mjones60

I found out that my car had two spark plug wires that were burnt by the passenger side header. I changed the wires and the plugs and its still holding back power. It runs good at idle but when i push the gas it seems as if it still has a misfire. There are no check engine lights present. I hope it isnt the optispark distributor that i have to change. I also need to pull the wire to see if the wires are sparking the plug because the connector boot on the optispark is hard to connect on that passenger side. I also have the Bosch Platinum fusion Spark plugs in there. People say those plugs causes misfires sometime.

parkers Z28

After you check the plug wires that you haven't looked at I would scan it to see if you have any codes some of the codes won't turn the engine light on ??? I think ????
have you checked the fuel pressure ??

white97T/A

I have heard people complain about Bosch plugs but I don't have any personal experience with them to sway me one way or another. Personally I run Delco plugs, and I have used NGK plugs before too.

On the symptoms that you are describing, once upon a time I had virtually the same symptoms that you are describing. Lack of power, hesitation, runs fine at idle and no check engine lights. For me the symptoms lasted about 3 months and I kept checking and checking to no avail... Finally and suddenly while driving accelerating from a stop light the car died and then would not restart. After towing it home and troubleshooting I discovered the opti was bad. After replacing the opti I have never experienced that issue again.

mjones60

I replaced all the plugs with Double Platinum Plugs and its still the same. It acts like it wants to go but it surges and backfires. It idles great and the plugs are getting fire. I'm thinking the optispark messed up when the plug wire hit the header exhaust...Its like the car has a shortage...I don't know how hard it wouldbe or how long it will take to change the opti but that is my next thing because its sitting in the garage and I'm itching to get back in my Z...I have no vacuum leaks..

white97T/A

If you have access to a scan tool you may be able to see that the timing is being retarded causing the lack in performance. I don't think that burning a plug wire would hurt the opti, probably just a coincidence. To replace the opti you have to remove the waterpump and that harmonic damper/crankshaft pulley, and then you will be able to take the opti off. I would allow the better part of a day if it is your first time.

mjones60

I have came down to thinking that it has to be the O2 sensor from the passenger side because thats the side that had 2 dead cylinders and it may have got messed up in the nonfiring process. Its the only thing I havent considered and that may be my problem. because everything was already working fine. Every once in a while it starts running normal then it boggs. I know that I dont have a shortage in it. Wish me luck because this has been a headache because I have replaced everything and Im tired of spending money on this car.

mjones60

Problem Solved! I think it was my O2 sensors. I changed them out and reset the PCM and ECU and it ran like a scalded donkey!!!!!!!! Too bad i spent all the extra money on plugs, wires, and time...I also had to put a new aluminum throttle elbow on the car because the oem one was torn after pulling it off so much. I also think my ecu had a little shortage in it because when i fiddled with it, it seems like something was loose. I pushed the wires in and its running good now. No misfires. Glad i didnt change the opti because that is a pain and expensive. Thank God for Forums and Google.

Injuneer

The ECU and the PCM are the same thing. What part are you calling the ECU? By "shortage" do you mean an electrical "short"?

Zfbod94

Good to hear you fixed it with the O2 sensors. I just had this exact same problem with my 94 z28, but I already had new O2's in it. Turns out the coil was shot. I tested it according to Shoeboxes test procedure and one of the terminals was at 17 ohms resistance where all the others were around 5.8 ohms (MSD Blaster 2). And it runs great now.

mjones60

it wasnt a shortage in the ECU the connector on it seemed to be a lil loose so i jammed it back in. There is a fuse on the inside panel that says ECU and a fuse under the hood that says PCM so i didnt know if it was different so i pulled both. I just changed the spark plugs to Autolite Double Platinums. Didnt think the O2 sensors would cause me so much pain in the pocket because i went thru everything.

Injuneer

The fuse in the panel at the end of the dash is the switched power to the PCM, and labeled "PCM IGN". The one in the panel under the hood is the unswitched (memory) power to the PCM and is labeled "PCM". It's the one in the box under the hood that you pull for 30 seconds to clear the PCM volatile memory. I've never seen a fuse labeled "ECU" on a 95.

This is the PCM (courtesy of Shoebox).....



There are 4 large connectors on the back. Was one of them loose?

mjones60

Yes I think one of them was loose...When I thought I was resetting the Pcm or Ecu I was pulling the one on the side of the dash and it didn't do too much.


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