06-05-2003, 12:00 PM
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Bad Stumble
Hey All,
I have a 93 Z28 LT1. The car started acting up 2 weeks ago. A BAD ( Really BAD ) stumble and spark knock happens at low RPM happens if anything other than light peddal is used in any gear below 2500. If you baby it to that you can roll on the throttle to redline and smooth. This is consistant with one more factor it seems to be much better when motor is cold ( first mile ). Others are quick to say OPTI however would this not make it miss at ALL RPM and especially at high RPM ? Sooooo whatch think ? 
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06-05-2003, 02:26 PM
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Spark Plugs? Wires? O2 Sensors? (Right side is a bear) Sticky EGR? These are some of the answers I've recieved for a problem I'm having. Only mine is worse when the engine heats up on a hot day. I would say check those things first. Get your PCM checked for stored codes. that might reveal the problem.
Last edited by Lyle A; 06-05-2003 at 07:09 PM..
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06-05-2003, 03:10 PM
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When it is happeneing can you hear or see the spark plugs arching. Are cars run hot which deteriorates things faster (spark plug wires cracking). I had something similar happen to me in the past. Almost a 7 cylinder feeling on and off. Turned out to be a spark plug wire with a crack in it causing arching. Hey think positive a 15.2 still beats 94-98 mustangs 15.3 1/4 mi stock.
__________________
93 Z28 A4, Burgandy, T-Tops, K&N CAI, 3:73 gears. Best E.T. 13.90 @ 100 mph
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06-05-2003, 03:23 PM
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Thanks mattinator1973,
Plugs and wires down ..on to sensors I guess. I also have a 96 LT4 Vette 12.3@117 so if the 1999 to 2000 Mustang dudes wanna beat up on the poor sickly Z they can talk to its younger meaner brother :-) thanks for help. This stumble is huge like fall on its face large. now it is moved to idle as well starting to miss. hmmm any one else ?
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06-05-2003, 06:10 PM
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Hey, don't forget the coil wire
 My gosh, my car is running like a champ now. Wouldn't hurt to replace it.
__________________
The Black. 2001 SS #5697 T-tops, 6-spd, B&M ripper shifter, GMMG, SLP dual quad tips, Volant CAIS, Koni DA's & GC coilovers, Strano hollow 35mm sway, LGM-G2(SFC's w/v-braces, STB, adjustable PHR), Wilwood 6-piston red calipers front brakes w/13" 2-pc slotted rotors, RKSport(clear front & rear corners, carbon fiber grill), chrome Z06 Motorsports.
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06-05-2003, 10:24 PM
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Quote:
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06-08-2003, 08:43 AM
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Update
Ok, Wires changed plugs changed... NO CHANGE
The car has gone from a bad stumble to cant hardly get it home in 3 weeks. If it were an older car ( Pre Computer ) I would say it acts like the timing is wayyyyyy advanced ..ping knock poping out exhaust .. the whole nine yards ..so as of now the car is parked. If anyone has an idea I am way open to advise. Thanks
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06-08-2003, 10:17 AM
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Unplug the vaccum line off of the opti. It will keep it from advancing so much. You could reach 11's w/a 1.85 or so 60' from what you just posted on your times.
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06-08-2003, 10:24 AM
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Yea ..Stock tires were in heart attack mode for 1rst and second
Well Vette always ran good ... This Z is making me nuts. My only guess is that the optispark and the location of the spark plug wired was really mad at a mechanic that slept with his wife or something. Plugs and wires were an all day event. Does anyone know the best place to get a new optispark. ?
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06-08-2003, 05:34 PM
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This is about the cheapest I've found them.......If anyone has them cheaper I'd like to know...http://www.gmpartsdirect.com
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06-11-2003, 01:46 AM
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Hey LT4Z28,
Hold off on the Opti and here me out if you will. Maybe it really is the EGR valve, not the solenoid.I'm going to order one, I figured that the EGR is hooked up to the vacuum hoses, correct? So hey, I figured WTF, change it & see what happens. I just got a new Opti, and MSD coil, and still the same thing. I'll be changing the plugs & wires & EGR valve to see what happens, I've done the Opti and no luck, you've done the plugs/wires and the O2's and no luck, between you & I we've done just about everything except for the EGR. If you can get it & install it before me, please let me know & vice/versa.
__________________
The Black. 2001 SS #5697 T-tops, 6-spd, B&M ripper shifter, GMMG, SLP dual quad tips, Volant CAIS, Koni DA's & GC coilovers, Strano hollow 35mm sway, LGM-G2(SFC's w/v-braces, STB, adjustable PHR), Wilwood 6-piston red calipers front brakes w/13" 2-pc slotted rotors, RKSport(clear front & rear corners, carbon fiber grill), chrome Z06 Motorsports. Last edited by Carlos01SS; 06-11-2003 at 01:53 AM..
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