Sorry for the long post but stick with me. Well i finally did a full tuneup of my recently acquired GTA. I've put all platinum plugs, 8.5 superconductor MSD wires, an accel cap/rotor, accel supercoil, an accel ignition module, oil change, pcv valves. The only ignition component i didn't replace was the pick-up coil. Well it still has a few problems: the idle has improved but it still idles somewhat low/rough when in gear. Its not real rough but the car vibrates a little and almost feels like its missing a little (i know autos idle a little lower maybe thats the way they are). now it takes significantly more cranking to start (before it fired right up). Not only that, when the RPMS get to about 3500-4000 the tach blanks out. It didn't do that before with the stock coil. The only thing i didn't replace was the fuel filter (my jack's broken), which might explain the still rough idle but not the start-up problem.

 

Is there any chance you moved the distributor when replacing your ignition components? How is your timing...stock 6 degees? Are the new plugs gapped at 35?After checking to make sure the plugs are gapped correctly and the distributor and timing are right...here are a few things I would check which have worked for me in the past...

While applying the gas at idle and holding the rpms lightly and steady anywhere between 1500-2500,if your rpms miss and don't stay steady,try the fuel filter. Our cars pump alot of fuel at a high psi through the fuel filter,that's a good place to start for cheap.
Next step may be the idle screw adjustment if you feel your IAC and TPS sensors are within normal range. Your new ignition components can draw more power than your old worn units. My car never idled properly and came to find it was just an improperly set idle screw. If your distributor hasn't been bumped and the timing is correct,here is the proper way to adjust the idle screw...
(1)Bring the car to normal operating temperature,turn the car off.
(2)Insert a jumper between the a and b terminals and turn the key without starting the car. Wait 30 seconds and with the jumper still in,unplug the IAC connector.
(3)Take the jumper out and start the car. With someone in the car,put the car in drive and hold the brake.
(4)Adjust the idle screw until you achieve 450 in drive. Turn the car off,rehook the IAC connector,and disconnect the battery to clear the codes and reset the ecm.
(5)Hop in and drive the car for a good 20 minutes under normal throttle conditions,the ecm will relearn and reset the idle to spec 750 in park and 600 in drive at idle.
After going through the normal tune-up(which you have done) and the above idle screw adjustment,if the idle is still off try the CTS. The ecm relies on the CTS heavily at idle,the CTS has made a huge improvement twice for my idle.
Lastly,as for the shaking car at idle...my car shakes as well at idle yet my idle is perfect. I wouldn't assume it's your idle which causes the shake until you cure the idle first. My shake has nothing to do with the idle,once it was loose converter bolts which I retorqued and now it's the flexplate. Check into these if your shake persists after you fix the idle,the flexplate and converter bolts backing out are common problems on thirdgens.


Hope this helps a bit,has worked for me and hopefully will for you.
Niko.

 

Thanks for responding. Anyway i made sure to gap the plugs .035 and i didn't remove the distributor when i changed the module and cap/rotor. I'll borrow a timing light from my friend this weekend and check the timing anyway. I'll check the tps and iac as well.....What still gets me is the tach blanking out at 4 grand.....

 

Red,

Niko covered the throttle minimum air position adjustment procedure pretty well, adn that would be a good item to check. While you're doing that, it might be a good idea to clean the throttle body and IAC air passages. A dirty IAC cannot control the idle air very consistently.

If all that doesn't solve the idle problem, change back to your stock coil and bypass the MSD CD box for mow, just for troubleshooting purposes. The tachometer "blanking out" is indicative of a coil primary problem, or wiring at the coil promary. Once you're back to basically stock configuration with clean plugs and new wires, you can resolve the issues.

Make sure the fuel pressure is correct. A fuel pressure gauge is about $30.00, and can be a valuable diagnostic tool. While you're at the parts store, you might want to grab a new fuel filter as well. If you haven't changed it, it is probably overdue.

I chased a rough idle problem for a year until I finally got over my denial and proved to myself that the "professionally cleaned" injectors were not flowing correctly. I removed the injectors and sent them off to Cruzin' Performance for analysis and cleaning. As expected, the injectors were WAY off in flow (one was 38% low) and spray patterns were terrible. The cleaned injectors came back to me in a few days and for less than a hundred bucks total the car ran better than new. The car only had 22,000 miles on it at the time, and injectors were supposedly "cleaned" at the dealer under the pressure feed system the previous year (and for well over the hundres bucks).

While that may not be your problem, if you exhaust all other possibilities, you might want to consider diagnosing the injectors. You can perform a power balance test of sorts to get an indication. It worked well for me.