Drivability problem and diagnosis
 

I think I may have a bad OPTI but I just want to try and rule everything else out.
Car:
95 lt1 firebird, Vortech supercharger(@ 50,000), long tube headers(@65000), Ignition, computer and all sensors are stock. I had a small waterpump leak last year after I took it out of storage but a bit of stop leak and driving has resolved that problem. Car now has 81,000 miles.

Symptom:
Some missing and stumbling and seems to be running fat. At first it seemed to be only when warm, now it appears to be more frequent.

What I have done to date:
Had it scanned, only seemed to have a couple o2 out of range. Seems the wire to one of the o2's was shorting on header. FIXED.
Fuel pressure is good, vacumn is good
Checked for any air leaks between MAF and supercharger and supercharge and TB:NONE
Wires seem to be good, plugs are good.
Unpluged temp sensor still ran bad.

Any help would be greatly appreciated.

Re: Drivability problem and diagnosis
 

Well, since you mentioned it does it more when it's warm, it sounds like a closed loop problem. Try unhooking both O2 sensors and driving it. That will put the car in "open loop". Let us know how it runs after you do this. Then, we can go from there.

Re: Drivability problem and diagnosis
 

I thought unplugging the temp sensor(water pump) would put it in open loop? If it did not, I will definitly try the o2's. Thanks, your quick

Re: Drivability problem and diagnosis
 

I've never tried unhooking the temp sensor. I always do the O2's, that way I know that the computer can't learn from them and the car will read from the open loop tables. It worked for me last weekend. The car was running horrible (new setup and mail order tune), so I unhooked the O2's and it ran much better, not perfect, just much better, and I got 5 more mpg.

Re: Drivability problem and diagnosis
 

How old is your opti? If its over 100k then I'd replace it along with the water pump. I went with an electric WP which is a little more difficult to install but makes the car run cooler.

Are you running the crane ignition box? If so, make sure it is grounded really well. A bad ground can cause misfires just like an opti problem.

Re: Drivability problem and diagnosis
 

OPTI has 81,000. I am not using the Crane ignition, it failed on me a couple years ago so I am running a stock ingnition.. thanks

Re: Drivability problem and diagnosis
 

Stock ignition? Wow. The first thing I would do is upgrade that baby. Get a LTCC or Delteq. I went with a Delteq since it was a more complete kit and much easier to install. It made a HUGE difference on my Vortech supercharged car. The thing still fires with a ton of oil in the cylinders. LOL!

Re: Drivability problem and diagnosis
 

Okay after much tinkering I think I have it. It appears to be the o2's I unplugged them and it seems to run fine. I will be repalacing them this weekend. The service engine light did not come on with the o2's unpugged, is that right? I will leave final post after installation.
Many thanks guys

Re: Drivability problem and diagnosis
 

It won't throw a code with BOTH O2s unhooked. Glad it ran good w/out the O2's hooked up. That's a much easier fix. Post back and let us know if it fixes it or not.

Re: Drivability problem and diagnosis
 

It was the o2's. I replaced them with original gm sensors and I have driven a couple hundred miles. Running great. thanks again

Re: Drivability problem and diagnosis
 

Congrats.