Hi, My 96 lt1 hot cam car is running like crap. It has a lot of lope at idle and runs rough with the motor shaking. Then at wot the car will stutter bad. I do have an O2 sensor in the passenger side header that I think is damaged; from me jacking the motor up. But I thought the O2'S don't work at WOT. I did just change my opti. Before I did my opti I was having a ping at the top end but no miss, now with the new opti I have a miss but no ping. I also changed the wires and plugs when I noticed the miss but no luck. I am thinking it's the opti or that O2 that I think may be damaged; but I am leaning more towards the opti. What else could cause this. The Icm and coil were also tested.

 

It's possible the opti is not on right. Happend during my cam install and it would barely run.

 

I think the opti is on correct. It runs strong but it has a shaking idle and a high rpm miss. I have installed the opti incorrectly and the car really runs like crap; like you said it barely runs. The car has good power and seems to run good down the highway at 70mph. But It has a miss when I am in overdrive at 45mph that I can barely notice. At idle it is rough shaking and sometimes bucking; then at WOT it seems to run strong until it gets high in the rpm range then it stutters. The opti is a Autozone opti.

 

Have you at least put a mail order tune in it after the cam swap?

 

it ran fine until the opti swap? did you use your obd2 pcm and have egr and whatever else tuned out of it? i have the same setup as you (lt4kit,hotcam,headers)except mine is a manual trans. i went with an obd1 conversion and if i plug my untuned obd2 pcm in it runs terrible. either pcm you have should be scanned for trouble codes. obd2 is fairly intolerant of misfire and should flag you a code or 8. if you do have obd2 onboard the better scan tools will allow you to see exactly what cylinders the misfire is happening.

 

The car has a MADZ28 tune. It is a 1996 obd2 car. I have a scanner but it shows no miss fires. I think it will no longer read the miss fire because I installed a double chain and had ION tune out the crank shaft position sensor; I think that is the sensor that detects miss fires. There are no codes showing as of now.

 

I think I am going to trade my opti in at auto zone for another one. If that dose not work I am going to have a retune, have the crank shaft positioning sensor activated and throw in a stock chain set. Then I should be able to see what cylinders are miss firing with my scanner.

 

What kind of vacuum are you pulling at idle? It should be around 15-16 inches. If you are not pulling that much then you must have bad rocker adjustment or some kind of intake leak.

Here is a video of my CC503 LT1 pulling a vacuum reading(last half of vid).
http://www.ace1252.com/images/CC503_...ant_tester.WMV

I'm OBD II also....my misfire code is disabled too.

 

I am going to try that tomorrow. Where should hook the vacuum gauge up at; can I unhook the fuel pressure regulator line and hook the gauge up there? Thanks

 

Ok I tested the vacuum and its between 14-15 inches. I pulled the opti out and found that my rotor screws were loose; one was totally out, and the other was really loose. I think that was my miss. Should I replace the cap and rotor or just loctite the rotor screws back in. The cap and rotor dose not seem to be damaged at all.

 

Cool deal. I hope that is the problem.

For vacuum testing, I pull the vacuum source off the fuel pressure regulator and use that tube(sorry late on the reply).

I don't have any experience messing with anything but a new opti. However, I think others have used loctite with good results.

 

I got every thing back together and thank god the car finally runs good except for a slight rough Idle. But I think the idle is normal for a hot cam in an auto car with 3:42 gears and stock stall. Thanks ACE I was thinking valve adjustment or opti for the high rpm miss and once I tested the vacuum I knew it had to be the darn opti.