Asneaky4

Ok..My car is sick and idles rough. Two cylinders are between 40 and 60 psi.. they won't hold enough pressure to trouble shoot. The heads are coming off, but I thought you may want to guess what the problem is.

I know I am suppose to have between 170 and 190 lbs for each cylinder. I have had intermittent "random misfire" problems over the past few weeks. I drive the car very hard (6000+RPM every gear) and I am supercharged (8-10.5 lbs of boost). I have had some detonation at high RPM's but not that much it is hard to hear at 130+mph. I run 92 octane gas at all times. The car has run REALLY well and then poorly.. then well again, now it is very sick and I have taken it in to a "real" mechanic. Do you think that I burned a few valves, blew a head gasket, or have piston damage?

eharleq

Broken rings? Any smoke?

Asneaky4

IF any it would be darker.. from letting it load up.. I know it is not burning all the fuel

zain

Let me know what this turns out to be, as I also have the G2. But then, running it past 6K is pushing it more than I do. (Why 6K plus anyway the power curve falls off after 5300...?)

My guess is you've blown some rings. Any detonation out at the limits is a bad thing. Lucas managed to bend a piston rod this way I think. So it could be worse than just some rings.

I'm assuming you went with some colder plugs, as you can have trouble with our supercharger and the stock plugs if you drive it hard enough.

Audiboy

or the head itself.

If not, could be leaky valves only. Reason is you don't appear to have any symptoms of cracked pistons, piston rings, rods, etc.. since no smoke, no clankety sounds? No water in oil or vice versa? No excessive blow by - i.e. take off oil filler cap and listed for excessive psshh

Now, if it were the head gasket, It may not have been damaged by detonation, but by excessive pressure caused by the higher compression ratio at boost.

If head gasket, you can be back in no time. Good luck

EdP

thus the debored 2.7t for the S4. without too much smoke, I'd huess this, as the one cylinder cycle sucks pressure from the other.... no oil to really leak.... not sure where the oil journals are between them...

Audiboy

benefit of doubt since the alloy head would be the weaker link among the two (also a thin adjacent wall leading to the the concave area of the valve chamber. I've seen these happen on cars (Honda CVCC) that overheat

Asneaky4

Thanks guys... I will find out next Wednesday and let you know.

EdP

Well, this may be the reason for the 2.7t being debored

Audiboy

what appears to be your car. He described to me a hosed PES'd 2.8 running at 40 psi in one cylinder, 90 on the other, 150 on one, 120 on the other, etc etc and they are not adjacent.

Are you ready to sport the cash on piston and crank rod replacements Good Luck