I have a 93 z28 m6 that has 159k on it, its bone stock. I have noticed within the last few months, and the problem gets worse as time goes on. when the engine is cold, not just the water temp but literally the engine is cold it runs flawlessly but after about 30 minutes it starts stumbling and cutting out for a split second 5-6 times in a row and jerks the car pretty bad. Getting it up to the speedlimit is a chore it seems like sometimes and when Im in 6th and I go up somewhat of a hill it starts stumbling pretty bad. The problem happens in all gears at any rpm. A friend of mine says try a new set of wires but Im thinking its the distributor/ignition system on the car. 93's dont have optispark do they? isnt it a speeddensity program? Car shows NO check engine/system light. If anyone could enlighten me Id appreciate it, thanks

 

93s will hardly ever throw an SES light. Yes they are speed density, that just means they do not incorperate a MAF sensor into the ve tables. All foctory LT1's use the optispark.

With 156K miles and 15 years on the opti, your running on borrowed time. We've all seen them go farther, but It sounds like maybe an ignition problem. If you havent changed the plugs and wires, theres a good starting point. Just use oem replacements for both, or maybe step up to some NGK TR-55 plugs. Make sure you get the lifetime wires.

IT could also be a weak coilIf you know someone else with an LT1 that will let you swap them out to test, try that. Or just replace it. Ive never had one fail on me, however my friends 96 T/A had a coil go bad and it was running fine, then left him stranded. Also have a auto parts store test the ICM (ignition control module).

If none of the above mentioned works out, replace the opti. The whole unit. "ThePartsLadi" on ebay sells the cheapest ACdelco/ delphi units, which is what you want to go with. This is where I and many others have bought theres with no problems. Again, you want the acdelco or delphi unit (delphi bought out acdelco).

Before you start, you could also hook it up to an OBD 1 compatible scanner like a modis, that can tell you if its something non-igniton realated causeing this, like bad o2 sensors. o2 sensors are pretty cheap for a 93 LT1 because they use a one wire connection ($30? each).

Other things to look for:

Reach way back and push in your EGR valve and see if its moving freely. This can cause bucking and surging if its stuck.

Remove the vacume line on the fuel pressure regulater and check to see if its wet or smells of gas.

Hope this helps, lets us know how it turns out.

Josh.

 

If you don't know that your car has an opti you might have a hard time fixing this problem by yourself.

Assuming the 93 has a coolant temp sensor, that could be your problem. My car ran like crap when it warmed up and that ended up being the problem. It throws off the air/fuel mixture.

If a wire is near the manifolds, once it warms up it could cause this problem as well. It could be a lot of things.

 

Im gussing all optis are the same? This one says 92-94 LT1
http://cgi.ebay.com/ebaymotors/1993-...Q5fAccessories

$125 is that about right?

 

No, that is not an OEM opti. I wouldn't get that. Buy one from ebay seller "thepartsladi." I just got mine a few weeks ago. Price was great, and they ship it very fast. It also comes sealed in a Delphi box.

It will be more than double the price of that cheapy you just posted though.

Edit: Heres the one you want.
http://cgi.ebay.com/ebaymotors/92-93...QQcmdZViewItem

 

Thanks for the link. Il probably start with the simple things first then move on up the line until I nail the problem.