Firehawk197

My car was running fine then at an idle it started missing hard so I limped it home and started the diagnostics. After checking I have found that cylinders 5,6,7,8 all are no longer firing, they have spark but not 100% on injectors but has anyone heard of half of the injectors just quit working during normal operations? Car is a 94 firehawk with 388, 36lb bosch injectors, tuned pcm, and stock ignition. Any help is greatly appreciated.

Firehawk197

Update: Injectors all have pulse checking valve train next.

SS RRR

iTrader: (2)

I'm going to guess a loose rotor on the opti.

Firehawk197

I have decent/consistent spark all the way through the plugs which makes me think i would get a backfire of some sort. But the cylinders that aren't firing plugs are all black like they are fouled so the only thing I can think is compression but it is odd that it happened on 5678

Firehawk197

So compression check says cylinders are ok. Still 5678 aren't burning right or misfiring compared to 1234 and while it is running the smell of fuel is strong as if it is not burning it so can someone give me a reason to think this is the optispark? I've changed it maybe 40-50k miles ago. Again any help is appreciated and sorry to SS RRR for not even thinking the opti.

JOHNNYMO

iTrader: (1)

What brand opti? I have an MSD that only had a few thousand miles on it and its optical sensor went out. The tech at MSD told me there was a bad run of them. They will rebuild it for about 120 bux plus shipping

Firehawk197

It is a Delphi brand but could the opti make 5678 not fire and 1234 fire? 5678 has spark but if its not at the right time its not really any good

96z28_lt1

iTrader: (3)

it depends, if there is something wrong with the cap or rotor or the sensor wheel. Have you replaced your fouled plugs and seen if it was better and that it wasn't just fouled plugs giving weak spark to those cylinders? Also are your injectors leaking at all, although it would be weird for all the rear injectors to go at once. However fouled plugs is a sign of to much fuel and not enough spark. Also go over your wires well, if you have longtubes the back wires are usually the easier ones to get burnt.

Firehawk197

No burnt wires fouled plugs have been replaced and injectors not leaking. I'm not sure what to think of this one.

Firehawk197

Back from the dead. Since my last post I have replaced the optispark thinking it was the culprit as it has been every other time. Turn out it's not that or the coil, and after further investigation it would appear the back four cylinders aren't completely not firing they are burning a little bit or firing at the wrong time. It is almost like the front four (1234) are burning way hotter than 5678, almost a lean/rich or maybe some kind of timing issue thats not opti related. Any thoughts comments? Am I looking in the right place? Also the pcm grounds are good checked those too.

moehorsepower

iTrader: (3)

On a slight chance it could be the PCM, Do you have a buddy with a 94 or 95 that you can swap PCM's, I know you have 36 lb injectors, but just for start up to see if all cylinders would fire, We had a Impy, with a misfire, changed out plugs, wires, ICM, Coil, Opti, Injectors, and still the miss, change out the PCM, Gone..

BellTech

Y'all were talking about the distributor, what brand do y'all actually recommend? I saw the comments between MSB (with the production issue) and Delphi but I found one for $149.00 at my local autoparts store made by Richporter... Could the opti-spark really be the only culprit behind firehawk's and my similar issues??


Sorry to hear about your issue firehawk, just throwing this into this conversation that I'm having a similar issue with my 97, except mine won't even stay running. crank and it fires but if i don't feather the gas it dies, if i feather it right then it will stay running between 100 and 500 rpms sometimes going as high as 1,100rpms followed by a very loud backfire then dies.

I'm gonna keep a close eye on your post here, the advice you're getting here is all things i need to do tonight.

moehorsepower

iTrader: (3)

ALL Optis are hit and miss, I purchase a GM Delco from the dealer, would not even start the car. Someone I know has a autozone $150 opti and going strong.
What ever one you buy, make sure to put a little locktite on the rotor screws and on the vented ones, make sure you connect those lines.

JOHNNYMO

iTrader: (1)

Id say your issue is the optispark. mine was doing the exact thing as yours. The MSD opti is a nice piece and they rebuild them for about 120 bux if they go bad. Trick is buying one cheap from someone that has a bad one, then send it in.

Firehawk197

I will check around with a few parts guys for a pcm. I believe I have a good opti seeing that having two do the exact same thing no one has heard of would be kinda rare. Would or could an icm do this? BellTech's problem that sounds like what my first opti did till it just quit running altogether.

Firehawk197

Solved this problem finally! Turned out to be a cracked/broken valve spring #6 exhaust. I must have over looked it.