Solve my problem & win a prize
 

Seriously. My 1994 Pearlie SVX with 38,760 miles is perfect except for the following problem:

1) Above 55mph a cylinder occasionally misfires in a random fashion. This started a few months ago.

What's been done to car since I bought it in December 2006:
New timing belt, belts, crank pulley, water pump, cam seals, spark plugs, air filter, fuel filter, thermostat, PWR radiator, tranny filter, tranny fluid, Mobil 1 oil, brake fluid, anti freeze, brake lines, brakes, battery etc. The car is very clean.

Steps taken to solve problem:

A) Paid Northcoast Subaru $95 to diagnose. They could duplicate but not solve. Said it could be ignition switch, computer, wiring, etc -- no help.

I also used a bottle of fuel injector cleaner.

B) Went to Tom (greatest guy in the world) today.

1) 3 new coils on drivers side
2) Swap 3 coils on passenger side & put sealer on rubber boots
3) Check & clean grounds
4) Clean MAF
5) Road test

Status:

Tom suggested the next thing to do might be replace spark plugs in case one of the new ones was bad. Tom is also going to research this further.

So, I figured why not let everyone participate in the SVX CSI detective saga and offer a prize (or $50) to the person who solves the problem.

Thank you.

Also, I'm sure Tom can add to the description of the symptons and make them a lot easier to understand than I can.

most people on this site seem cool enough that they'd help you without the $50 prize - good luck diagnosing your issues

Is it a random cylinder that misfires, or a specific cylinder that randomly misfires? Or does that still remain unknown?

I know the people here are all cool enough :), I just thought it would be more fun with a prize -- and this does seem to be a harder problem than usual to solve based on a variety of factors.

..It's a random cylinder, randomly misfiring. I'm sure Tom can and will describe it better -- he's working this evening.

There has been a case reported where the plug wires/connections were at fault. This is not so expected, as the leads are not a HT item.

Not hard to check them for continuity, but make sure that you give them a wriggle and shake while doing so.

If this does fix things, give the prize to Chris and the network. :D

I will say knock sensor.

Miss fire due to spark plug lead
 

TREVOR - that was me that had the issue.

During 100,000km service the spark plugs were changed (it was winter here in New Zealand) + some other stuff done like water pump & cam belt etc.

Anyway when cold (the car) there was no issue, but upon warming up there was an intermittent misfire, took it back to my local dealer 3 times before they found the fault - open circuit when warm!!!

So here is the issue - during the re-install of the spark plug leads (either end can do this) the pins are forced backwards slightly - out from the rear of the plastic housing.

FIX = before re-installing the leads use a high temperature silicon RTV type glue just behind the connector body, make sure that leads are pushed forward as RTV is setting.

Worked for my baby!!!!

regards

Steve in New Zealand

I'm going to guess its one of the 3 Right side coils :D

That's usually how my luck would go.

I'll take a stab.

Isolate ALL the plug wires from each other.
Isolate ALL the plug wires from anything conductive {block or groundable surface}.
Now run it.

I see that Plug wires are not in the redo list.
They could be arcing on each other, or on a block area.
This would cause a double intermittent loss, or degredation of juice.

Warm it up, and idle it at night.
Lights off, take a good look under the hood for arcs.
Juice it, and see if it arcs. Heat also makes them more likely to arc.

Had the same problem for about 2 months nobody could find the problem..I change the ignition switch and problem is gone.

Dan... Tom was saying the same thing today but I was determined to believe that if the ignition switch was the culprit, the indicator lights would at least flash. Did ur dash light flicker when it randomly missed?? I will see what I can do about picking up another switch (not the keyed part but the electrical portion. We can give that a go. My money is on that since those plugs are brand new and they weren't mishandled

Tom

Sorry but this does not apply, as the SVX has coils on the plugs. As I pointed out the wires do not carry a high tension voltage. ;)

Tim, not a bad guess. Fault finding by substitution is not absolute. :confused:

The best/cheapest/easiest test, will be to solidly bridge the ignition switch and observe the result.

Curse our OBD-I and its tiny mind! My Legacy used to spit out Misfire-Cylinder 1 on a regular basis, but at least it told me!

The solution was a PP6, but that's not gonna work here, methinks. It might hold an answer, though - lemme look at my books.