[dreslion]

Pros!

Hey I have a quick question that has been puzzeling me for a while. I have a Vortec V2 HO S/C on a 4.0 V6, recently changed the ignition coil because the 5th cylinder stopped getting spark. 1 week after that when the car was under high boost it misfired and the read was Cylinder 5 misfire. Checked the spark and it was still good. Pulled the plug and saw that piece of the ceramic was broken off and the head (tip was pushed onto the electrode closing the gap). I put in a different plug, but since then I hae had to change plugs about 4 times on just that cylinder. As far as I know, nothing fell into that cylinder, but does anyone have any idea what can cause this? I am confused. I had an earlier post regarding this because the suggestion I got was to port and repolish my heads for that side or just change them altogether. Either way, that is +$2k on an engine that has never given or showed signs of physical damage before. Any idea what it might be?

Also, my plugs are gapped at .04 and i was thinking about dropping them to .03

Signed,
Confused and Frustrated Stang owner w/ a pony that limps when it gallops....

[SSteady98]

maybe some shit was about to blow. can you turn the boost down on those things?

[mustanginky]

You likely went lean, detonated, and broke a ringland. Get a borescope or a flashlight and look at the piston. I'll put $5 on it that's what happened. Does it look like metal to metal contact caused it?

Reason I say this is I've been there and done that. Time for a rebuild.

[99 BLUE V6]

I agree ^ if you cant get a bore scope do a leak down. then prepare for a tear down.

[ESG-642T]

How much power was this car making?

[mustanginky]

I'd say prepare for a full teardown and rebuild anyways

[dreslion]

This problem was only affecting Cylinder 5 that last 6 times that it happened. Last night I noticed a misfire and assumed it was Cyl5 again (the reason I posted). I checked today and Cyl5 is fine, BUT Cyl 3 AND 2 now are the cause of the misfire and have damaged plug heads. Cylinder 2's tip was bent slightly to the side. Cylinder 3's plug had a bent tip (gap closed). WTH?!?! I was assuming that something was in cylinder 5 that was causing the problem, now I'm not too sure. Could plugs that are running too hot do this?

It's a stock ignition with a recently replaced ignition pack and factory recommended AGSF 24N Motorcraft plugs gapped at .04

[dreslion]

I think you guys are right. I was hoping to get it ready for Mustang Magic's dyno, but now it just looks like I'm going to have to eBay 4.0 heads...

The car was supposedly making about 350 rwp, but capable of 400 after the dyno. I'm considering forged pistons when i rework the top half of the engine

[dreslion]

Haven't seen signs of compression loss yet, but cylinder 5's spark plug does look like they were being damaged from metal to metal contact. The bore scope showed signs of a scratched piston...

I think a well planned rebuild is coming... This after just dropping $5k in work!

[ESG-642T]

This is why I do my own work.

[dreslion]

@ESG-642T: I hear you and fully agree. Didn't have time and am about 10yrs stale in being a gear head, but that's all about to change! After changing all 6 plugs with NGKs gapped at .03 I saw that Cyl 1 might have a sleeve or was rebored by the last mechanic that did the plugs on the car... Only could change the 5 so I regapped it, Great!

[mustanginky]

If there's metal to metal contact, you have a broken piston. I lost ringlands on two pistons but still had compression on each cylinder despite the rings being gone. Good luck and sorry to hear.

[99 BLUE V6]

YOU NEED TO PARK IT NOW. before you cause more damage.changing plugs at this point is just wishfull thinking.

[ESG-642T]

Just curious, was this car tuned at all? Or just kit installed and been running?

[SSteady98]

ouch hell well they definitely know what it is, lol. was just pitching my .02

[chocolate]

Originally Posted by dreslion @ESG-642T: I hear you and fully agree. Didn't have time and am about 10yrs stale in being a gear head, but that's all about to change! After changing all 6 plugs with NGKs gapped at .03 I saw that Cyl 1 might have a sleeve or was rebored by the last mechanic that did the plugs on the car... Only could change the 5 so I regapped it, Great!

Just an FYI since i see you don't post here much. There is a little button to click in the lower right of all posts that says "quote". Press that and it will quote like above. if you want to quote/comment to more then one post there is a little button next to that that will turn red. When you select several people the last person you can hit the quote button or just hit post reply.

Just an FYI to make your life easier. I don't even have a mustang but check these threads to learn faster.

Good luck and have a good day.

[slater]

sounds like everyones claim that FI is perfecrtly safe for these engines is wrong

[i-bought-a-v6]

Originally Posted by slater sounds like everyones claim that FI is perfecrtly safe for these engines is wrong

That's true it's only safe for 3.8's, but seriously cars that aren't supposed to have FI will have problems with it.

[mustanginky]

As long as it's well maintained, tuned and driven respectfully and at a safe boost level, no reason it shouldn't run for a long time. Sounds like the op isn't too sure about the tune. It could have gone lean/been lean and finally gave up the ghost. Time for a v8!

[dreslion]

No, I'm not sure about the tune at all. I was scheduling it to be tuned at MustangMagic in a couple of months.

The last mechanic did an engine flush and said I should be ok until then as long as I drove the car carefully and not over 60 mph or high rpms.

I appreciate your thoughts:

What is the danger in driving it carefully for the next couple of months? Can't afford the engine work until Jan, which now looks like I will be oing both engine and dyno...

(thanks for the reply tip, but the "Quote message in reply?" option is grayed out for me