i.e. all of which are excellent) and save some time potentially.

Hope this helps
Bill

 

Its unlikely to be a valve problem because it runs fine on just the secondary .

 

Did some tests according to earlier suggestions. What is strange is that it does not make that big difference no matter which cable I remove, but rather big difference if I remove two at the same time (and here it differs depending on which I remove), but i think this make sense.

After running all those test I am starting to believe that I do not have a major problem, for sure the engine runs better on secondary than on primary distributor but it is not running very poor on the primary, just a bit more rough.

I guess that depending on fule injector location/angle etc. the engine should not run exactly the same on each distributor, or what are your experinces?

 

It should run the same on each distributor, fuel injector location/angle is the same in both cases.
I had a problem much the same as yours, turned out to be a bad spark plug, by the look of it when removed, I don't think it ever had worked.
If you can get your car up on jack stands, it is not that big of a job to remove the exhaust and do a check, well worth the trouble.

 

The location of the spark plug vs injector is different .

 

Very true, but it should still run on all 6 cylinders regardless.

 

From his description above about running about the same with a wire off ,
maybe the 6 are firing , but they are firing poorly because the mixture at the tip of the plug isn't "right" at idle ?

 

The difference is most noticeable when I attempt to quickly rev the engine from idle up to 2500 rpm (still without moving the car), it feels more responsive with the secondary distributor.

 

I am trying to learn something, so bare with me, but wouldn't that be the same for either plug, as by the time the plug fires, the air fuel mixture is compressed 11:1 and evenly present at the tip of either plug, which is identically located in regards to the intake valve, only mirror turned.
My suggestion is still to pull the plugs, because that will tell you which cylinder is the culprit, and then all you have to do is find out weather it is the plug or the wire.