CEL - Randomly Runs on 3 Cylinders

[Clinical]

So I bought my 92 GST about 3 weeks ago.
114k miles, bone stock and clean car for $1200.

When I was letting it run looking around it started running on 3 cylinders. Was an older guy and you could tell the car had sat he just wanted it gone and had never had it only run on 3 cylinders - then while playing with wires and such it suddenly went back to being on 4cylinders. I test drove it, drove great.

Drove it halfway home started running on 3 cylinders. Got it home and it was running on 4 cylinders again - put new plug wires on it - last 2 weeks it has always been fine.

Then tonight it starts running on 3cylinders again.

Also I'm not sure if its related but after starting it - usually about 20-30 seconds afterwards the CEL will come on. Has a new O2 sensor.

Just wondering if this sounds like it could be a coil pack since I've had a somewhat similar issue on my old 1g and it was the coil pack. Or does this sound like it could be an injector?

Any ideas of where to start?

 

[92AWDHX40]

Whats the code ?

 

[Clinical]

Don't know need to check it but dont have a tester to check it, it's down at our shop which is about a 15-20 minute drive and probably wont be down there for about a week unless it gets so bad it isnt drivable but its never gotten any worse.

Mainly just hoping to see if anyone has had a similar issue and what their solutions could of been.

 

[92AWDHX40]

With no code hard to say, could be a coil, wires, plugs with a car you just got you really never know til you dig into it and learn more about the condition of it.

 

[Lou98GSX]

how does the car behave when you drive it does it break up misfire if it does then it could be a coil . if it just feels rough at idle then i would say injector

 

[Clinical]

it just runs on 3 cylinders, so it idles rough and drives rough , it doesnt change its always just plain running on 3 cylinders when its doing it.

 

[Lou98GSX]

while its running you can try pulling one ignition wire at a time and the cylinder that doesn't change the idle is the one that is misfiring . you should use ignition wire pliers . when you find out what cylinder it is you can shut the engine off. with the wire disconnected put a small screwdriver or if you have an extra plug put that on the wire and hold the plug up against any metal surface have a helper start the engine . if you see a spark then its firing and its not an ignition problem. also do a compression check if that is ok then i would say you have a bad injector

 

[zerq]

Zombie post!!!

Ok, my car is doing the exact same thing. Was it ever figured out?
I've swapped injectors and it went from #2 being the bad cylinder to #3. (Conpletely different set of injectors, not just moved around).

 

[triggerx]

I would recommend trying a different ECU, if you have one around. Also because these cars are so old, I know that a lot of our electrical pigtails that s
nap to the injector dont fit as snug as they should.

However I definitely suggest swapping in a ECU, they do go bad.

Ive had this exact same thing happen to me a long time ago, tried different injectors, fixed the connections, but it ended up being the ECU. Its always good to keep a spare around for troubleshooting anyhow

 

[zerq]

I put in my EPROM/v3 ECU (has a blown chip for the ISC) started up and idled fine then it dropped 2 cylinders. I went to misc and its #2 and #3. I know the coilpack works like 2 alternating sides. Is 2 and 3 controlled by the same one on the coilpack? I'm going to google it up right now but thought I'd post up anyways

I also have a spare transistor which didn't seem to fix it.