what causes a spark to foul...constantly.

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gixxer750

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k... my number one spark plug keeps fouling...

Car will be driving fine, and then start cutting out on one cylinder... I can boost it hard, it'll clean the plug up, and run fine for a while. Then I come out the next day, and I've got a dead miss.

Compression is around 175 across the board. The plug is not getting oil on it. I start thinking that an injector may be sticking open(RC 720's), so I swap number one and two injectors. Still the same thing occurs on cylinder 1.

I've tried six different brands of plugs, all last about a day. The plug is wet when I pull it out every time(running on a dead miss will do that).

kinda odd I think. Plug wires are new, and I've even swapped coil packs...
 
Boss302

Boss302

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May 2, 2006
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if it were the heat range i.j. it would be across the board cause they are all the same plug it's not that. it would have to be weak spark like a bad ground or something cause i haven't heard of anything like the valvles fouling a plug which technicallly it is not fouling out cause it can still spark if he boosts to clean it off.
 
I

IJ.

Grumpy Old Man
Mar 30, 2005
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If the heat range is marginal and he's been cruising a bit then hammering it it could be down to the difference in cylinder temps.....
(If I remember right High Comp BBC's used staggered heat ranges in certain cylinders to try and compensate for this)

If he has a dud stem seal it could be enough to foul a plug again if he drives easy then gets on it.

Just guessing here ;)

One more thing just occured to me!

How tight is the Cam Belt tensioner?
 
Silvermk2

Silvermk2

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Apr 4, 2005
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Probably running too rich on too cold of a plug. I had that problem when I 1st started with the AEM and was running one step colder. Now I run stock heat range and a lot leaner with no problems now.
 
G

gixxer750

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I tried running a 2 heat range hotter plug in cylinder 1 for shits and giggles... same result.

Cam belt tensioner is done to book spec. I know your getting at having a slight deformation in the cylinder wall for overtightening it.

The valve stem seals were toyota ones, when I built the motor..

The plugs do not seem to have any oil on them when pulled, only raw fuel...

However, with this block and head, on every build... when I run plugs for 7k miles or more, number one has always had slightly more carbon deposits on it than other ones.

I have my coil packs relocated to next to the brake booster... I'm using custom fit accel chevy wires modded to fit the toyota boots and clips. Could it possibly be too much resistance in the >3 ft plug wire on number one?
 
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gixxer750

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yeah... wires are seperated. Its raining right now, and I don't want to go out in it to the shop.

I'd almost bet that resistance may be the issue...

Oh, I can move the fouled plug to another cylinder, rev it a few times, and it will come back in and start firing again and running smooth.
 
G

gixxer750

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gixxer750 said:
. I start thinking that an injector may be sticking open(RC 720's), so I swap number one and two injectors. Still the same thing occurs on cylinder 1.
Click to expand...


One of the first things I tried actually.... but, good suggestion... that would be the logical approach to the problem....
 
G

gixxer750

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I'm sure that would be quite possible.... the intake gasket isn't very old at all, and hasn't been reused... but I won't rule that out just yet.
 
BillyM

BillyM

MK2 + 7M = FUN
Mar 3, 2006
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...you're over the fence in left field. It would equalize out, see it on each cylinder. I'm with Aaron on this one too. I don't trust injectors for nothin'. I'll test them on a whim if I get the chance.

You're looking at a weak spark (would be replicated on the other plug on the coil too though) or a f'd injector. I'd swap the #1 and #2 injectors, see where the problem goes at that point... If it moves to the #2 plug, get those suckers out and tested ASAP. Honestly, I'd have them tested anyways.

From this thread:
http://www.supramania.com/forums/showthread.php?t=42465
Me said:
To get your injectors simply TESTED

Guys, email tim@cleaninjectors.com and let him know you're with the supra community and want your set flow tested only. He is offering this service to us for a near-flat fee of $25. ...those of you outside the US will be more. My turn around time was one week, including shipping time!

He knows what we're looking for and isn't afraid to give an honest opinion (see my first post) and I'll trust him with my stuff from here on out...
Click to expand...

--billyM
 
G

gixxer750

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BillyM said:
...you're over the fence in left field. It would equalize out, see it on each cylinder. I'm with Aaron on this one too. I don't trust injectors for nothin'. I'll test them on a whim if I get the chance.

You're looking at a weak spark (would be replicated on the other plug on the coil too though) or a f'd injector. I'd swap the #1 and #2 injectors, see where the problem goes at that point... If it moves to the #2 plug, get those suckers out and tested ASAP. Honestly, I'd have them tested anyways.

From this thread:
http://www.supramania.com/forums/showthread.php?t=42465


--billyM
Click to expand...

Already did that(swapped injector positions.) I stated that in the first post and again way down the first page.
 
G

gixxer750

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I've checked connections a few times.... and *I didn't find anything*(doesn't mean it isn't there.)

Brand new toyota harness less than one year old.. maybe 6000 miles on it!

I sure don't understand this one...
 
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