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Coil Pack Resistance Testing


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15 replies to this topic

#1 intrigueing

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Posted 04 March 2004 - 09:15 AM

95 leg auto. My wife had the car die at idle at a stoplight, she said it took a while to start, and since then (a week) I have been driving it with no other problems. I started poking around looking for problems, and tested the coil following my chiltons manual. Here's what I got:

Spark plug post 1-2........ 2 Ohms
Spark Plug post 3-4........ 2 Ohms
Harness Post 1-2........19 Kilo Ohms
Harness Post 2-3........19 Kilo Ohms

These #'s are WAY off what the chiltons says. What should they be? Is the thing toast? Or is my cheap-o multi meter junk?

I'm thinking the IAC may be the culprit, as it died at idle - perhaps time for a cleaning - anything else I should check?

#2 Legacy777

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Posted 08 March 2004 - 09:19 AM

The coil packs on the 95's are the same as the diamond's found on the early gen legacy MT's.

You'll find the specs and testing procedure here

http://www.main.expe...oilpacktest.jpg

#3 intrigueing

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Posted 08 March 2004 - 10:46 AM

Thanks Josh I knew you would come through. The link you gave was exactly what I was looking for. The coil pack is a Diamond, My readings were 2 ohm that should be 0.7 ohm and 18.5Kohm that should be 21Kohm. Could this cause the car to die or any drivability problems? I'd hate to shell out 75 bucks on a new one with no changes in the car - and should I consider a used one?

#4 Legacy777

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Posted 08 March 2004 - 01:03 PM

assuming you performed the test correctly, the readings should be around those specs.

If the coil pack isn't working right, it can cause a lot of problems.

You can try to get a used one......I got my diamond for like 50 bucks, subaruparts or 1stsubaru should be around that price.

#5 intrigueing

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Posted 08 March 2004 - 03:26 PM

I went out for lunch, and after coming out of the store the car took a while to start, it did not feel like it was kicking, then it started, and the CEL was on. I will get the code pulled soon - however after driving the car back to work there was a humm noise from the rear only when the car was moving - but it was independent of speed, and braking and turning had no effect on the sound. After stopping I crawled under the back (no noise while parked), then I drove it around the parking lot and there was no noise. Could the noise be the fuel pump going in the toilet? Do subaru fuel pumps humm when they are dieing, and would a bad fuel pump set a CEL?

#6 Legacy777

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Posted 08 March 2004 - 07:07 PM

hmmmm....this is the same car correct?

Don't think a fuel pump would set off a CEL. Really not sure what the problem is....check the code and report back.

#7 intrigueing

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Posted 08 March 2004 - 11:14 PM

Ok here is the scoop Josh, yes same car. The back brakes are toast, the wear indicators were making the noise from the rear, odd how problems come in pairs at the same time..... anyway the code was cam position sensor, bank 1. Is bank one drivers side? Going to get one locally, along with pads. I'm gonna hold on the coil - could the cam sensor sound be causing a die at idle and difficult starting?

#8 Legacy777

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Posted 09 March 2004 - 09:20 AM

Anything is possible.....like I said. Is the cam sensor code a steady, always on code? If you reset the computer, does it come back right away?

#9 intrigueing

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Posted 09 March 2004 - 01:04 PM

Reset the computer and the CEL has not come back. The problem is very intermittant and the only clue I have is the cel immediately after the car had trouble starting. I had the cam sensor throw a CEL about 8 months ago - no other symptoms other than the CEL - reset it and never came back till now. I ordered a new one from the dealer for 23 bucks - it'll be here in 2 days. Are there problems with the cam sensors, as I see my car had recall service for cam/crank sensors at 50K miles? Did SOA replace the sensors under the recall?

#10 Cougar

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Posted 09 March 2004 - 02:35 PM

Just reading throught the posts here guys and thought I would throw in my thoughts.

The meter readings you took on the coil look encouraging to me due to the fact that both sides agree in the readings. Depending on the type of meter design and circuit you are measuring the readings can vary some. Shorting your meter probe leads and checking the ohm reading will tell you how much from your test reading you will have to subtract to get the actual resistance of the circuit if you really need to know the actual value of small resistance measurements. The main thing again, is that both side agreed.

It sounds like you do have an intermitant CPS and I don't know any info on TSB's for this. Also, I'm not sure what side is bank one but I think it is the passenger side. Can someone verify that?

#11 frag

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Posted 09 March 2004 - 02:46 PM

anyway the code was cam position sensor, bank 1



That's strange : there is only one cam sensor and it's on the driver's side cam. The fault code I know that would mention something like bank 1 (upstream) and 2 (downstream from the cat) is the one for the O2 sensors.
Just a tought.

#12 Cougar

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Posted 09 March 2004 - 03:31 PM

I was thinking that may be the case Frag but wasn't sure since I have no working experience on these model engines.

Can you tell us if cylinders 1 an 3 are on the passenger side of the engine?

#13 intrigueing

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Posted 09 March 2004 - 04:14 PM

Like frag says there is only one cam sensor. The scanner was a generic OBD II scanner that autozone had, so I suspect that is to blame.

http://www.endwrench...lTestingF98.pdf

This says +- 20% on the terminals and +-10% on the harness, so my 2ohm reading should be a maximum of 0.759 ohms, leading me to think that the coil should be replaced.

The cylinders are arranged

_________ <----Windshield

3.............4

1.............2

So yes 1-3 are on the pass side.

The best price I can find on the coil is 75 bucks from 1stsubaruparts - anyone else find better?

#14 Cougar

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Posted 09 March 2004 - 04:55 PM

I doubt your coil is bad. Did you check your meter lead resistance on your meter like I mentioned in my previous post? It can change your readings significantly, a couple of ohms possibly.

Thanks for explination on the cylinder locations.

#15 intrigueing

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Posted 09 March 2004 - 05:22 PM

The voltmeter has an adjustment to allow you to zero the resistance with the test leads touching. I'm gonna try the CPS first, I'd like to keep the 75 bucks (cost of the coil) in my pocket if I can. Thanks everyone for your help!

#16 Cougar

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Posted 09 March 2004 - 08:34 PM

I think your making the right choice on the part. Be sure to check for a bad connection also to the sensor as it could be just that.

Your welcome for the help.




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