Sympton of blown HG - boosted 4AGZE

[EldarO]

firstly, find out if its blown first.

before you go ordering parts.

the TeeKay test will let you know for sure, although another test would be to simply check if its munching through coolant.

youll also find that if its BHG, its plow white smoke out the arse end of the exhaust when you drive it home.

i wouldnt be so quick to suggest its BHG, it may just be an electrical problem, something couldve just come loose, or your plugs might have ate shit and died...

Eldar.O.

[30psi 4agte]

From my experience 4a s will mostly blow between cyl no.2 and 3 cause of the gasket thickness there is quite thin between the bores and with extra boost it can simply push the gasket out.
On my motor i also have probs with it going at the back of cyl 4. This seems to be the most common place on mine not sure why mabe to do with a hot spot?
I have instaled a water bleed there to get rid of all the air from the back of head when bleeding coolant

AnywayI would suggest a steel item like a HKS one next they are very Gutsy gaskets.

[nick.parker]

---The plot thickens---
I just finished work. Went down and cranked car. It started and went to a perfect idle on all four cylinders WTF? Since I checked all sparks, I just don't get it. Why would say 2 & 3 not have enough fuel or whatever earlier? I am going to check compression and spark plugs after I get home.....it just makes no sense at all...none at all.

The problem started this morning as I arrived at work. I looked at the car at lunch time it still had the problem. Now at 5:00 it starts and runs???? Place your bets on what the problem is? Non closing completey exhaust valves or something? two sticky injectors? beats me.... May a coil driver getting too hot and firing early to protect itself (but at lunch time the car was cold).

BTW Thanks for all the suggestions so far.

[slide86]

i also wouldnt condem the head gasket straight away.

have you topped up the water yet? is it low? it will go down pretty quick if its not mixing in the oil

how bout spark plugs, leads, fuel pressure, igniter, dizzy.......

all these things are much easier to check and confirm that they are ok before you go pulling the head off.

It would suck to do all that work for a smaller and easier fix!

[30psi 4agte]

Think carefully about EXACTLY what you touched after lunch?

My bet is on Coil or dodgey /loose wire to it.

[jeffro ra28]

Likewise eldarO,
What is the firing order on those things? you may find that it nearly stalls at idle when some plugs are disconnected because 2 and 3 fire next to each other? Im not sure on that one its just a punt.

I see it like this tho, I know from experience with engines EVERYDAY exposed to low threshhold to these problems that it takes a shitload of water to hydraulic an engine. Also, the HG isnt just going to SUDDENLY blow. If it has just started to make the sound then my guess is that it has been deteriating for a while now. So i THINK it would be safe to drive 30km, home. Alu heads however will sink the bridge between cylinders if it is exposed to BHG between cylinders for some time. Which will require a surface grind.
Although 30km of easy driving sounds quite safe to me.

[30psi 4agte]

I just had a thgought! I have had this prob before.May not be your answer though

How are the injectors wired? I.E No2 and no 3 together? I had the connection to the main injector trigger wire ( i trigger two injector off one wire) come loose.

[nick.parker]

I did a compression test, I had almost exactly 12bar on all cylinders +/- FA!! I then took the plugs out checked the gaps, all were 30", cleaned the plugs with wire brush and petrol, put em back in, then I took it for a cane on the open road and it it was fine.

The spark from those stock MAP ZE coils (with custom ignitors running 4msec of dwell) is amazing! As I unplug the lead the sparks are shooting across all over the place to the nearest metal (vally cover).

This afternoon when I was checking each cylinder, I would pull a lead off and hold it to a metal bolt so I would be running on three, not two cylinders as jefro ra28 mentioned. It seemed to be just number two that was weak. I am wondering if I have dodgy plugs still though. And am still a little surprised at the days events! It still doesn't seem to add up - and the misfire was so sudden and independant of revs / boost.

I should just whack a new set of plugs in, sit back, and wait to see if this strangeness happens again.

Cheers, Nick.

[RonRob]

Had something similar except it affected 1,2,3, while number 4 had more then ample mixture on the plug. Problem was my fuel filter and believe it or not it can cause a nasty idle and other bad problems if something came through.

Also, I had a bad idle and jerking on accell that ended up being a bad coil in which one of the terminals on the coil where the lead plugs in was corroded like a battery.

Just my 2 cents

Keep us posted
Ron

[Ben Wilson]

Nick - Have you got a wideband?

I'd be dropping in new plugs and keeping an eye on the mixtures for the next few days if I were you..

[nick.parker]

Hi Ben,
Yep, I have got a Wideband. It was reading normal for idle (0.95 lambda) wierd.....yesterday when it was v8-ing.
One thing however with widebands is that raw petrol vapour can make a wideband read strange values than might just happen to appear normal, it is a known phenomenon.
I wil be logging my drive to work this morning (and hoping my car doesn't play shenanigans again).
Cheers, Nick

[takai]

Yeah, i had my GZE do that a couple of times to me. The first one was a minor vac leak from a vac hose popping off, and the other was the fuel filter giving me the nod that it was dying.

On the second one i replaced the HG anyway.