fxrob

Ok, first of all I'll list my set up.

Y8 w/SRP pistons 9 to 1 comp., Eagle rods
ARP head studs, OEM headgasket w/ copper spray
Crower turbo cam, Crower springs/retainers
Edelbrock turbo kit running 13-14psi
P28 ecu

Here is what is going on and I've had this problem before I built the bottom end also. On occasion I will get a bad misfire right around 6k rpm regardless if I'm in boost or not, just rev it up to 6k and the ignition breaks up terribly. It seems as if though I reset the ecu the problem goes away for a month or two and then comes back out of nowhere. I am almost certain it has nothing to do with my tune due to the fact that it will do it under very light throttle. I've been driving my car with the built motor for about 2 or 3 months now and had zero issues with coolant overflowing until last night when that misfire showed up again. I was in full boost and got that misfire and now I'm pushing coolant again. I also noticed a bunch of copper specs on my radiator cap now.

Before the motor was built I blew 2 headgaskets but I figured it was due to running too much timing. I did have this same misfire problem but I would pull the negative battery terminal and clean up the distributor cap and rotor and it would be fine. Now with the built motor I'm pulling out about 1 degree of timing per pound of boost and running high 11's on my wideband. I've used OEM gaskets every time and used copper spray twice. Basically my question is do you think that this bad misfire is blowing my gaskets? I have no idea what exactly is causing the misfire and it seems quite odd that resetting the ecu fixes it and it runs perfectly for a month or two after that.

The ignition is all stock and I'm running Denso Iridium K20 plugs. Anyone have any ideas? Oh and the block was decked and head resurfaced when I built the motor.

D-booster

May not help but.....maybe your pulling too much timing to soon. I run Uberdata and I have my timing pulled .25 to 1.8 degree's depending on amount of boost. Also...whats your total timing? I'm running 20 @ 11 psi no problems here.

D-booster

Also a miss fire can cause a blown head gasket if its do to High EGT's. Not enough fuel or to much fuel perhaps. Although this still does not explain why reseting the ECU helps.

fxrob

Well I'm running the Link engine management system so it is only pulling timing out under boost. It uses the stock ecu for non boost driving so the tune/timing can't be what is causing the misfire since it happens even when in vacuum.

My EGT's are fine, they've never gotten over 1200 degrees fahrenheit.

I'm thinking it has to be some type of electrical gremlin, it will misfire a the same exact rpm regardless of throttle position/load. I've made sure the ground for the Link piggyback was good, even changed the ground location and it made no difference. One thing I was considering is that the ignition is wired into the Link box so it can retard timing under boost, maybe somehow the Link box is going haywire and screwing up the ignition signal Keep the ideas coming!

maddog20

Oh man this is a tuffy! It is so intermittent. So your running a obd1 ecu with the Edelbrock Link piggy back that is for obd2. That maybe your problem?

fxrob

The Link has been reprogrammed (I have the Link handheld tuning module) so I don't think that is the problem. The more I think about I'm starting to believe that the Link box itself is the problem. I just pulled my negative battery cable and it fixed the misfire problem. Next time it happens I'm just going to pull power to the Link box and see if that fixes it, if so then I know it is the Link box and not something else.

So I guess my main question now is about my headgasket issues. I know that running a P28 ecu on an OBD2 car seems to advance the timing a bit since my car detonated when I put the P28 in. For all you tuners out there, do you think that pulling 1 degree per pound of boost is enough for 13-14psi w/ a P28? Like I said everything seemed fine until last night when the misfire came about and now I'm pushing coolant again. I'm almost thinking I should just put the P2P ecu back in

SOHCmaster

Plugs fouling.. I foul alot on my SOHC, gotta go tighter gap try 28-30..
Does it pop like a popcorn bag poppin out the exhaust under load, if so its time for plug change, thats what I always do like every 2-3 weeks..

warrick

you change your spark plugs every 2-3 weeks? jesus christ.

fxrob

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by PK SPEED &raquo;</TD></TR><TR><TD CLASS="quote"> Plugs fouling.. I foul alot on my SOHC, gotta go tighter gap try 28-30..
Does it pop like a popcorn bag poppin out the exhaust under load, if so its time for plug change, thats what I always do like every 2-3 weeks..</TD></TR></TABLE>

Did you not read what I just posted? The misfire is fixed now that I disconnected the battery for a few minutes. How would that fix fouled spark plugs (that I don't have anyway)

maddog20

you where saying this happened prior to the engine being built. Did the backfire happen after the p28 install or Link install?