SeniorXJ

The other day my 98 limited started running like crap right out of the blue. Long story short, #5 cylinder had zero compression, brought it to my mechanic, & it had a broken valve spring & possible burnt valve. They say it may be due to the E3 plugs I had in it. They sent the head to the machinist & that's where we stand at this time.
Has anyone had any experiences like this???

BMAC6642

I've been using E3 plugs for years in 5 different vehicles and have had only 1 plug go bad but no damage to the engine.

cruiser54

Nah. I'm not buying that.

I woulda just put new valve springs in it without removing the head.

abodyjoe

did he say how the e3 broke a valve spring? i find that hard to believe.

SeniorXJ

It's extremely odd to me also that a plug could cause this hence the thread! When #5 had no compression I assumed a head gasket since it's common for the newer models to blow there. When he told me the valve spring was broke & a possible burnt valve, it was in a voicemail cause I was unavailable so we haven't spoken & its now thanksgiving.

I have a ton of questions myself, so before I become a disgruntled customer in a 4x4 shop I figured I'd start a convo here on the matter. These 4.0's are built well & broken valve springs are not common in my opinion.

Turbo X_J

Gimmicky spark plugs won't cause a valve spring to fail.

SeniorXJ

So if a misfiring plug in just one cylinder couldn't cause a valve spring issue then what would?

Remember this problem happened out of the blue. No issues running, no idle issues, nadda. She did have a starting issue caused by an engine computer that was replaced 2 months ago along with 3 censors.

cruiser54

Metal failure.

SeniorXJ

Which is extremely uncommon in the 4.0 motors.

cruiser54

This is happening:

abodyjoe

if a cyl was misfiring then i would think you would notice it not running right..

nujeepguy

a question keeps coming up, just how mechanically could a plug cause a broken spring. im thinking it would break under spring compression, max pressure. how would a plug make this worse?
i cant make sense of it. doesnt seem to be a connection.

SeniorXJ

Figured id end the thread with an update. There really is no direct reason for the valve spring to have broken other than bad luck. The head gasket was starting to go and the head was warped. As for the E3 plugs, I attached a photo to show what they look like after only 8k miles! Stick to NGK's in these motors!!

Turbo X_J

Check the coolant temperature sender?

Waynerd

Wasn't it 97-99 that the 4.0 had weaker valve springs. And also with all the carbon on the plugs it's possible weak valve springs could cause a lot of buildup. Did you change all springs or just one?