Diagnostic Help

[advizr]

I HAVE A 1994 Z28 WITH 115,000MI. 3 YEARS AGO I HAD SLUGGISH ACCELERATION BELOW 2500 RPM AND THE TACHOMETER WAS JUMPING ALL OVER. THE DEALER REPLACED THE COIL, COIL WIRE, AND OPTISPARK. OVER $1000 REPAIR. NOW I AM HAVING THE SAME PROBLEM: ONLY WHEN THE ENGINE IS WARM AND THE OUTSIDE TEMP IS WARM AND HUMID, I GET SLUGGISH (ALMOST BUCKING) ACCELERATION IN HIGHER GEARS BELOW 2500 RPM. THE TACH IS ALSO JUMPING. I REPLACED THE COIL AGAIN. NO DIFFERENCE.

ANY SUGGESTIONS? HOW ABOUT THE ICM?

CAN A DIAGNOSTIC CENTER FIND OPTISPARK PROBLEMS SO I CAN DO THE REPAIR? OR ARE OPTISPARK REPAIRS ONLY WHEN ALL OTHER DIAGNOSIS REVEALS NOTHING???

[silva96]

if she's bucking/surging it's your egr valve i had the same problem with my 96z. I tell u what do you know where the egr valve is? its a B to get to but it can be done ur gonna have to lay on ur stomach across the engine to get it. DO THIS FIRST take the vacuum hose off the egr valve, u have just disengaged the valve, take her for a ride and see how she performs if u feel no more symptoms u know its that part they are about $60.00 i drove my car for 2 weeks without that hose on until i had the time and$ to change the valve DO THE TEST FIRST i got this info from a GM mechanic when my Z was bucking.

[advizr]

I will check the EGR valve. It just seems so odd that the same symptoms are occuring as when the coil and optispark were replaced.

Also, why would the TACH be jumping all around??

[silva96]

what type of coil did u replace old one with? if ur tach is jumpin around thats gotta be coil/ignition related optispark shouldhave lasted u alot longer than that unless it was defected when was the last time u changed ur throttle position sensor? they can cause alot of problems when they blow out

[silva96]

u know what if u say your car is acting up with the changes of weather change the Intake Air Temperature Sensor (IAT) Im reading this outta my chiltons book right now they are inexpensive $22.00 or so get it from GM dealer its that sensor that goes ino the intake duct if u dont have a chiltons book pick one up it will help u familiarize urself with what all these sensors do. save yourself some $$$ do your own work and research with this book