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Old 10-04-2004, 09:26 AM   #1
Seeinstars
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Default install cams and flywheel, now a bad misfire at idle.

I just installed techworks engineering stage II SOHC, the twe valve springs, an exedy lightened flywheel, and sti headgaskets (there thiner then the 2.5 n/a gaskets so theres a little bit of compression gained. It runs very strong but at idle it misfires really bad and will throw a code on all 4 cyls. for a misfire. I was wondering if its from the duration of the cams being too long for idle, or the flywheel being too light and the idle air control valve not being able to keep up with it.
Just wondering if anyone has had any similar problems? I been a tech at the subaru dealership for 2 years and am very firmiliar with these engines but I just wanted to see what some other people think. So far I think its the duration of the cams and the valve not closing fast enough at idle. But it could be the flywheel too. TWE says that there cams are not quite enough to throw a code at idle.
thanks for any info.
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Old 10-04-2004, 11:14 AM   #2
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i have an exedy lw flywheel without aftermarket cams. (although soon to be cobb stage 2). I have never had a cell from the flywheel. Never had any misfire cells in general.
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Old 10-04-2004, 01:29 PM   #3
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you went with NA cams, they are gonna miss at idle, high lift w/ lots of overlap=bad for idle quality
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Old 10-04-2004, 01:36 PM   #4
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Seeinstars - It's not very likely it's from the duration of the cams since looking at the info on TWE's website; the duration is only slightly more then stock. A couple of local guys who have these cams don't have any missfire or idle issues. Have you checked to see if your coil pack or your ignition wires are still good?
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Old 10-04-2004, 05:16 PM   #5
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Quote:
Originally Posted by GTBGUY
Seeinstars - Have you checked to see if your coil pack or your ignition wires are still good?
I think I've figured it out. its between the lightened flywheel and the lightened crack pulley I forgot I had. The crank is just way too light. I'll put the stock pulley back on and see if that solves the problem
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Old 10-04-2004, 07:15 PM   #6
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A lot of cams will throw misfire codes even when the manufacturer says they won't (TWE for example). From what I've read this is normal and to be expected, and even though you are getting a misfire-related CEL, it does not mean that the engine is actually misfiring.
I have an Exedy lightened flywheel and an Unorthodox Racing UD pulley and I don't get any misfire codes.
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Old 10-04-2004, 08:03 PM   #7
Seeinstars
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I remember a couple of months ago I put a flywheel and pulley on a 02 wrx, and the same thing was going on with it. I didn't really missfire but couldn't idle right so it throughs a missfire code.
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Old 10-04-2004, 08:44 PM   #8
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if your timing is off, even just a hair, it would be enough to misfire the cylinders at idle with an aggressive cam. i would start there,
second, it might not really be missing, the extra comp. you have by adding the sti head gaskets could be really throwing them pistons back a lot harder than they should, again with an aggressive cam its very possible,

i had a 268 cam in a 2.0 vw motor and the timming was retarded (for the nos ) and at normal idle speed 750rpm, you would think it was running on 1 cyl. i had to up the idle to 1100 so it would be smooth

Last edited by robsgotit; 10-04-2004 at 08:50 PM.
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Old 10-04-2004, 10:10 PM   #9
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that makes a since too. Well tomarrow I'll try by taking off the lightened crank pulley and putting the factory back on. I'll start with the simplest things.
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Old 10-04-2004, 11:13 PM   #10
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Does it actually idle rough, or just throw codes? Those TWE cams shouldn't affect the quality of your idle at all.

Are you sure you got the timing belt back on correctly? I know your a tech, but that's the first thing I'd check - sound like your off by one gear tooth.
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Old 10-05-2004, 07:24 AM   #11
Seeinstars
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I am pretty sure it's on there correctly. I had everything perfectly on the timing marks, and I've never had any of my customers cum back with any timing problems.
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Old 10-05-2004, 09:38 AM   #12
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Quote:
Originally Posted by Seeinstars
I think I've figured it out. its between the lightened flywheel and the lightened crack pulley I forgot I had. The crank is just way too light. I'll put the stock pulley back on and see if that solves the problem
Yes... I've seen this happen on many local cars. You can have one or the other, but not both.

Hope that does it for you.
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Old 10-07-2004, 08:54 AM   #13
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I installed a sti crank pulley on yesterday(its a bit heavier then my stock one) and that didn't fix the problem.
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Old 10-07-2004, 09:11 AM   #14
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I have LW GFB pullies along with the exedy lw flywheel i mentioned earlier and i have not had a cell from having both. Are you sure your car is misfiring? I know that with cobbs stage 2 cams a misfire cell is expected. How does it drive? any one know the ways to tell if a car is ACTUALLY missing? would it be 100% apparent? I will be installing Cobbs spicey cams soon and will most likely be dealing with the same issues as seeinstars.
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Old 10-07-2004, 11:25 AM   #15
Seeinstars
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Quote:
Originally Posted by Pat L.I.
I have LW GFB pullies along with the exedy lw flywheel i mentioned earlier and i have not had a cell from having both. Are you sure your car is misfiring? I know that with cobbs stage 2 cams a misfire cell is expected. How does it drive? any one know the ways to tell if a car is ACTUALLY missing? would it be 100% apparent? I will be installing Cobbs spicey cams soon and will most likely be dealing with the same issues as seeinstars.
I just cleared my memory again and it seams to be doing better at idle now. I didn't clear it yesterday after I put the different pulley on.
You can hear it missing at idle but thats because the iacv can't keep up with how fast it revs up and down.
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Old 10-13-2004, 06:35 PM   #16
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Doesn't the ECU throw a misfire code when the A/F ratio are freaking out too?
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Old 10-13-2004, 07:47 PM   #17
Seeinstars
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Quote:
Originally Posted by dpjef
Doesn't the ECU throw a misfire code when the A/F ratio are freaking out too?
It says that it runs really rich when it starts missing at idle.
I still haven't found it yet. I haven't touched it since friday though. I'm going to try a different set of plug wires.
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Old 10-14-2004, 04:05 PM   #18
Seeinstars
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changed out the spark plug wires and it seams to be doing the trick, comes to find out the old wires didn't reach the plugs all the way and made the missfires. It didn't do it before because the cams make it more prone to throw codes because of the bigger load during idle then with out the cams.
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Old 10-14-2004, 05:36 PM   #19
Seeinstars
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didn't fix it, it lasted a little longer this time, it lasted long enough to do a drive cycle and to pass instpection, but then it started throwing missfires again, Ill try putting a hotter plug in it and see what that does.
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Old 10-15-2004, 12:42 AM   #20
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Quote:
Originally Posted by zzyzx
Does it actually idle rough, or just throw codes? Those TWE cams shouldn't affect the quality of your idle at all.

Are you sure you got the timing belt back on correctly? I know your a tech, but that's the first thing I'd check - sound like your off by one gear tooth.
Are those the cams you're running, Steve?

Jay Storm
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Old 10-15-2004, 01:35 PM   #21
Seeinstars
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Quote:
Originally Posted by Storm
Are those the cams you're running, Steve?

Jay Storm
yes there the twe stage II sohc.
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