The car has brand new 8.5 msd wires,New NGK TR-55's and new coil. The car runs great until the engine temp. gets @ 150 degrees and up. At Idel and W.O.T., it seems fine. Starts fine also. But, under light (normal) acceleration and on up through the rpm range, it has a steady miss and the exhaust cracks,pops and sometimes backfires (pops and cracks like a cold flowmaster) The longer I drive it, the worse it seems to get. Could this be the opti? If so, is it the opti-sensor or just the cap and rotor or both? Were is the best place to buy these? B.T.W., the 97 Z28 has L.E.stage 2 heads and cam, longtubes, 58 mm throttle body etc> and 61,000 miles. Car hardly gets driven. Thanks for any suggestions,Troy.

 

did u check all the wires/plugs to make sure they were on all the way and not loose? also... is the gapping on the plugs correct?

 

Probably an opti.. My car kept fouling plugs due to running way rich then the opti went out during monsoons with similar symptoms to yours.. You should just get an LTCC setup and call it good.. It was very easy to install and even helped with gas mileage.. Best of all you dont have to touch the opti since the LTCC just uses the hi and low res signals from the optical sensor.. PM me if you want some pics of my install..

 

what is a LTCC? Is that like a Delteq? Plugs are gapped at 50-55 and the wires are all on tight with no burns. THey clear the headers by 3-5 inches. Thanks for any more suggestions. Troy.

 

http://www.geocities.com/reilym/LTCC/
http://delteq.com/products_opti.htm

 

I had the same problem and turned out i had one burned plug wire. put it on and it ran better for a little while. the real culprit was a bad 02 sensor that wasnt failing to the point of throwing a code. so if the plug wires arent burnt that would be the next thing to do.

 

My car has been concerted to a OBD1 (PCMFORLESS Program) Will my car still through the codes?

 

yeah but not as many as it has when it was an obd2. ob1 doesnt have as many diagnostic features so it would only throw a code if an 02 completly stopped working i believe. i would change them after checking the plug wires.

 

OK, I'll do the 02's first. Hope it helps. Is there any way to check these, like try running the car with them unplugged and see if it is any worse. Thanks for any more info.

 

well i know with ob2 if you unplug one itll put the computer in continuous open loop mode. i did it with mine and the car ran great. so try unplugging one and reset the computer by unplugging the ecm fuse for about a minute then start it up and run it for about 15minutes(takes the computer 10mins or so to switch to closed loop. if you have a scanner that would be ideal to check for sure but if not then just wait and see if the problem occurs again. if it doesnt then its the 02's

 

any more suggestions guys?

 

in all likelihood, its a spark plug not sparking causing unburned fuel to pop in the hot exhaust instead of in the cylinder.

So anything that can cause a spark plug to not fire. Follow the circuit, and start by looking that the cheapest/easiest things to replace.

 

I would guess there are some spark plug wires crossed somewhere...

 

my car is doing the same thing. pretty much. i just put another opti on last weekend and after the temp got up some it started back doing the same thing. i have the delteq setup so i dont know what could be causing my problem. sometimes it will pop back thru the cold air ind. and if im riding on the highway it will stumble bad in o.d. if i pat the gas or pull it down to 3rd it will clear up some. could this be a fuel problem? also the car smells rich at idle.

 

I had a similar problem once before... One morning it just started missing and popping thorough the muffler. Lost power and Shaking like a ****. I had my old opty with 148k miles on it. (original opty) So I figure the time is up for a new one.

To make a long story short... I pulled #1 spark plug out before I paid for a new opty...... guess what? I had developed a hairline fracture on the On the porcelain that covers the center electrode and it mustve been sparking around it cause it was carbon fouled up everywhere else but along the hairline fracture.

I replaced it with an old bosh platinum spark plug that I never threw away and BINGO... problem fixed.


I had two similar problems now with the insulator cracking on NGK plugs now. I am still using them as I think those were isolated problems.


Marvin