Ok here's the situation, I'm going to try to make this as short and to the point as I can....

I've got a 1994 Z28 Camaro. 88,000 miles

I did headers on it, while doing headers I also replaced the spark plugs. The old ones came out no problem and looked the way they should from a healthy engine. they burned real clean.

(headers were a gently used set of FLP longtubes w/ highflow cats. had to remove the oil cooler to make them fit right.)

The new plugs (NGK TR55) went in without gapping them because they came "specifically for LT-1 engines" from Jeggs, but i later realized that they were gapped at .059 which i now know is too large of a gap. mistake on my part.

The first run after finishing the headers and everything else that came along with it, i noticed it didnt pick up as crisp as it used to, but i figured it was all in my head.

The headers were done with the help of my mechanic, but I decided to remove the AIR smog components on my own. After twisting and yanking for about an hour, i got it all off, but in the process i f'd a few things up which i didnt notice right away. I moved the passenger side spark plug wires too close to the drive belt, that caused them to get sliced, and i also managed to loosen a hose on the water pump just enough to have coolant pissing all over my optispark. so after about a day of horrible backfiring and misfiring and running like absolute **** i finally realized what had happened. (only drove it max like 3 miles) I first replaced the sliced spark plug wires.. it helped a lot but still had issues with backfiring and missing and running crappy. So i went ahead and replaced the opti and replaced the coil for the hell of it. This helped a little, but still didnt seem right. It was lacking pick up and power, and there was a definite miss under load. The engine also shakes a lot more than it did, causing some annoying vibrations here and there. It just doesn't seem right at all

Right now I'm thinking its the plugs... they were gapped to wide to start with, and possibly got fouled out when it was back firing and missing really bad. that's what im thinking the issue is. But what other areas should I look to check??

(Things to note: It never ran like this until after my incident with slicing the wires and getting the opti wet. It Didn't throw any codes either via freescan. I also had an issue with the passenger side o2 but I think thats taken care of)

 

Did you ever re-gap the plugs (you don't mention)?

 

are you sure that all the wires are in the correct order&the plug wires have no more defects from heat
when was the last time you changed the fuel filter ?
how about the fuel pressure ?

 

I'd say that if your wires are healthy, your plugs are probably causing it. A cracked plug can cause a hard-to-find misfire, so if you dropped one or knocked or too hard with your wrench or socket during the install, you could have cracked the porcelain. If the plugs are too hard to fire for some reason, like large gap, or your wires or high voltage ignition components have weak insulation, then you need to get that fixed. you could check them at night for arcing, maybe mist some water on them and see if you can induce a misfire. Of course, it will be worse under load.

I doubt that plug is too hot for your engine, so I don't suspect that, but too hot of a plug can cause some detonation. More common if you were making a lot of power and needed a colder plug.

 

I replaced the wires and I made sure they are in the correct order. I actually replaced them twice because I had to use a ****ty advanced auto parts brand of wires at first, and it didnt make a difference between the 2 sets of new wires so I know thats no longer the issue.

I have yet to address the plugs. I've been away at college these past few months so I haven't been around my car. It's currently at my mechanic's and he's tearing into it next week and gonna fix the plugs.

I just want to make sure that I'm not missing anything here, maybe a bent valve or something random that could have happened.

 

I also would suspect the plugs as when the shop who put my headers on cracked a plug as had them change them at the same time. Since then I examine new plugs before install and gap them. Never trust a supposed pre gapped plug. I am also leary using a plug ive dropped on the concrete and if I have to use it I choose an easy one to get too so I can swap it or check it. Ive also had a plug crack tightening it down in a sloppy socket . What brand of opti did you put in? Did you locktite the rotor screws?(for security)

 

I replaced it with a chandler motor sports "top shelf" opti. I did use locktite on the rotor screws

I'm hoping it's only the plugs. I just want it running right again

 

Ive seen mixed reviews of their opti's. If after you check all your plugs and are sure no wires are crossed and everything else you worked around is connected and not damaged I would be concerned with the opti. Might inspect your vacuum lines also as you may of leaned on one and broke a seal or cracked a hardline. You might want to tell some of these guys a little more with your smog removal. Did you pull the egr and block off back of manifold. Did you remove anything from your tune or make any changes there? Personally I would suspect something related to work you did or something in the area of work performed before I would suspect a random new issue showing up. Start with your plugs and recheck wires at that time. I dont know if it would be worth checking resistance on them or not. Someone else with more experience would be better to advise that but if I knew that end of spark was working proper then I could move to the opti,coil,icm. As the other poster suggested look at it in the dark looking for arcing.

 

for the egr i did block of the manifold but now it throws a code which sucks.
for the smog, i took the pump off and basically yanked on the lines until the snapped and came out. the passaenger side was a pain to get the smog lines out. which is where i think i f'd everything up with the wires and such.

as far as vacuum ive sprayed carb cleaner all over and it didnt seem to do anything.

 

update:

got a call from my mechanic today and received some great news. He took the headers off, replaced the plugs and had them gapped properly. told me when he took them out they looked like crap which makes sense for the problems I was having. He also checked the wires and adjusted my exhaust because I was having a really bad vibration so its all good to go. he test drove it and said the power is all there and she runs great.

cant wait to go home and pick er up this weekend.

 

ok another update, this ones not so good...

I've had the car at school for close to a month now, its been running well for the most part, up until now.

Recent symptoms:

-bad mpg (close to 10 with a mix of city & highway)
-pretty sure its running rich (bad gas smell and wet exhaust)
-stumble at idle, every few seconds it will stumble and the lights seem to flicker also
-rough idle at times, shakes and stumbles worse


last few days...
-backfiring real bad (again)
-hesitating (again)
-running pretty crappy
- tonight i had the car running and opened the hood and noticed arching between my spark plug wires so thats obviously an issue im looking at...



so there's one problem that i need to address, new spark plug wires. but i have a feeling like thats not the only thing that im looking at here.

i still have the SES light coming on because of the EGR being removed, but that wouldnt be causing any issues, right?

what might i be looking at?

 

Stick to troubleshooting your ignition system and components.

 

Well I already know I probably need some new spark plug wires, but is it possible my plugs fouled out again? The symptoms are real similar to what I was experiencing before, misfiring, backfiring and hesitating, bad vibrations, etc..

I got the freescan up and I also noticed my car is throwin code 18 along with the EGR

 

I suggest you fire it up from cold and immediately use an IR thermometer to find any dead cylinders. Got to move fast. Then focus on those.

 

If you have a faulty injector (DTC 18) the dead cylinder is dumping air into the exhaust. The O2 sensor "sees" the air, reads "lean" and the PCM pours fuel into that bank of the engine, causing it to run rich. Are the plugs fouled on both banks? Is there one plug on the bank that is not fouled?