loose Distributor CAP = Perfect idle

[S30Driver]

3 minutes ago, Mark Maras said:

@S30Driver Just curious. Do you know what the difference was in the 1st and 2nd year turbo distributors? If the caps were the same I'm assuming the change was either the dist. shaft diameter or the height or both.

I had a 82 & 2 or 3 83's Mark.  Never owned a 81, the 1st year.  I remember when I bought my ignition parts from AutoSport in Seattle, the early rotor came up and the counter guy there is very sharp, put me on to it so I got the correct parts.  I remember he called his supplier about it but can't remember what the difference was.  I must be getting older ....

Good possibility he has the wrong rotor and or a cheap cap causing his unusual problem.

[S30Driver]

Just now, ira said:

p90A

The P90A is the head that came from the factory with hydraulic lifters.  Therefore the clearance is not adjustable.   However, there is always the possibility that a previous owner converted it to solid lifters.  When you have nothing better to do, pull the valve cover and you can see if you have the adjustable solids.

[ira]

im gonna search the cap and rotor u mentioned, but if u have a link that would be awesome

[S30Driver]

I would call or email MSA, the Z store, and Ryan at ZcarDepot and ask what brand they have and if its a Japanese manufactured part.

[ira]

i would not know if hydraulic or not.  i d have to search unless u have a clea pic.  i can also take a pic and repost it here

[S30Driver]

3 minutes ago, ira said:

i would not know if hydraulic or not.  i d have to search unless u have a clea pic.  i can also take a pic and repost it here

When you remove the valve cover, look at the rocker assembly on any cylinder, if they are solid lifters, you will see two large nuts that lock the clearance adjustment once made.  Also a slot for a screwdriver to make the adjustment on top of the rocker above the nuts.  The hydraulic lifters will not have any clearance adjusters. 

A picture would be great when you have the cover off to clarify, anyone on here will be able to tell you which you have.

[S30Driver]

@Mark Maras   Found the difference in rotors ...

From his pictures, it appears he has the right one if car is later than Jan of 82

                                               Early                                                                                                                  Late

 

[ira]

here are pics..im guessing mechanical ones..

[S30Driver]

Nice!  Looks like it was converted to solid lifters.  One less thing to worry about as the hydraulics have been nla for a long time. 

[Captain Obvious]

8 hours ago, Dave WM said:

pull the plug cap off and replace but not seat on the plug, but rather space it off (estimate about 1/8 inch). With that it would start and run fine, at least long enough to get back to the pit area. Not sure of the science of why this worked, but work it did.

Well beyond the scope of the thread, but...

The theory behind that is that the voltage from the coil will ramp up rapidly until it reaches the point where it ionizes the air in the gap and jumps that gap. By adding that additional second gap, the voltage will rise further before it finally jumps the gap. This is because the effective gap distance is greater and a greater gap takes a higher voltage to jump. By riding the voltage curve higher and holding off the spark a little, you can get a higher energy spark.

It's also helpful when there's a carbon trace buildup. The carbon trace could provide enough of a path to dissipate the coil discharge without having to spark at all. With that second gap and riding further up the voltage wave before discharge, you can sometimes burn out the carbon traces.

 Assuming, of course, that your coil has the nuts to consistently jump a gap that big. There are plenty of risks, but (as you found) in the old days, it could sometimes get you home in a pinch.

[ira]

 

@Captain Obvious, tnx for chipping in.  I'm sure Dave is happy to read that.

 

@s30 Driver....attached is how the Spark plugs look like.  these are 2 week old plugs. 

Plug #6 received a new injector.  

I noticed the valve cover screws were not tight, which explains some of the oil spill.  But what is the reason for the tip on Spark6 to be diff than the rest? Why is fuel not burning there? or is there no fuel getting there?

Let me know guys if this should be in a diff subject.  

tnx again.

[Dave WM]

hmm well 6 look suspect for sure, the rest seem rich. this is where the color tune would come in handy, you can see if its sparking and evaluate the burn.

I would move that #6 injector to another cylinder, get a new set of plugs, and see if the problem follows that injector.

Also I noted your are running a plug I don't recognize. generally speaking NGK standard plugs are run with great success on L motors.

If moving the injector has no effect then clearly there is a spark issue going on.

did you try lifting the plug cap off a bit so there is a spark gap between the plug and the boot? just get it off a tiny bit and see if there is any change in idle.

oh and do a compression test to rule out that as a problem, check all cylinders and look for even pressure.

Right now I am kinda ignoring the "runs better with cap lifted". I don't doubt you its just something that does not have a clear connection yet.

looking for compression, fuel, ignition even on all for now.

 

Edited November 3, 2020 by Dave WM