gsasca

I just got my hands on a 2003 Corvette 50th anniversary. Got it out of an auction wrecked. All the body work won't be an issue, but as soon as I turned it on, the engine ran real rough and I had an awful exhaust leak on both manifolds. I put new gaskets in (solving exhaust leak issue), and put all new spark plugs in (runs a bit better now, lost 3 plugs I believe). Everything sounds good, but the motor still runs pretty rough and I get no acceleration. Reading up on some other threads it sounds like it's in limp mode. I have no lights up on the dash.


What I did find is that both sensors on the exhaust manifolds going into the Cats had been unplugged, and they were laying on the pipes, melting them. Would these O2 sensors cause the limp mode? Or is there something else that is causing it? I know I need to replace the sensors and find where they were originally connected, but I'm curious if that will solve my problem.

delta_bratwurst

It is highly likely that the cooked sensors are your problem. The computer needs those sensors to sense if its running rich or lean and adjust accordingly for maximum efficiency and performance. With the sensors not working the computer has no idea how the engine is running. Therefore it will set a predetermined not so great air/fuel ratio in limp home mode. The engine will run, but very poorly.

Replace those sensors!

gsasca

My issue now is finding where they plug in. The previous owner really turned this thing into a Frankenstein car. I cannot, for the life of me, find the female ends of the plugs.

delta_bratwurst

I wont be of much help there because I have never messed with my lower exhaust system. If I had to guess the two wires leading to the sensors should run along the length of the bottom of the car towards the front of the car. They shouldn't be too hard to spot.

Rob 02

There is some heat shielding on the left and right in the tunnel. The O2 sensor wires run along the shield healed on by clips. The engine wiring harness will have a place for them to plug in at the left and right side of the fly wheel bell housing.

Pull all the codes, write them down and post them
You can do this from the dash.
Here is the video that shows how.

gsasca

First I wanna say thank you for that video. Was amazing. I will list the codes in a second. For the O2 sensors, they have a flat 4 pin plug while the females I found were all square 4pin plugs. I'm now guessing those are it and I have to buy adapters, or I just need to buy sensors with proper plugs.

For the codes:
40 BCM:
B2587H
2588H
2592h
2593h

A0-LDCB:
B2282H
2286h
2284h
2262h

A1-RDCM:
B2283h
2285h
2265h
U1064h

A6-SCM:
B0851h
2605h
2607h
2606h
2860h

A lot more codes then I though. Thanks for the help btw! I really hate seeing a potential beauty in such rough shape and want to get it back to as great of condition as I can.

gsasca

Just looked the codes up. It is strange that it isn't giving any 10-PCM codes with how bad it is running and with the sensors being unplugged.

Rob 02

On a stock exhaust there are 4 O2 sensors (2 upstream and 2 downstream). The upstream ones have a flat plug and the downstream ones have a square plug on a larger cable. If I remember correctly, there should be flat plugs on the firewall.

If you have an aftermarket exhaust then the previous owner may have deleted the downstream sensors and had them tuned out of the PCM.

Rob 02

I'm brainstorming here about why your car would be running rough. If it is just at idle, you may have a aftermarket performance cam installed.

Are there any metallic engine noises?

After I rebuilt my engine I fired it up without a MAF or exhaust (no sensors) and it ran fine but had the MAF code.

You have been a member for four years and have only 5 post? You must have had good luck in the past.

Rob 02

The BCM column lock codes worry me a little as they can leave you stranded and is a common issue
There is a device called LMC5 that eliminates it and will solve the problem.

http://www.ebay.com/itm/LMC5-MODULE-...lSbDPu&vxp=mtr

Here's the video

gsasca

The idle isn't that bad (the occasional sputter) it gets bad when you accelerate. There is no power at all. Afterwards the idle gets rougher too, you have to play with the throttle to get it to idle right again. I will try to find the plugs, but the exhaust looks stock to me.

And I had a C4 for a while just recently got the C5.

Rob 02

Here is my guess:
You bought it at a salvage auction and the car was declared a total loss due to a crash.
The previous owner had an expensive aftermarket exhaust and headers. After the crash, the previous owner reinstalled the stock exhaust with the the header gaskets that don't match the stock exhaust manifolds. Specifically the AIR injection tube area of the gasket.

The car may have been sitting a long time with old gas awaiting auction.
What does the gas smell like? If it is rotten it will be obvious.

gsasca

You have a point. The gaskets on both manifolds were bad and none of the bolts were even tight. Gas doesn't smell rotten, but I will definitely look into all of it. Going to have to wait a full week again just to dig back into it.

Rob 02

They may have had the rear (downstream sensors) tuned out if they weren't using cat's.

There is a good chance that the car belonged to a forum member. If so any information would be helpful.

A Car Fax might reveal a few things. I purchased my car from salvage last year and it was stock. I got a Car Fax and called the dealership where it was last serviced. They said that the previous owner had gone through deep enough water to hydro-lock the engine. This was a big help in the restoration.

You may have a bad filter or fuel pump. Check the fuel pressure at the rail.

Rob 02

The later '03 and '04 had an issue with the tube that connects the right and left fuel tanks. The C5 has a tank in front of each rear wheel and the later models had a metal tube connecting them. The tube is known to cause a leak on some of them.

I don't have personal experience with this since mine is an '02, but you can search it, or perhaps someone will chime in.


If there was an aftermarket exhaust installed then that mid-pipe and cats were sitting outside and the cats may have clogged. They could have corroded. Mice or bugs may have built a nest in there. I gutted my pre-cat's (pup cat's). When I did I found out they were a little clogged. It wasn't perfect honey comb material but some white cotton like material. I cleaned the main cats out with soap and water then blew them out with a leaf blower and a shop vac on the other end.

A few things to look at.

lionelhutz

On my car, the upstream flat connectors are in the same harness as the downstream square connectors. On each side, they come down out of the main harnesses bundled together and then split just before the connectors. They were also attached to the inner frame structure right beside each other.

gsasca

What is the fuel pressure supposed to be?

After looking at it again, I am pretty convinced that they took off the custom headers and exhaust and put the originals back on.

Mine also has the sensors coming off the main wire harness. It back sensors are plugged in up front with a cable running back to the sensors. I need to buy the female flat plug for the front O2's and that should solve it (I'll be doing some eBay shopping in a bit for them). Once those come in, I will look at fuel pump and lines if the issue isn't fixed.

Here is a picture of the car. Got it in Dallas, TX.

Rob 02

58psi a idle and increases with throttle.

The body damage should buff out. LOL

You could bolt on red body panels with that color code fairly easily. You could go custom hood and bumper but there usually are fitment issues with aftermarket body parts.

Rob 02

If you plan on keeping it I would get the factory service manuals. Used copies always seem to be available. Mine has paid for itself many times over.

gsasca

Already bought all the parts I need. Found a red one at a salvage yard in Dallas and got everything I needed for pretty cheap. Thankfully that means all OEM parts, so all I'm worried about now is getting it running right!