Test Ignition Coil

[Kaliv]

Is there an easy way to test if my ignition coil is working properly without throwing a new part in there and seeing if that clears up my problem? Thanks!

[James Brown]

sure for a 87 model?

[James Brown]

this is HOW you test it, but might not be for your coil, post the test results and we will go from there.

[Kaliv]

Alright, I tried checking the primary but my ohm meter only reads in the 100s, so I couldn't check it. On the secondary though, I was getting readings of 5.85K...although occcasionally I could get it to flicker up to 7K. My guess is that my coil really is the bad part? Would this be causing a hunting issue?

[timmy2]

What year?

[Kaliv]

1987 non-turbo. Also...a guy at work told me I should look into my ignition module (and that it should be sitting near my distributor cap). I don't see anything through. He said I should trace one of the wires (can't remember if he said green or black), but it almost looks like they both go into the back of the car. Does an '87 have an ignition module...or does the DME do that work?

[dshepp806]

I'd get a better meter to measure the intitial checks correctly. With everything disconnected, BTW.

Then go from there.

Best!

Doyle

[Kaliv]

Stopped into a Pep-boys tonight to see what kind of multimeters they had. They looked like they had the same range meters I have, so I didn't buy anything. The worker there said more than likely it wasn't my ignition coil, but I'd probably need a new distributor or plugs. Eh, he didn't have them in stock anyway when I told him what kind of car it was...so it was no pressure for me to say no thanks.

Originally Posted by dshepp806

With everything disconnected, BTW.

Came home and thought I'd try this disconnect thing. Makes me feel more confident anyway.

Setting multimeter on 200 ohms: the primary is bouncing between 0.8 and 0.9.

Setting multimeter on 20k ohms: the secondary reads 5.74. If I'm reading this right...I'd say that's 5740 ohms. Is that right?

According to this thread: Bad Coil?
The primary should be between .4 and .6 ohms and the secondary between 650 and 790 ohms?

Does anyone concur with this and does it make sense that when coils go bad they have more resistance? My car will start and stay running for a while...although it hunts between 800 and 100 rpms at idle. Occasionally it will stall out.

[Kaliv]

While I was taking the coil out...I uncovered a few wires that aren't attached to anything.

First...the black arrow...is a bunch of brown wires. I figure they are probably just ground so I stuck them on one of the bolts to hold the ignition coil in place. Is that what they are...ground? No problems putting them there right? Better than just hanging loose in the engine compartment?

Second...the green arrow...is pointing to two wires that also don't seem to go to anything (just hiding out behind the ignition coil). One is red with a black stripe and the other is brown with a white stripe. Anyone know what they are for...are they important? Better yet...where do I plug them in?

[h.wong]

coil specs according to the Bentley Manual for Carrera 84-89

is primary .4 -.7 ohms

secondary 5000 - 8700 ohms

Hope this helps.. good luck!

[Tippy]

The coil shouldn't have anything to do with surging idle. Vacuum checks, base idle settings, and AFR's need to be checked.

[T77911S]

dont get hung up on a few tenths of ohms. its electronics.

with the meter. setting it to 200 means that is the HIGHEST reading you can do on that scale.
it will still read down to 0 ohms.

agree with tippy. does not cause surging.

dont know about the other wires but the browns ARE very important.
if that is were the coild was attatched, they came off when the coil was removed.

not a good idea to take advise from pep boys on a 911. for that matter, not anyone that is not familure with these cars.

[Kaliv]

Ok, I think my problem is solved. At least it wasn't hunting for the small test drive I gave it tonight.

Plugged the ignition coil back in. Decided to leave the group of brown wires on that post instead of letting them hang loose in the engine compartment like I found them. I tried finding a home for the wires with the green arrow...but just let them where they lie because I couldn't find a home. But while looking around I found out that my O2 sensor wire was unplugged. You can see one end of it right below the yellow sticker on the grey wire with three dots...about 4 o'clock from the green arrow.

So I'm going to guess my original hunting problem was probably the O2 sensor coming loose. Oh well...I learned something about coils.

[LakeCleElum]

Originally Posted by Kaliv

Setting multimeter on 200 ohms: the primary is bouncing between 0.8 and 0.9.

Setting multimeter on 20k ohms: the secondary reads 5.74. If I'm reading this right...I'd say that's 5740 ohms. Is that right?

According to this thread: Bad Coil?
The primary should be between .4 and .6 ohms and the secondary between 650 and 790 ohms?

To test the primary side, set meter at 200 ohms and then connect the two leads. Subtract this reading from your final reading.....expample: reading of .05, subtract from the .8 to read a .75