bufmatmuslepants

iTrader: (3)

I searched this forum and others for this problem and found lots of threads about it but none ever have the original poster come on and say "I did _____ and it fixed it" so here we go. This is going to be 1 of 3 threads with each of the 3 problems I have now. LONG THREAD with all details want this fixed fast.

The Car:
94 Z28 M6 137k on body. Stuff put on 3 years and 37K ago: MSD vented style opti with all vents ran properly and loctite on the screws inside it, Taylor 8mm wires, waterpump. Stuff put on 2 years and 20k ago: K&N intake, ported MAF body, uncoated 2 1/2 year old LTs which are starting to rust, ORY, underdrive pulley without the complementing alternator pulley so guages dim and blinker slows down at low rpms, Trifecta mail order tune. Stuff put on 1 year and 7k ago: roughly 100k mile longblock, GM replacement clutch, eurathane motor mounts, all new vaccuum lines, swapped intake manifold valve covers and oil pan from old engine onto this "new to me engine" with new gaskets and black RTV torqued to proper specs on install but never retorqued since, Bosch 02 sensors with homemade extensions soldered and shrink wrapped individually then shrinkwrapped all together, NGK TR55 plugs gapped to 0.040. Fuel filter has never been changed since Ive had the car for 37k miles.
All work done by me with car on cinderblocks and basic hand tools, I am not a mechanic and most of this stuff was first time experiences for me, but graduated mechanical engineering from WVU so I know concepts.

The problems:
Car progressively started missing this spring, then was running on 7 cylinders, but had to drive it 500 miles home from school so did it on 7 cylinders. Parked it for 1 month in grass in parents yard in CT and it didnt move. Came back and when car was cold, started it for 5 seconds then shut it off and felt each primary and found one that did not burn me, therefore no spark in #1 cylinder, looked underneith and serpentine belt had cut plug wire in half. Replaced all wires with Taylor 8.2mm wires except #7 because that one sucks *** and wire looked fine. Started it up for 5 seconds, shut it off, all primarys burned me, car was now firing on all cylinders, idle improved, still doesnt feel perfect when driving it but didnt have time to really get it nice and hot before leaving again. Parked for another month and a half in muddy grass.
This past weekend went home with a friend to have him drive the camaro down to new job in VA. Car started right up, idled decent, primarys all burned me, so we took off in the pouring rain. We stop after 10 minutes to get gas and he says its missing a little and backfirng a little with not all the power it should have. I say **** it lets go. Progressively gets worse as the drive goes on, but I think its just that something doesnt like moisture cuz it has kinda always done this. Stops raining after about 3 hours and everything dries up, but Joe says its still getting worse, backfiring alot, surging, missing, hesitating, no matter what rpm, light throttle WOT whatever. In traffic I can hear him blipping the throttle to keep the oil pressure up and every time he lets off it backfires through the exhaust. He says he cant pull at all in 6th without vibrating like crazy. At 228 miles he calls says hes about out of gas, normally I get about 380 miles to a tank. Driving behind him I can smell fuel so I know its running pig rich but its not smoking other than from the oil dripping on the Y pipe and collectors Im pretty sure (leaks like a sif). I drove the car yesterday with hopes that it would drive nice while it was cold in open loop but it still doesnt have all power and is missing, but when its warm it does run a little worse than cold but cold is still shitty.

I just bought new NGK TR55 plugs and a new AC delco ICM and will try them tonight as well as running a ground strap from the block to the frame. Other options Im thinking are to try a AC delco coil and then AC delco O2 sensors. I want to find which thing fixes it so Ill change something and if it doesnt work return it and try something else. The car is parked the street in a pretty nice neighborhood right now as I am renting someones basement which limits the work I can do. I am in Alexandria near Kingstown if anyone is in the area who wants to help. If anyone has had these problems please tell me what fixed it. Thanks and sorry for the long thread.

bufmatmuslepants

iTrader: (3)

It was a spark plug wire touching a primary .

gearhead3340

i keep hearing spark plug wire touching a primary, touching a primary? wat kinda primary. because im having the same issues and havent found a solution yet, any idea wat color the spark should be when u put an inline tester in between the spark plug and wire mine was a bright orange. is this normal?, most other vehicles ive checked this on it was more of a bright blue,

94_LT1_TransAm

He means that the Spark Plug wire was touching one of the four header pipes before it reaches the collector.

gearhead3340

how about injectors if i unplug my # 5 or 7 injector it does nothing which would indicate to me thats where the problem is. anyone else no of any known harness issues with issues with the injecters. it keeps throwing a 18 code.

atlantadan

Code 18 is "injector circuit" so maybe test them with a noid light and see if they're pulsing.

bufmatmuslepants

iTrader: (3)

This is a 7 year old thread and brings back fun memories, but there's some easy troubleshooting you can start with on yours. If you have long tubes, start it up cold, let it run for 30 seconds then shut it off and go grab your header primaries. If any of them don't burn your hand, that cylinder isn't firing. If it's not firing, it's missing at least 1 of the 3 things it needs to fire: spark, fuel and compression. Start with spark, so pull out the spark plug on the dead cylinder and plug it into the plug wire in your hand. Hold the tip of the plug to something metal on the car, like the block or chassis, of motor mount, by holding the PLUG WIRE BOOT in your fingers,or if you are scared get pliers with rubber handles to hold it, and then have someone start the car in the dark (or dimly lit area) and see if you can see the spark on the plug as the tip is grounded to the block/frame whatever. Or if you really don't want to hold it in your hand go get a spark tester (dummy plug) from advance auto for $7 and clip it onto the frame and watch for spark. If you get spark move on to fuel. Being number 5 and 7 are dead I always suspect the plug wires, they are next to each other and horrible to access, so I would guess they are damaged by either touching the exhaust or cut or something.

Pull the fuel rail and swap the dead cylinder injector with an injector from a good cylinder and them fire it again and see if it burns you. If the dead cylinder followed the injector, it's a bad injector. If not, it's upstream in either the wiring or you have no compression and should do a compression check. The other option is you have 5 and 7 plug wires swapped, or 5 and 7 injector plugs swapped. Did this happen out of the blue or did you work on it and then this started happening?

gearhead3340

i bought the car like this i figured it out some due to lack of time, but my injectors arnt getting there ground pulse. any known issues with the harness on these cars, im getting ready to swap whole fuel rail and injectors and see if that works, i already swaped ecm with a known good one and still same issue, if it stays the same after i swap fuel rail and injectors, then next im gonna cut rewire the whole injector circuit and see how that goes. i do appreciate yalls imput btw

gearhead3340

i figured it out, thanks guys for the advice shes running amazing now,it was 2 injectors shorting causing the ground to be intermittent, changed the whole fuel rail because i had a spare, and hot damn. shes running again.