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Sputter under throttle.

gvr4ever

Well-known member
Joined
Aug 6, 2002
Messages
6,052
Location
central Indiana
My car has developed a nasty sputter and resistance to go lately. I had this problem last year and new spark plug wires fixed it. I suspect it is a spark problem, but it's been so long since I've had to trouble shoot anything on this car, I'm really rusty.

Are the coil packs prone to going out? Anyway to test them? I have a logger, but I hope I can reload it or get it to work. Its been years since I've used it. AFR gauge is acting normal, no CEL, no knock.

Plugs and wires are new. No new smoking or anything. 14xk miles on a modest driven mild setup, so I hope no engine issues.

What should I check first?
 

gvr4ever

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Aug 6, 2002
Messages
6,052
Location
central Indiana
Google helped me find this, but does anyone know of more detailed instructions for testing the coil pack?

The picture looks like they are using other terminals as ground. That doesn't seem right...
 

jepherz

Staff member
Joined
Aug 8, 2004
Messages
7,877
Location
KC, Missouri
Under what circumstances does it sputter? At high load? Idle? Right after starts? You can pull the plugs and figure out if it's a fuel or spark issue based on how 'dry' and grey they look. Based on your thoughts, they should be more black and wet, but if it was a fuel problem, they opposite would be true. Also, if it's still running but missing bad, chances are just half of the coil pack is going out so the plugs from the tandem cylinders should tell you (1 and 4 or 2 and 3).
 

gvr4ever

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Aug 6, 2002
Messages
6,052
Location
central Indiana
It isn't idling smoothly. Under normal driving boost, it actually feels fine. At WOT it breaks up. So it pretty much sputters under vacuum, starts to feel normal at normal boost levels, and then breaks up if I try and drive aggressively.

I can look at the plugs, but they might not even be old enough to show the truth. If it was a lean situation, I'd think the AFR and knock sensor (keydiver knock gauge) would show that.

I was going to attempt to test the coil pack, but I was hoping for more detailed instructions, but I can't find them. Not sure how testing the resistance is a full test, but I don't really know.
 
Last edited:

gvr4ever

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Aug 6, 2002
Messages
6,052
Location
central Indiana
I did think of that last night. I'll have to see if I can hunt down my home made boost leak tester. Haven't used it for awhile.

Just when you think a GVR4 is reliable....
 

gramkrakr89

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Joined
Jan 25, 2010
Messages
308
Location
Bunker Hill, WV
Quoting gvr4ever:
Just when you think a GVR4 is reliable....



/ubbthreads/images/graemlins/bawling.gif /ubbthreads/images/graemlins/bawling.gif /ubbthreads/images/graemlins/bawling.gif
 

gvr4ever

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Joined
Aug 6, 2002
Messages
6,052
Location
central Indiana
Thanks for the tip. I changed the fuel filter a few months ago. I thought I did a major tune up, but I missed something... Or its just something new. I've been wanting to change the CAS, and have the alt rebuilt anyway. I guess I can just turn it in to a project.

If it is the coil pack, are COPs worth doing?
 

ghostinthevr4

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Joined
Jun 11, 2008
Messages
587
Location
Fresno, Califonia
Also check your power transitor it's a lil black square next to the coil packs. Usually when they go out you'll lose two cylinders but it's worth looking into.
 

Hksvr4

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Sep 22, 2004
Messages
3,023
Location
NYC
^^ This.

If you are changing/changed the coil pack, the transistor should be changed too.
 

gvr4ever

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Aug 6, 2002
Messages
6,052
Location
central Indiana
Mmm, I seem to be missing all of my service manuals. Are they still available on pdf? I've noticed over the last few days trying to find information that many links are dead. /ubbthreads/images/graemlins/bawling.gif

Could someone please tell me exactly where the ignition coil is? Spark plugs look fine, no boost leak. I hope it's spark...
 

gvr4ever

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Aug 6, 2002
Messages
6,052
Location
central Indiana
Okay, hate to nag, but google, vfaq, local search, and youtube are failing me.

The coil pack is the part that the spark plug wires attach to yet? If so, where is the ignition coil?

I was looking at rock auto and they show the ignition coil as the whole pack? Is it a all in one unit, or are they separate? I'm not finding anything that looks like a coil, or the plug in the picture above on how to test the ignition coil.


 

gvr4ever

Well-known member
Joined
Aug 6, 2002
Messages
6,052
Location
central Indiana
Quoting ghostinthevr4:
Also check your power transitor it's a lil black square next to the coil packs. Usually when they go out you'll lose two cylinders but it's worth looking into.



How do I test it?
 

Quoting jepherz:
Under what circumstances does it sputter? At high load? Idle? Right after starts? You can pull the plugs and figure out if it's a fuel or spark issue based on how 'dry' and grey they look. Based on your thoughts, they should be more black and wet, but if it was a fuel problem, they opposite would be true. Also, if it's still running but missing bad, chances are just half of the coil pack is going out so the plugs from the tandem cylinders should tell you (1 and 4 or 2 and 3).




+1
 

gvr4ever

Well-known member
Joined
Aug 6, 2002
Messages
6,052
Location
central Indiana
Update

Out of desperation, I changed the coil pack. Not a bad thing to do on a 20 year old car...

Anyway, nothing has changed.

The car smells rich and sounds like a subie boxster engine and has a delay when hitting the gas.

It does smell very rich.

Plugs are too new to be wet. They all look exactly the same. Spark plug wires are new too. I double checked the base fuel pressure to be sure, and that was fine.

Any ideals?

Sadly, I need this car up and running very soon. I'm down to one car. Eeek.
 

gvr4ever

Well-known member
Joined
Aug 6, 2002
Messages
6,052
Location
central Indiana
I did find a leak some place in or near the intake manifold. I started a new thread under technical.
 
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