horriable missfire

[shad0w2.s_tur80]

saturday night i tried running my car up to its top speed it was all fine till i hit 4500 rpm in fifth gear. then it wouldn't rev any higher so i let off and got off the freeway. as i slowing down i could feel a slight missfire. it would kinda buck a bit when i would put my foot on the throttle and if i let off it would stall out. i pulled off the road got out my handy 30 led light(probably the best light i ever bought) to give it the road side inspection. first i checked my codes olny got 55 and everything else looked fine no oil everywhere or any dead give away sign of sever engine damage.
my first guess was the timing jumped so yesterday i went and looked at the timing it seems to be right where it should be. then i noticed that its running on only one cylinder so i looked at the plugs. to my surprise all except #1 where very lose and came right out with my finger tips. #1,#2 and number #4 where all very black and carbon covered. #3 was burnt up the electrode was completely gone ill have a pic up in bit. then i took out my wires and rotor (keep in mind these are all new wires and the rotors new as well) the ends of my wires where all burnt up and so was my rotor. after i found that i thought that was the problem so i went and took my wires and rotor back to the store and got new ones today.
i changed them all out and its still the same it will barely idle it still bucks like crazy and it pulls almost not vacuum at all like one inch or so if i don't keep my foot on the gas it dies right away. i guess its processable the timing is off as it pulls basically no vacuum. but still its not firing on #3 still no difference in how it runs when the plug wire is on or off. im gonna go play with the timing belt a littel more but im outta ideas on why its not firing on #3


btw its 1991 daytona basically stock 2.5 common block only mod is a muffler and no cat, base ignition timing was set at 12*, boost has never gone over 11psi set up all stock using a welding tip as the orifice using waste gate solenoid also

[shad0w2.s_tur80]

heres the pics of plug #3

[turbovanman²]

You leaned out or detonated, do a compression test, your going to find you have cylinder damage, IE burnt or damaged valves,

[contraption22]

Thats exactly how my brother's daytona lost a piston. Top speed runs can be deadly to a combination that is on the ragged edge.

[cordes]

Thats exactly how my brother's daytona lost a piston. Top speed runs can be deadly to a combination that is on the ragged edge.

Indeed. Exactly what the Chrysler guys were talking about when they mentioned the road course at the SDAC tech session this year.

Brief bursts didn't generate enough heat etc. for long enough to do any catastrophic damage, but the added time from the top speed run did it in.

[shad0w2.s_tur80]

ok well im done and i give up its now for sale ill have the thread up later 1000 obo

[ATaylorRacing]

Looks like a case of being to lean or not enough fuel pump.

[shad0w2.s_tur80]

their it is
http://www.turbo-mopar.com/forums/sh...438#post397438

[shad0w2.s_tur80]

ok well im back at it again i started taking the head off and when i got the valve cover off i found the rocker for the intake valve on cly #3 completely out of place who has seen this one before and can shed some light on the topic?

[turbovanman²]

ok well im back at it again i started taking the head off and when i got the valve cover off i found the rocker for the intake valve on cly #3 completely out of place who has seen this one before and can shed some light on the topic?

Yep, some piece of the spark plug or piston has jammed the valve open, causing the follower to fall off. Keep going, take the head off, its NOT going to be pretty.

[shad0w2.s_tur80]

yeah it wasn't pretty at all i just got all the melted piston off my cylinder wall im about get a different head and pop in a new piston and let her ride.

[cordes]

yeah it wasn't pretty at all i just got all the melted piston off my cylinder wall im about get a different head and pop in a new piston and let her ride.

At least you found the problem. how did the cylinder look? If it is scored up or damaged at all a new piston won't help the situation much.

[JamesL]

Doesn't look good, give us a call when your ready to rebuild.

[turbovanman²]

[shad0w2.s_tur80]

yeah yeah i know everyone wants to see pics of my melted piston ill get them up as soon as i get the "new" head back on the car.

[shad0w2.s_tur80]

Doesn't look good, give us a call when your ready to rebuild.

lol i did that last year, i bought all brand new bearings, all my gaskets and plastigauge.

[shad0w2.s_tur80]

At least you found the problem. how did the cylinder look? If it is scored up or damaged at all a new piston won't help the situation much.

well after i removed the melted piston, the cylinder wall was fine no scratches or any sign of damage i got lucky.

[Tony Hanna]

...btw its 1991 daytona basically stock 2.5 common block only mod is a muffler and no cat, base ignition timing was set at 12*, boost has never gone over 11psi set up all stock using a welding tip as the orifice using waste gate solenoid also

Something is bad wrong to melt a piston at 11- psi and 12* base timing. If #3 was the only cylinder hurt then my guess is you have a problem with the #3 injector. I believe I'd get it flowed or at the very least replace it with a known good one. Pistons don't just melt for no good reason and I'd hate to see you go through this again after you get it back together.

Tony

[moparzrule]

+1 to what tony said. I'm also going to guess a bad injector, maybe half clogged making that cylinder run lean. Judging by what happened to the plug, definitely a lean condition.

[shad0w2.s_tur80]

Something is bad wrong to melt a piston at 11- psi and 12* base timing. If #3 was the only cylinder hurt then my guess is you have a problem with the #3 injector. I believe I'd get it flowed or at the very least replace it with a known good one. Pistons don't just melt for no good reason and I'd hate to see you go through this again after you get it back together.

Tony

that's what i was thinking my self i have a few other rails with injectors so im gonna swap it out when i put my head on tomorrow. i really don't think this should have happened in the first place.