Well our Camaro (97 with LT1) has a pretty bad miss while under heavy throttle. Is is most noticeable around 3500+ rpm while under very heavy throttle. It's not backfiring and there's no Check Engine light so the OBD has not thrown a code yet. I got the water pump replaced yesterday as it was leaking real bad and my mechanic thought there was a good chance a very wet opti might cause this behaviour. I think it's better today after the new pump, but it is still missing. I am worried about losing to a Metro GEO at a light this weekend... jkjk. What do you think? Opti or plugs, or even something else?? A little advice or guidance would be appreciated... Thanks!!

 

Well if it just started doing it after the water pump change, then the Opti got wet, or you have some old plug wires that got wet. Get the car on the lift and make sure the opti is dried off and that the plug wires are totally dry and see if the problem still exists.

 

If the miss carries past 3500 to red, then I'd say it could be the coil wire or coil.

 

It sounds like the opti is going. Is it the original? Water and optis dont mix!! Try driving it aroud a few days it could(probably not) dry itself out and work fine. If not well you know! I've been there done that. on my own car. good luck
later

 

Some people have said that our cars optis are usually garunteed to go around 90k miles. But Im not sure aboout that 100%. Also dont worry about loosing to that metro, they are sooo slow that you could beat it with your car in P. lol

good luck to ya,
-John

 

I really appreciate everyone's feedback and I do feel better knowing that I can blow away a Metro in Park.... A little more background info I should have posted originally. The car is a 97 Z with an LT1 with 100k on it. The car has never run quite right since I bought it and I believe the water pump has been slowly degrading for some time. The opti obviously got soaked. My mechanic tells me it's a vented opti and he also suggested driving it for a few days to see if the opti drys out, but I don't think that's doing anything. He dried off all the leads and the opti as best as he could when he replaced the pump.

I am getting a little bummed out driving a wicked beautiful Z car that runs like a bucket of bolts when hammered on. I never thought of the coil being a potential problem here; I guess anything is possible. Because the ODB2 has not thrown a code I don't know if hooking it up to a code scanner would tell us anything? If it wouldn't then I guess it's a matter of trying to replace these parts one-by-one until the problem goes away?? We have spent a small fortune on this car since we got it and $$ is tight, as I am sure it is for everyone here. I guess I am looking for some expert advice as to where to start; which option would be the most likely to be problematic with these symptoms??

My mechanic also mentioned that because the car idles very well he is doubtful it's the opti. He said that most of the time with opti failures there are idling issues with the car and high-rpm misses are more symptomatic of plugs or other pieces....

Your advice and guidance is appreciated muchly in advance.... thank you.

 

If you are not setting any diagnostic codes I would look at the following items in this order (ease of changing):
1)coil wire
2)ignition coil
3)spark plugs
4)plug wires

My 95 LT1 had a horrible miss under load above 3000 rpm.
Turned out to be #7 plug wire which had a DISINTEGRATED wire core (inside the silicone) near (but not at) the boot.

Installed new 8.5mm MSD super conductor wires, MSD blaster coil, and AC Delco R44LTS plugs. Made a WORLD of difference !
Runs like new.

If it is the Opti, 99 out of 100 times it will set diagnostic codes.
OBD1 cannot detect any problem downstream of the Opti, thus no codes set when wires, coil or plugs are bad. I believe OBD2 is the same in this regard.

 

I voted for bad plugs... but also you need to change wires. I had the same problem you are describing and it was plugs/wires.

 

Thank you very much!! This makes a lot of sense to me and I will send this info to my mechanic and see what happens. Thanks again for your time and experience to all who replied. Plugs, wires and coils seem to be the biggest suspected culprits.

 

Well, finally got the Z into the shop and got the plugs changed. My mechanic and myself are trying to diagnose the problem so that we don't end up spending needless money chasing this miss down. We are going from most-likely problem to least-likely... and with 100k on the car the plugs seemed that they were at the top of the list.

There are no codes from OBDII and the car idles very smooth and pulls very hard right up to near redline. The plugs made a radical difference. The car is more responsive and pulls harder than it did before Hehe, not that I was trying or broke the speed limits or anything....

I did notice that there was still a miss up near redline though. It was 1000 times more subtle than it was before the plugs and for the meantime I guess I can live with it but it's one of those things that kinda bugs me.

I had the climate control set to floor/defrost. Does the air conditioner cycle on that setting? Is there any chance that it could just be the air compressor coming on/off at the same moment that the LT1 was at 5600 rpm or better?

With no code from the ODBII system we think the opti is probably OK for now, but is our next suspected item as the miss only occurs at very very high rpm, otherwise the car is smooth as butter and fast like a bumble-bee.

 

The A/C will prpbably cycle on when defrost is on, yes. But, if you had the pedal to the floor then the A/C won't cycle on at all.

Chances are it's your plug wires, if you have 100K mi and haven't changed them yet. They'll end up fouling your new plugs if you don't change them (weak spark=fouling).

 

As the plug gap increases, it will increase the load over the wires and eventually fry them. Could very well be a wires that was over stressed.

 

Unless you get the date trouble code 16 dont worry about the opti.

 

Geez, thanks guys for all the help. I guess based on what you experienced folks think it sounds like the leads are the next on the chopping block for a re-and-re. Thanks again, and I will keep you posted on how it works out. You guys rock...