Smashed plug on cylinder 4 under boost only

[Edogg6565]

I have a fully built 1g top and bottom with a 60 trim turbo on 23 psi. The car runs and drives fine under normal comditions but when I do a pull in boost is smashes the plug on cylinder 4. Car ran fine during tuning and now does this. If I drive it normal it drives fine all day long. It will only smash it under boost. What could cause this as the motor has no knock or anything.

Engine is knife shaved crank, eagle rods, arias 9-1 pistons, hks cams 264/272, ti retainers, dual valve springs and so on. It's tuned on aem ems.

 

[keveka2]

have you replaced the plug or tried another one and what does the #1 plug look like

 

[Edogg6565]

Plugs 1-3 look fine and I replace it and car runs fine till boost again then it mashes it shut and starts miss firing on cylinder 4 as there is no gap.

 

[keveka2]

does it look like it has been hit by the piston... just another though are you sucking in any air through a leaky gasket or seal causing that cylinder to run hotter than the rest..

 

[Edogg6565]

Not really. Doesn't look like anything hit it.

 

[Lou98GSX]

try putting an extra washer and see if it still happens

 

[miguelmcv]

Any pics of the plug?, a pic will tell more then what you can explain.
Post a pic so we all can see it.

 

[Edogg6565]

Plug

 

[rbwtrans]

How many times has this happened?

 

[Edogg6565]

Twice.

 

[dondadda]

dude, check out your ecu. when my friends car did this, his computer was bad. something about the drivers in the injector system.

 

[rbwtrans]

What plugs are you using? Brand and part #

 

[Edogg6565]

Fist set was bpr6es ngk and second time was ngk bpr8es

 

[hotrodssnova]

Are you using a NEW plug or one you have re gapped? It looks like it was burning good, but how long did you drive it before you pulled it? Were the 2 "smashed" plugs from the same batch of plugs you bought?
Wonder if it's leaning out and getting so hot, when you go into boost, cylinder pressure is pushing it closed.
I would go to a differnt parts store and get 1 new plug and try that. Could be a bad batch of plugs and you happened to get a couple.

 

[dondadda]

not the injector system, but the ignition system, sorry! I know you don't want to hear that, but we troubleshot this car to oblivion and believe me, the only thing that fixed it was a (NEW ECU). Take a look at the top of your piston with a flashlight and see if you have knick on the top of your piston, this is what started happening to his piston as well. Good Luck!

 

[awdtalon4451]

Twice.

Weird!! If it was making contact with the piston #1 would have the same problem. Can't say I've ever seen or heard of this. Maybe one of the guru's can chime in on this.

 

[Edogg6565]

2 different batches of plugs. All were new.

 

[BogusSVO]

You are running lean.

The ground strap will curl up like that.

Have the fuel injector checked out, could be a partial clogged filter basket in the fuel rail side.

Simple test swap that injector with one of the cylinders that is not giving an issue and see if it follows it

 

[rbwtrans]

These cars use a waste spark type of ignition system. Swap wires 1 and 4 at the coil (same coil) and see if the result moves to #1 or if it stays at #4. This should help you narrow it down to ignition or a cylinder issue.

Dale. Youand I were typing at the same time . I had the same thought. My idea was to shoot down the ignition system first,since it's easier to do.

 

[BogusSVO]

Rick... Glad to see you on the board!!

I would agree to check out the ignition, but he says it happens under boost only.
But I understand the logic you used and I would tend to agree if it was all the time.

But if the injector is only flowing say 80% of what it should, it would not make much of a differance in off boost driving, but when in boost and the fuel demands are high, the partial clogged injector would compound the problem.

 

[dondadda]

checked the top to the piston yet? do you see any damage?

 

[Edogg6565]

Can't see anything on piston. Am going to use a bore scope Saturday and see.

 

[delta448]

I agree with Dale and also would suspect the injector first. Was the car tuned on E85?

 

[Edogg6565]

No. It was tuned on 93 pump gas.

 

[Edogg6565]

Seems to be a partially clogged injector on cylinder 4. bore scope was clean with typical carbon on pistons but no marks in cylinder on on piston top. So injectors are sent off to be cleaned and flow tested.