Bocefus

I am having an issue with my newly purchased 93 LT1 car right now. It runs and idles fine when its warming up, in open loop, but once it warms up, it runs very roughly. It will cut out when you gas it a little to accellerate while the car is in gear and driving. Pressing down the accellerator more than 1/4 throttle will cause the car to cut out, and if you continue press down the gas peddle, it will just ping under the hood. It won't accellerate at all unless you very gradually work it up to speed.

I just finished spending 7 hours changing the spark plugs and wires, and was really dissapointed to see no improvement. The car has 52,000 miles, and it looks like all the tune-up parts are original. It isn't showing any codes at all when I checked.

Does anyone have any idea of what my next part change should be? I am thinking maybe o2 sensors, but would that cause such a major missing problem? Opti?

dmoor88

one or both of the O2's are bad. if one is bad, the other will run lean, telling the computer to compensate by running overly rich. in open loop, the pcm isnt reading from the O2's yet.

chrism400

Ditto with the above post. He has obviously been through this too. I just changed my plugs, wires, opti, coil. Still was running rich and stumbling. Turns out that my rt O2 was bad. Threw the whole thing out of whack. Every one of my plugs was carbon fouled making everything worse. I even changed my injectors back to the stock ones and stock pcm just to see if there was something wrong with the computer or new injectors. It finally threw a soft code that I was able to read. Been there man! Good luck!

93ZM6Tally

Had a similiar problem with O2 sensors and my coated Hooker LT's. Turns out the O2's were never getting to the correct operating temperature, and were giving the computer erroneous information. Bought some extension kits, ran a couple of extra wires, problem solved.

Bocefus

I was able to install the driver side O2, but couldn't remove the passenger side O2 since I didn't have adequate leverage to twist it off with the tools I had on hand. I ended up taking it to the dealership who installed the O2 sensor and a fuel filter. That did not fix the problem so they diagnosed it further and they say it is the Opti. They priced the Opti at $630 and the install at $180. I'll be ordering the Opti through Val at VanDevere and have the dealership install it. $180 sounds like a reasonable price to have someone change the Opti out in my opinion. Thanks for the help.

slopokrodrigez

Don't be surprised if the price to install it goes up IF they even take the job when you show up with your self purchased opti. And they probably won't guarantee anything regarding the job.

BTW, considering the dealers desire to boost the bottom line, I wouldn't buy anything until I or someone other than the dealer checked a few things. My very dear friend (a snap-on dealer) is sick from hearing the mechanics at dealerships boast of having gotten this customer or that customer for x and such part.

Why would the opti be a the problem only after it warms up? If it were a spark issue, I would expect the coil or ICM to be the problem after warm up. Sounds like fishing to me.

Dave

93ZM6Tally

Dealership troubleshooting process. Replace parts until the problem or the customer goes away. All at your expense of course.

Bocefus

Those *****....

They just tried to con me into a $630 Opti plus labor.

The O2 sensor fixed the problem. I just got done driving the car home and the problem is GONE. I was suspicious all along. Those ***** tried to rip me off.

jchevy

If it was O2's you problem should clear up if you go WOT. If its not, i would look elsewhere. Unless 93's are different, which i dont think they are.

Bocefus

Are you saying I should be able to go WOT even if the O2s are bad? When I went WOT, it would cut out completely. Even going 1/4 throttle would make it cut out. But now that they installed the passenger side O2 sensor and fuel filter, it runs fine. I ran it for 20-30 miles with no problems at all, so I think its fixed. Before, it would barely run after it was warmed up. I do hope you are not correct and my problem won't reoccur.

jchevy

Going WOT changes the PCM to Power Enrichment mode which is essentially open loop and does not take a reading from the O2 sensors. Maybe the 93's are different or i am just wrong all together.

93ZM6Tally

Nope, you are correct, O2's are not used at WOT, even on 93's.

DonHood

I had the same prob a while back. Car would run extremely rich when in closed loop, and would barely run when at partial throttle when under load. WOT was fine up untill about 3500-4000 rpm when it would barely pull anymore. Replaced the O2 sensor that was giving me trouble, and all the probs went away. I know the O2's arent' used for fuel calculation when at WOT, but they're still monitored, as you can watch them with any data logging/monitoring software. They must be still used for something since replacing them fixed my high RPM, WOT stumble as well.