: Help! 96 STS Stalling and Barely Drives



johnyhuh
01-27-04, 11:49 AM
Help!

I have a 96 STS with 118,000 miles on it.
The car ran perfect until I discovered a fuel leak in the plastic fuel rail last week. I replaced the fuel rail last night. I took apart throttle assembly to get the fuel rail out and found Oil and grime all inside the throttle and intake. I cleaned out as much of the gunk as possible. I replaced and reinstalled the new fuel rail and injectors (careful to keep everything clean.) I then reinstalled the Throttle body. All hoses and harnesses were put back in place.

When I started the car I noticed that the engine seemed as if the running on 4 cylenders and idleing very rough. I drove the car and it ran terrible from a stop but seemed normal at higher speeds. After a 5 minutes of driving the Check Engine light flased on and off, then remained on. A minute later the DIC flashed, SERVICE EMISSION SYSTEM. The car ran a little better after this message appeared (like the computer bypassed something.) I ran the diognostic codes and found Low voltage on the O2 sensors and an engine misfire history.

I don't know where to start. Should I replace the O2 sensors? Or is there something I am missing here.

onecad
01-27-04, 01:20 PM
I've read many posts about this, and I would say if thats the message you are getting then its most likely to be the problem. If these O2 sensors are not running properly then the car will run rough, but will go into limp mode to help the car reach its destination point. So don't run the car too much without rectifying the problem. Do a search in this forum on o2 sensors and you will see what other people have ran into, there is lots of talk on them, the sensors are different also for each exhaust manifold so if when you buy them make sure you put the right ones in the right spot.

good luck

zonie77
01-27-04, 01:30 PM
Was it running good before you replaced the rail for a leak?

If that's correct then I would go over the area you worked on. It's probable something didn't go together right to cause the change. Don't change the O2 sensor yet.

Anthony Cipriano
01-27-04, 02:41 PM
Help!

I have a 96 STS with 118,000 miles on it.
The car ran perfect until I discovered a fuel leak in the plastic fuel rail last week. I replaced the fuel rail last night. I took apart throttle assembly to get the fuel rail out and found Oil and grime all inside the throttle and intake. I cleaned out as much of the gunk as possible. I replaced and reinstalled the new fuel rail and injectors (careful to keep everything clean.) I then reinstalled the Throttle body. All hoses and harnesses were put back in place.

When I started the car I noticed that the engine seemed as if the running on 4 cylenders and idleing very rough. I drove the car and it ran terrible from a stop but seemed normal at higher speeds. After a 5 minutes of driving the Check Engine light flased on and off, then remained on. A minute later the DIC flashed, SERVICE EMISSION SYSTEM. The car ran a little better after this message appeared (like the computer bypassed something.) I ran the diognostic codes and found Low voltage on the O2 sensors and an engine misfire history.

I don't know where to start. Should I replace the O2 sensors? Or is there something I am missing here.


I think you're missing the fact that if the car ran fine before you took it apart then whatever you worked on is likely the problem. I know it's hard to accept the fact that something didn't go back together correctly, but - something didn't go back together correctly. I doubt that the oxygen sensor or anything died while you were working on it. And the oxygen sensor will not cause the engine to drop 4 cylinders or enter into any sort of "limp mode" that drops cylinders. If you left injectors disconnected inadvertently or something like that it would cause an O2 problem as the O2 wouldn't be reacting to preprogrammed test parameters. That wouldn't mean that the O2 is bad. The code is just a clue that something regarding the fueling is incorrect. Since the injectors were "touched" I would go to them first.

Check the electrical connectors at the injector to make sure a pin wasn't bent and "bypassed" in the process of reconnecting them and check the jumper harness connection to the injectors if that was disconnected. Cleaning out the intake was pointless. It will be grimy and "oily" again shortly. That is what happens to "dry" intakes on port fuel injected engines with EGR being introduced into the intake. The EGR causes a lot of the soot and "grime" you report. Perfectly normal.

Just clean the throttle body around the perimeter of the bore where the throttle blade contacts it to prevent any throttle sticking off idle and quit worrying about it.

It sounds like you have some of the injector leads crossed or not connected correctly. If the manifold went back on correctly and there's no vacuum leak then I would double check the electrical connections to the injectors first.

johnyhuh
01-27-04, 04:03 PM
Thanks for the help everyone! I'll have to go back and see what is going on. Point well made on the O2 sensors. I don't want to replace them if I don't have to. I'll go over all the connections again. I did notice that the injector harness wire were a bit brittle. Would having the sparkplug wires too close to the injector wire cause anything? The spark plug wires are only 8 months old. Also, can perement engine damage occur if the engine was running on limp mode?

johnyhuh
01-27-04, 08:31 PM
Ok here is the latest. Anthony Cipriano was right! I had the injector wired backwards! Wow, what a difference when things are wired right. I rewired the injectors and disconnected the battery to reset the computer. The car ran great but hessitated a little when I pushed the gas.

However, I still have 2 problems:


When I start the car after sitting for 2 minutes it seems to want to crank for a while until it finally starts, (like there is no fuel)
After driving the car for about 10 min the CHECK ENGINE light came on and the SERVICE EMISSION SYSTEM came on the DIC. I ran the codes again and the pc0131 (heated o2, low volt) came up.
What could this mean? Bad Injector, O2, something I am missing again?

Aurora By Olds
01-27-04, 09:37 PM
Another thing to remember is that a flashing SES light means Cylinder Misfire. Knowing that, it would have pointed right to your injectors.

DaveSmed
01-28-04, 12:32 AM
What did you use to clean out the intake? Some stuff can coat the O2 sensor.

Ralph
01-28-04, 12:56 AM
Could it be when you blew out the fuel rail, you didn't just dislodge some of the crud, and now it's in a different area haunting you? Or some debris that got shifted around concerning your injectors.

johnyhuh
01-28-04, 09:59 AM
Problems solved! It turns out that the fuel pressure regulator was bad. This could be from the old leaky fuel rail. I replaced the fuel pressure regulator with a new one and now all is well. Reset the ECM and the codes are gone. The car is now running great!

As for all the gunk in the intake, I guess that is normal? I was supprised to see all that crud in there. I'll just have to keep an eye in that area. It's good to know that all of the sensors worked normally. In reaction to my screw ups and a failed part.

This project took some time and frustration but saved me about a $900 doing it my self rather than getting ripped off at the dealership. I even saved money buying the part online. The new fuel rail at the local Cadillac dealership was $350 bucks as opposed to the $150 part I purchased on line (both same GM part.) This forum is the best! Thanks everyone for the support!