Slimwear

While I'm waiting for my recovered dash to arrive I'm trying to complete some of the other maintenance items I've been waiting to do all winter.

In the last couple of weeks I’ve replaced the stock ignition chip with a new one and I’ve replaced the ignition wires with a set of Magna Cores. In the process I’ve developed an occasional misfire at idle. The misfire goes away as soon as the revs climb and it sounds strong in the upper range but it definitely misses when idling. I’ve search the archives but I haven’t found a resolution.

My question is where should I start looking for the problem. It appears to me that my problem could be in any of the following areas.

1)The ignition wires aren’t on correctly. I’ve tried to reseat them a few times but maybe I need to try them again. Could the wire separators have anything to do with it (not on properly, etc.)?
2)The distributor cap was damaged (or something internal) when I wrestled the wires off of the connectors. It did get tossed around a little while pulling the wires off.
3)The coil wire has not been replaced. Could this cause the problem? It would seem to me that if it runs this well that this wouldn’t be the issue.
4)The engine chip is causing the issue. I would think that this wouldn’t be it based on the misfire being occasional and only during idle.

The car ran fine prior to my “fixes” so I’m guessing this is a mechanics error.

Anyone have any thoughts?

Thanks,

Emery
1986 911 Targa

whalebird

Retrace your steps. Make sure all the injectors are pluged in. Try to identify which cylinder is misfiring. A quick and dirty method is to start pulling plug wires at the distriubutor cap when its runnung and see which cylinder the engine doesn't respond to when it's plug is pulled. This is a bit dangerous in that you will have high-voltage arcs at the cap when the wire is pulled. Using an insulated plug-wire puller helps and you can get a shock if you become the ground. if there any fuel leaks you could burn your house down so be careful. I have heard of some of the Magnacore wires being defective when new, but overall they are a superb product and not my first presumption. Check all the basics like the proper wires in the proper location on the dist. cap. I know this sounds a bit elementary, but it is likely something basic. I hope this helps.
Keep us posted and good luck.

whalebird

It may be best to start pulling injector plugs to see which cylinder is dead instead of ignition leads. I don't want to tell you to do something potentially dangerous(I should think before posting). Really make sure that each wire is properly secured on each plug. You'll know the satisfying "click" when they are on and sometimes require deliberate attention getting them positioned on the plug. I have known Magnacore wires to have a strong retaining spring on the plug ends requiring a firm application, but not excesive when done correctly.

ron mcatee

Replace the cap, rotor, & coil wire. If the cap was tossed around, you may have damaged it. If you replaced the wires, you need a new comparable coil wire to go with them. I always change the cap & rotor as a set, not use one with more miles on it than the other.
+1 on what the others comments are. I use dielectric grease (sparingly) to lube the inside of the caps on the plug wires. It allows them to slip over the distributor cap & coil easily and gives a more positive seating in the cap. You can get a small tube at just about any auto store. I suggest doing the simple stuff first, then go to embedded ones such as the chip.

Steve Weiner-Rennsport Systems

JMHO, but I think your problem is related to #2 & #3.

If the cap/rotor is damaged or the ends of the wires, you will get a misfire. Further, if the coil wire is old or not seated correctly in the cap or coil, you'll get the same result.

Make sure the plug connectors are seated properly and that may take some practice if you are inexperienced at this,...

rusnak

This is a great forum.

Slimwear

This is a great forum rusnak!

I'll get my hands dirty in the next day or so and try the suggestions above, I'm hoping it's something simple. It will be 30 degrees colder tomorrow then it was yesterday so I may wait another day but I'll report my findings back to the board.

Emery

theiceman

sounds to me like one of the wires isn't all the way on . the dilelectric grease will allow you to make sure it is on properly.

KILRWAIL

At the distributor end, the boot on the Magnecor wires may prevent the wires from being seated all the way into the contact. Those boots are extremely difficult to slide along the wires to expose more of the end. You might want to try applying a small amount of dielectric or white grease at the back end of the boots, to help slide them away from the distributor by a couple of millimetres. I did and it helped, especially on the coil wire - which I agree you should replace with the one supplied by Magnecor. Good luck!

butzip

I have a Crane Cams ignition in my car that puts out like a 1.1 jigawatt spark and I did this method when I developed a misfire at the Glen. I damn near stopped my heart when the lead arced to the body. I swear I felt it for hours in my arm afterwards.

theiceman

your damn lucky it didnt stop your heart as I am sure no paddles were readily avialable with people who new how to use them within seconds of you ..

Ed Hughes

Three things:

1. You clearly state your cap is damaged-is that a mis-type? If not, replace that as the first logical step, with a new rotor.
2. I'd bet that the boots aren't on the cap as the Magnecors are thick and are tight on the cap. You really have to make sure they are seated.
3. Why didn't you replace your coil wire?

Slimwear

Ed,

All good questions, I’ve tried to answer them below.

1) I don't know that the distributor cap was damaged, I was wondering if it could have been during the wire change and therefore the source of the problem.
2) I've taken them all off and carefully pushed them all back on both at the plug and the cap. Still no improvement.
3) There was a mixup with the coil wire but it has been replaced now (Thank you Steve!).

Right now I still have the same miss. It's only occasional and only at idle, as soon as the RPM's climb the everything sounds great. I think my next plan of attack is to place some dielectric grease on the connections and try again. If that doesn't work is my next step to return back to the stock chip? It doesn't seem to me that it would be the problem but I'm out of ideas. Could I have damaged the cap somehow?

Any thoughts are appreciated,

Emery

whalebird

If no improvement, Ohm each plug wire with a volt/ohm meter from end to end. You should get consistent readings from one wire to the next. If not replace that wire. It helps to isolate the offending cylinder. Start unpluging injectors to see which cylinder is not firing, one - by - one

Slimwear

Any chance old gas could be the culprit here? The car has only been started a couple of times in the last 4 months.

Just a thought,

Emery