Blown Plugs and it still works?!

[caminperth]

Man these RB engines are strong! The story goes...

Had it tuned Sat morning. All the air/fuel ratios were right and it made good power for stock turbo and cooler - a tad under 260rwhp.

It was a beautiful day and after having a bite to eat - my arm was twisted by a certain whore expert to go for a drive so we decided to drive up to Chittering...

After a gentle cruise up the freeway and a meander up towards the pine plantation near Wanneroo raceway, we turned off toward Great Northern highway and started passing some slower cars (which just happened to be all of them:D).. After a nice run I was onto the final straight and doing some good revs in 5th when something let go and I lost power... "hmm" I thought.. "wonder whats wrong?"...

We pulled off - inspected my engine which seemed to have a slight miss, decided the plugs had finally given up and decided to continue on and pick up some new plugs on the way home.

After a nice drive out to Chittering, back via Joondalup and through to my place in West Perth, everything was running ok with the exception of a slight miss.. My baby idled itself down in the garage and the whore expert and I went to work to replace the plugs...

What I saw next nearly gave me a heart attack... Somehow numer 5 plug had lost most of the hook over the electrode.. it just seemed to have melted away... "hmm.." I thought "wonder what the others are like.."

Number 3 was the next casualty. All I can say is that it had been obliterated... the hook over the electrode was completely missing and the electrode itself looked like it had suffered some sort of explosion as it was missing down to about 10mm inside the plug...

Panic stations were manned and calls were made.. I ended up replacing the plugs and turning it over.. Everything ran ok with a slight miss at idle - nothing more.. I let it be and decided to limp it up to a garage today...

Enter the compression test this afternoon. I would definitely recommend the Ultratune in Warwick. Dave the mechanic who works there is an absolute champ..Anyway - I digress.. So we pulled out the plugs (that were quite white) and attempt to do a dry compression test and it turns out his new guage is broken. Never fear, you could actually hear the difference between the compression in the other cylinders to number 3 cylinder. Then we try a wet compression test and it seems to come up ok. So we bolt everything back together and do an emmissions test on it. This showed excess fuel/oil which would indicate a tired engine. While it was idling, there was an arcing noise coming from under the plastic cover over the coils which seemed to coincide with the missing.

All of this tells me a few things:

1. The white plugs (100kms old) tells me that it's running lean

2. The wet compression test tells me that number 3 is low and that the rings are possibly to blame

3. The arcing sound tells me that one or possibly more of the coil packs is doing something it shouldn't

So after all this I gave the car a right caining, as it desrved no less, and everything was fine. Aside from the missing at idle, everything else seems in working order...

Plan of attack:

1. Talk to the tuner and possibly run it up on the dyno again to find out why it's running lean.

2. Get an endoscope and check out the damage to number 3 cylinder.

3. If not too bad - thrash the car like normal.

I'm thinking that the low compression has always been there and I'll fix it when I get round to doing a full rebuild..

Comments? Opions? Have I reached the completely wrong conclusion? Help is needed...

Cam

PS - if you got this far - thanks for taking the time to read it!!

[APA]

rebuild time coming fairly soon then eh?

adrian

[drifta]

lets hope its not to bad

[caminperth]

Nope.. I'm thinking that a bit of low compression in one cylinder is something I can live with for a while.. What I am worried about is why it is running lean when the fuel ratios were ok on the dyno...

[rob77]

Ever since I ran up more boost I've had a problem with the car misfiring. Its not all the time just now and then, pulling the plugs out and looking at them doesnt really show the car running too rich, although the dyno's AFR says different. I'm thinking my missing issue could be something simular to cams.

[caminperth]

Rob - I am almost certain the missing issue is due to an arc in the coilpacks.. I can hear it at idle.. Wondering if I should just replace the lot of em to be certain..

[rob77]

I cant hear any arcs on mine at idle, at least I dont think so.

[Micko]

You sure it's an arc cam?

The injectors are quite noisy in our engines & mack a ticking/cracking sound that could be mistaken for something unsavoury...

[Micko]

Cam - if it seems to be one of the coil packs - disconnect it when the engine is idling to see if the noise goes away

[GTS500]

if you melted a spark plug end i would be checking the air fuel mix this tends to be a severe warning that you are running too lean,the next sign would be cooked rings resulting less compression and or a hole melted into the top of the piston,i have seen this happen before and it's easy to avoid.Check the fuel pump and pressure reg are still working correctly,if so ask tuner to recheck air fuel ratio are correct.Good luck and i hope this helps.

[caminperth]

Thanks guys for the input so far..

Micko - yea - it ain't the injectors.. definitely coming from under the plastic cover.. quite loud..

GTS5000 - when i pulled the plugs today - all were white so something has leaned things out.. not sure why it would've changed from the settings on the dyno tho.. am going to get the ratios checked again asap...

[GTS-t VSPEC]

Cam, Can't remember twisting your arm to go:p I was amazed the car could drive with the catastrophic damage the plugs had taken. Still seemed to drive quite well considering. Does it stall on idle now or not?

[caminperth]

It was still doing the stall thing when it tried to come down to idle.. Once the idle stabilises it seems to be ok..

oh yea - I'm not trying to blow it up, but a bit of low compression isn't a worry. What is a worry is the fact that it's running lean and the coil packs are arcing.

[N I B]

The cars not lean modern EFI cars keep their plugs clean the worry is why the problem is only on the 2 cylinders .

The ITC may be the problem so i think it should be checked out before the engine is destroyed.

[caminperth]

So the white on the plugs is normal Steve?

Why do you think the ITC would be the problem?

Can you PM me when I can come in to get you to have a look?

[GTS-t VSPEC]

Cam, Just phone Steve, he's only on the net in the morning and evening.

[caminperth]

Paul - am sorted for Saturday morning...

[GTS-t VSPEC]

Cool. What was the compression in each cylinder?

[caminperth]

Paul - the guy's guage was broken so we didn't get a reading - only differences between the way each cylinder cranked over.. all of them except for number 3 sounded tight..

[GTS-t VSPEC]

Hmm, I think you might want a better result than that. Can you go back once his gauge is fixed?