Hi i have a 94 camaro with a lt1 6-speed . It has a missing problem and i dont know what it is . The car has a supercharger with 8psi rite now and its a 355 motor. i changed the plugs in it and went with ap104 with a .35 gap. The car will start missing around 3500 on up when cold and around 2500 on up when its warmed up. I have new plug wirers for it but would like to have more info so if any body can help please. Thanks Robert

 

It could be ignition related, AP104 is the wrong plug for your application, it could be causing your problems. But what is the rest of your equipment list?

 

The car has a full exhaust, gears , the heads have a 4 angle valve job and a port job on the heads and intake. The pistons are JE forged pistons. Other then that the car is stock. I was thinking it could be the coil, i tested the fuel pressure and its at 40 at idle and when u hit the throttle it goes to 45. I dont know what stock is but when you start car up it will load up then rev it up and its dont load up any more

 

Do you have a fuel pressure gauge in the car? under a heavy load is when you'll notice that the pressure drops if you have a delivery problem. If you have to, you can tape youre gauge to your windshield and go for a banzai run and see if you still have pressure when you need it. What you do at idle or in neutral doesn't mean its OK for a blower car. If you don't have enough fuel, it will sort of fall on its face, though, it is different than when the ignition breaks up or if your engine is detonating.

As far as my other question - do you have an intercooler or spray meth/water or a tune for the blower??? Are you taking timing out? What ignition components do you have? Do you have an ignition amplifier? How many miles on your distributor? What wires did you put on there? And like I said, your platinum plugs are a bad idea - you should stick to regular copper core resistor plugs a couple heat ranges cooler than stock for starters.

Your problem could be a lot of things, so you need to give us some information to go by. Either way, you need to redo the plugs anyway, so do that first.

Do you have any way to log data from your car?

 

Do you have the car tuned and what injectors size are you using? Has it always ran like this or is this problem new?

 

"AP104 is the wrong plug for your application" ????
That plug is at least one heat range colder than stock. Some say it's closer to 2 ranges colder. Should be fine for street work. I've used it for a couple of years with no erosion or puck loss. (The original plugs are notorious for burning off the pucks but not these)

 

You might not have problems running platinum plugs with 4.5# boost, but he is making more power and the plugs might not be right for him - it's hard to tell. It is what he changed and now it is breaking up, what do you suggest?

 

That his fuel pressure is only peaking at 45 psig sounds low (dirty filter or failing pump or FPR) ... what pump? still stock? ... a ported, full exhaust, 8 psig engine must need a 255 l/hr pump and at least 42#/hr injectors, and I wonder about whether he is still using only a stock coil and he writes it gets worse when warm which suggests a coil control module problem. (Just speculating and you reminded me I needed to update my specs, thanks)

 

Hey thanks to the guys that are writing back, I bought the car this why. The guy i got it from was not a gear head so he couldnt tell me much because it started to act up on him. The coil is stock and i dont no what the injectors are or the fuel pump. The pump is loud though so i was thinking it was bad. Thanks

 

The very first thing I would do would be to check the fuel pressure while driving where you get the miss. Then I would run the car somewhere for a free battery and alternator test. My pump is very loud compared to all my other cars and I take that as it is working good. A faint sound thats hard to hear would worry me. How many miles on the car? Your ignition could be just old if it has high miles and is original. The fuel filter is a must if you have no idea when it was done last. The four things I listed are all free to do except the fuel filter and its $15 and 15 minutes to change. and also check your air cleaner. I assume its aftermarket and maybe a K&N that can be cleaned? Take one thing at a time and maybe you fix it easy or it takes time. Always do the simple things first and avoid just throwing money at it.

 

Ya the car has 154000 on body but i think the ignition is stock . how good does your car run . Have u takin yours to the drag strip. I dont know much about chevys i just got into them. I was in to mustangs and wanted to try some thing diff.

 

What city and state are you in ? Perhaps so local members are by you and can help you out.
I'm in upstate NY.

 

I spent years trying to find a high rpm miss. I finally replaced the injectors, battery and alternator. The cars runs better than ever. My last track time was 13.25, but before many of my upgrades years ago and that was with the miss. I would hope to be mid 12's to high at the worst. I am only getting three pounds of boost, but have not really got on it (winter here) and reached high speeds since the fix. Your car has lots of potential and with the high miles I would get that original opti out and tune that thing with some 42lb injectors at worst. How long did the spark plug change take? See your mechanical ability, since these stink for that.

 

To mrmint69, I took the car down the road today to see what the fuel pressure was and it went down bad, it went down to 25 psi. O ya the plugs do stink lol, but this was my third time changing the plugs because the guy that i got it from have ngk ir55 plugs in it and it was gaped at .50 but the first time it took me around 2.5 hours but now i got it down to alittle over 1 hour now. But anyways so do u think its the fuel pump now and if i put the stock pulley back on it would a stock fuel pump and injectors be ok. But i do have three diff. pulleys for it i have the stock, the 8psi on it now and then i have a 10psi , if i would put the 10psi on it what would have to do to make the motor hold it. If i changed out the injecors with the 42s would i have to change the mass air meter too

 

I have an inline pump on mine because the stock pump can't keep up with the volume needed. What about the fuel filter? If it is real old, that alone could cause issues even if the fuel pump was fully functional and had the abiltity to keep up with demand. Someone said if you have a stock pump, that with that much boost, you will more than likely be running lean.