Low power - Coil pack or DIS module or both? (pulled codes)

[Arjun]

The car: 1989 SHO with heads rebuilt 8000km ago.

For the past couple of months, at idle there's been an occasional misfire-- nothing significant enough to make me want to pull the codes.

Today I'd driven to school, parked for a couple hours, then I headed home. I left the parking lot, and my car felt the way it normally does. A minute or so later, I pull up to a left-turn light behind a Mazda 323. As soon as we turned onto the highway, I was going to whip past it.

...Except that I noticed that the car was sounding funny and my idle speed had just dropped a couple hundred RPM. Damn SHO, giving me problems again. ...So the light goes green, I start driving, and there's low power-- feels slower than my mom's car! I pull off the road, check in the engine bay, everything looks normal, exhaust smells a little gassy. Remembering a couple years ago when my spark plug wells were filled with oil, I pull the plug wires individually, and they're clean. So I fired the car up, and cruised home slowly.

Get home, pull the codes. KOEO tells me I've got a stored code 46 (coil 2 primary circuit failure). KOER gives code 11 (no problems found). Cylinder balance test shows problems with cylinders 3 and 4.

From here, I'm not sure where to go. I just called up the parts place that I deal with most often, and a coil pack costs CAD$153, DIS module CAD$165.

I'm not sure which of those two are the most likely culprits-- any suggestions? Anybody have any idea how to test one or the other?

Thanks for any help you could provide!

 

[projectSHO89]

I just posted a link to a "How to test the Coil Pack" yesterday morning.

http://www.shoforum.com/cgi-bin/ultimatebb.cgi?ubb=get_topic;f=17;t=005873

Steve

<small>[ March 10, 2003, 04:39 PM: Message edited by: projectSHO89 ]</small>

 

[MOSHO92]

I had this problem once. Mine turned out to be the DIS. If the computer throws unlikely codes and you get different cylinders on the balance test each time, ny guess would be the DIS. Easiest way to check is to swap crossover tubes with another healthy SHO.

 

[Arjun]

Looks like it's my coil pack; the DIS is sending signals out to all 3 coils, but I get no volts on the terminals for cyls 3&4.

Edit: earlier when I did my KOER test (I messed up twice, third time it worked), I ran the cylinder balance each time, and each time it came out with cyls 3&4 being bad.

I'm impressed at how well my car's running given that it's only running on 4 cylinders-- it feels like it's got as much power as my mom's Jetta, it's surprisingly smooth inside the car, and it's surprisingly smooth when accelerating. ...Not that it's as smooth as usual, just that it's smooth considering it's missing on two cylinders...

Thanks for the help!

<small>[ March 10, 2003, 05:36 PM: Message edited by: Arjun ]</small>

 

[revhardSHO]

I'm impressed at how well my car's running given that it's only running on 4 cylinders-- it feels like it's got as much power as my mom's Jetta, it's surprisingly smooth inside the car, and it's surprisingly smooth when accelerating. ...Not that it's as smooth as usual, just that it's smooth considering it's missing on two cylinders...

Thats yamaha for ya! thumbs_u

good luck!

 

[RStalveyARFF]

yeah, cylinders 3 & 4 would run on coil #2 so it definitely sounds like a coil pack.

<small>[ March 10, 2003, 08:37 PM: Message edited by: SHO91MTX ]</small>

 

[Arjun]

Mmmkay, so anyway, after chug-chugging my way to my auto parts people across town, I buy the new coil pack, hop in my car, fire it up, and as I drive off I realize that it's come back to life and I've got full power.

Just swapped the new coil pack in; perhaps the coil pack was giving low power for a while earlier, because it feels like I've got more power now than I did yesterday or the day before. Who knows, maybe placebo effect, maybe real effect. I'll have to go driving later today. Dinnertime now, tho.

Thanks for the help!

 

[RStalveyARFF]

yeah, your butt dyno isn't the most finely calibrated instrument wink

 

[Arjun]

Noooooooooooooooooo!

After 150km of driving, I just dropped a friend off, and as I pulled up by his place, I noticed that my idle speed was low, then it chug-chug-chugged as I drove off! argh!

Crap, I'll have to bring my multimeter to school tomorrow and check around under the hood between classes in the afternoon.

Crap, crap, crap.

Crap.

Crap, and I've got to get my car fixed by Thursday afternoon-- I'm (supposed to) leave for a weekend trip on Friday...

Did I say "crap"? I meant it!

argh!

 

[brandon]

hey my 89 is doing the same thind driving fine pulled into mc ds an eat came back out an started it an it sounded like shit ran good in all but ne it was missfireing what the **** put new coil on an doing same thing new plugs an wires also what could it be

 

[brandon]

hey my 89 is doing the same thing driving fine pulled into mc ds an eat came back out an started it an it sounded like shit ran good in all but new it was missfireing what the **** put new coil on an doing same thing new plugs an wires also what could it be

 

[brandon]

well i have the same problems put new plugs wires coil dis module and the same thing is happening what could it be no codes are showing need help asap

 

[Arjun]

brandon:
well i have the same problems put new plugs wires coil dis module and the same thing is happening what could it be no codes are showing need help asap

In my case my problem's intermittent, and since my post the other day my SHO's been working perfectly-- I've got to wait for it to fail again to diagnose my problem further. In my case, since I was previously able to confirm that a signal was making it as far as the electrical connector to my coil pack, that tells me that either the problem was with that electrical connector or else the problem was with the coil pack. I replaced the coil pack, but that didn't solve the problem, so now I'm suspecting my wiring or teh connector.

Brandon, have you taken a voltmeter to the wiring to see if you have power getting as far as the coil pack?