Wacky misfire driving me nuts!

1987 Dodge Daytona Shelby Z
2.5l .020 Wiseco pistons
T2 rods, Balanced, crank scraper, rebuilt around 500 miles ago
Stock swirl head, ported 2 piece intake, ported exhaust manifold, 52mm TB, 1989 roller cam, adj. cam sprocket @ 0, billet TU fuel rail, adj. FPR, 255lph Holley fuel pump, stock fuel lines, 52pph injectors, 3 bar MAP, Magnecor wires, Champion 12YC plugs @ .035, Accel coil, stock T2 turbo 10psi, custom boost button cal, 3" turbo back mandrel bent exhaust

I think that's about it. Driving normally around town or on the highway, the car runs like a dream. The problem comes in when I mash the accelerator. at roughly 3500rpm, like clockwork, the car has a terrible misfire and a puff of smoke comes from the exhaust, and the knock sensor flashes the power loss light. I take my foot off the gas and everything comes back to normal. Below 3500, I have 0 issues, and part throttle boost is perfectly fine too. I get full boost of 10psi at the moment at roughly 2700rpm, even under part throttle. If I go part throttle to 3500, even under boost, I have no problem. The problem is only at WOT. Ive changed the fuel filter, even though the AF gauge shows rich at WOT. I took out the RN9YC plugs with no change. Plugs looked great when I pulled them, not overly rich or lean, just right. Swapped the HEP with no effect. I haven't changed the coil yet, or the wires. These were on the car when I bought it, on the old T2 2.2l. Does this sound like an ignition problem, or maybe a fuel problem, or maybe even a cam timing problem? I'm at a loss, and don't want to just swapping parts that MAY be bad. I wonder if at WOT when all that fuel is being dumped in, I don't have enough spark to keep up with it. This leads me back to the coil. Any and all suggestions are welcome! Thank you! :thumb:

Who's cal? Tried gapping the plugs down to .030"? Have you had a look at the plugs just after the misfires ... or do you run it some more then check? Driving the car around will wipe any evidence off the plugs FWIW. How's the battery voltage?

optima yellow top, battery voltage is good. I've had the misfire, then drove about a half mile to my shop and pulled the plugs, but they looked good. Haven't gapped the plugs to .030. It's a boost button cal from Shelgame.

are you hitting overboost?

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Originally Posted by audiomaninc

optima yellow top, battery voltage is good. I've had the misfire, then drove about a half mile to my shop and pulled the plugs, but they looked good.

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Of course .. like I said above.

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Originally Posted by audiomaninc

Haven't gapped the plugs to .030. It's a boost button cal from Shelgame.

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Try a smaller gap first to see if it improves. Might even need to drop to .027" or so. Easy enough to do first.

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Originally Posted by Spr-T-23

are you hitting overboost?

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Overboost is turned off in the cal. I'm supposed to be running 18psi on the low setting, and 28psi on the high setting. But until I get the new turbo, I'm running the stocker at 10psi via a manual controller.

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Originally Posted by puppet

Of course .. like I said above. Try a smaller gap first to see if it improves. Might even need to drop to .027" or so. Easy enough to do first.

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I'll try that tomorrow before watching the Giants destroy Dallas...again :lol:...and report back with the results.

Agreed, drop the plug gap.

Check your coil, remove a ground strap from a plug, ground out the base and see if it sparks, if not, coil is weak.

put a new coil in it, along with a new cap & rotor. Took the plug gap down to .030, and took it for a drive. Same problem, although in an odd turn of events, I notice that when I hammer on the accelerator, the battery voltage gauge (factory gauge), drops as the RPM increases. This happens pretty much right at 3000. I wouldn't have even noticed this, but it happened last night, and the headlights dimmed. So either the misfire is causing this, or this is causing the misfire...my thoughts at least. The alternator had been making a little noise lately, so I think I'll go pick up a new one and go from there.

make sure all the grounds are good while your at it, grounds can and will cause alot of drivability issues.

How rich are you at WOT i was blowing my spark out a 10.2-1 , I lean it out and all was fine.

talk to shelgame , i had the same problem and he fixed the cal , talk to him first

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Originally Posted by audiomaninc

I'll try that tomorrow before watching the Giants destroy Dallas...again :lol:...and report back with the results.

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:lol:hey how did that work out for you?? lol how 'bout them cowboys!!!!!!!! lol

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Originally Posted by onerippinturbo2

:lol:hey how did that work out for you?? lol how 'bout them cowboys!!!!!!!! lol

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At least they're still in first!

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Originally Posted by bakes

How rich are you at WOT i was blowing my spark out a 10.2-1 , I lean it out and all was fine.

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unfortunately I'm still running a crappy narrowband O2, so all I can say is pretty rich? :confused2: I've got the fuel pressure at 45psi with the vacuum line connected.

Get a wide band if your running that rich you causing more problems then just a missfire
i was chasing my a$$ untill i got my WB and it was rich as hell but my NB failed to show me that.

Alternator changed, problem solved! Thanks everyone!!! :-D

A wide band is still a good idea.

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Originally Posted by Jack's Dodge

A wide band is still a good idea.

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indeed it is! I'm just not spending any more coin on this car this year, it'll be going to storage for the winter. I'll be collecting parts over the winter for it and it'll be back out come spring! In the works are:

*ported head w/ +1mm valves
*TU turbo (still haven't decided between a hybrid and a ball bearing)
*wideband
*new gauges (I'd like them to match)
*new wheels and tires
*new poly bushings...all of them
*new shocks, struts, and springs
and the list goes on and on! Since I pretty much blew my load on getting the block together this year, and the terrible turbo drama I've dealt with, it'll have to sit for the winter in it's current state. I'll be driving around in my work truck til spring ('03 Neon R/T) ;)