Hey guys, yes I am new to this website but this misfire is kicking my but.

Basically what is happing is at idle, it gets pretty rough when its at temperature. It misses when it is cold but not as bad. It is not a constant misfire either though, which is the hard part. It will miss about every couple seconds when its cold and miss maybe every half of second when its warm. When its warm, it idles right around 500 rpm which causes the engine to almost stall, and make the lights dim. If im ideling for about 5 minutes or more, it will cause my battery to go dead so when I turn the car off and try to start it again, sometimes it wont start. Car accelerates strong off of the line also. Sometimes under a consistant acceleration, I can feel it miss once or twice. Another problem that I ran into is mainly on the highway. I will be cruising about 60 mph, and if I try to pass another car or just simply accelerate, the car will miss badly and sputter until I either let it drop a gear or until it gets up in speed. Ive replaced the air filter, air inlet elbow, spark plugs and wires. Before I just start throwing parts at it, I would like your advice as to how to diagnose what is causing it or what to replace first.

P.s, idk if I added my car info in my profile but it is a 1995 Camaro z28 5.7l LT1 all stock.

 

Sounds like the coil went south.

 

Have you checked for codes. Is the SES light on. Thats the first place I would look. If you dont have a code reader/scanner take it to AutoZone or Advanced Auto Parts and they can run a scan.

Could also be the plug wires arching off anything they are close to, easiest way to check that is at night. Pop the hood and look for a light show around the plug wires. With your stock exhaust manifolds it may be hard to see. But I have seen it before.

Plug boot may have come off the spark plug end. Also could be loose spark plugs I had that happen on my 95 formula even after I put new ones in. Did it run like this before and after you did the plugs and plug wires?

 

The auto parts stores seem to have a problem scanning the OBD-1 PCM's. Best bet is to down load the free SCAN9495 software linked in this thread:

https://www.camaroz28.com/forums/com...95-lt1-874306/

You also should check the fuel pressure at idle, with and without the vacuum line attached to the fuel pressure regulator, and out on the highway under max load/max RPM.

You need to set up a "Signature" with the basic info about your car - year, model, engine, trans and any major mods. This is set up using the "user control panel". On the red task bar at the top of every page, left click on "User CP", on the drop down, left click on "Edit Signature". Enter the info in the screen that appears, and "save". The info will be appended to all your posts, appearing below a horizontal line.

As an example, in this case knowing whether it's an automatic or manual trans would allow us to evaluate how close the 500RPM is to the programmed idle speed (550RPM in gear for the A4, 800 RPM for the M6).

 

Thanks for the quick replies! It was missing before I did plugs and wires. I did take it to AutoZone and since there was no check engine lights on, they couldn't scan it.. Checked the wires and they all seemed tight. Family friend suggested it was the cap and rotor but the highway problem was a vacuum issue. I will do a fuel pressure test when I get a day off. How should I test the cap and rotor? Seems like a pita to get to. Similar to everything in this car..but I still love it!

 

AutoZone nor any other auto store will be able to read codes even if the check engine light is on. The '95 Camaro has an OBDII style connector but is actually OBDI.

Your best bet if you plan to keep the car is to follow the link Injuneer provided and get the scanning software for your computer. You can also get a cable that will interface the OBDI/II port on your Camaro with your computer. It isn't cheap but it is a great deal/value as the software does so much more then just read codes.

There isn't a traditional cap and rotor on the '95 LT1 engine. It uses an Optispark style distributor that mounts to the front of the crankshaft. It is possible to get a new rotor and body for it but if it is bad, and it hasn't ever been replaced or it's been a long time, you're probably better off replacing the whole unit.

Another forum user on here, Shoebox, has a great site with lots of information on the LT1 engine including how to diagnose the Optispark distributor. I don't have the website link but someone should be able to provide it for you or just search around this forum and you'll find a link to it.

I have a '95 Z28 Convertible and I really love my car. As you get to know it and do things to it it's not really much worse then other cars to work on. I also work at AutoZone and that's one reason I know we can't read the codes for you. AutoZone does offer an Optispark distributor for your car. It comes with a lifetime warranty.

 

Here's the link for Shoebox's site. Spend some time there and you'll learn a lot about your car. When you're done send him some coin to support his web site.

4th Gen LT1 F-Body Tech Aids

 

Why is the Opti cap and rotor not "traditional", other than the shape? And the cap and rotor are fully replaceable, without buying a new distributor. And, the Opti is driven off the camshaft (cam sprocket 93/94, cam dowel pin 95-97).

 

Except for my misspeak regarding the crankshaft vs the camshaft i stand by my post.

Besides the shape and appearance of the optispark cover, one also doesn't have to remove the distributor to take off the cap or to remove the rotor on most cars with a cap and rotor.

I don't know why you took exception to my calling the cap and rotor non-traditional on the Optispark.
They certainly aren't like most caps anyway on most cars that have distributors with a cap and rotor.

Certainly they can be replaced on the Optispark and it's cheaper but for all the work it is to remove the Optispark he MAY want to consider replacing it IF it hasn't ever been done and or it has a lot of miles on it.

I wasn't sure how familiar the original poster was with the LT1 engine and I wanted to make sure he didn't think replacing the cap and rotor was like doing it on an older small block.

 

You may choose to pull the entire unit to replace the cap and rotor, but it isn't necessary.

Your response was written in such a way to indicate that only the rotor was replaceable, and that the other replacement was the "body". I was pointing out that you can get a cap, and replace it.

Given the number of inaccuracies in your post, seemed like a good idea to provide the OP with the correct info.

Some people want to cast the Optispark as the spawn of Satan. It is simply a distributor in an unconventional, and inconvenient location, but its still a distributor.

 

The car has 109k on it. Should I replace the distributer cap and rotor if that is indeed the problem?

 

To answer your latest question, with your car having 109K miles you'll need to weigh the labor and financial costs to decide if it is better to replace the CAP and ROTOR or to go ahead and replace the whole Optispark DISTRIBUTOR. My opinion is that if you can afford to replace the Optispark DISTRIBUTOR then do. I think you'll be happier in the end.

 

Haha in response to the apologies and corrections I have to point out an error. You cant use a jumper wire to read codes on your 95 lt1. I can on my 93 chevy truck. As Fred said many people struggle with reading the codes. If I'm not mistaken you can use some obd1 scanners using a jumper wire and I believe that info is on shoebox website but its best to just get a cable and use a laptop. As for me a lifetime warranteed opti just means a lifetime of early failure. I had over 160000 on mine with no problems and only changed due to an engine swap. Your less likely to have issues with an acdelco or delphi than the other brands.

 

I stand corrected again. That's ok, at least you did it without attitude.

Hey, that means I was right the first time!

Actually in doing some research just now I've read that some find success reading the OBDI codes with an OBDII scanner on the '95 Camaro if they enter the model year, etc of the car. I've got to try that with our scanner at work as you can optionally enter the specific model information. It seems to be a hit or miss situation.

 

Interesting that you chose to delete the multi-page, childish temper tantrum that you posted in response to my posts. Nothing like a good personal attack that you lacked the courage to leave in the thread.

Who has the attitude now?