Hi guys. I post on LS2 but I've been told the technical information is better here. I have a 2000 Trans Am M6 with 70,000 miles. It's completely stock. I have owned it almost 5 years with little trouble and it is babied. Sorry this is so long, but this is a long story. I'd appreciate any help.

I have had an SES light problem for the last 4 months. I've had misfire codes but my main problem has been oxygen sensors. P0137 and P0157. All oxygen sensors have been replaced.

The car feels weak as hell and according to 3 different mechanics, the oxygen sensors are "working just fine."

I am convinced there is some other problem that is causing these codes as a byproduct but their relationship is spurious. I don't think O2 sensors are my "real" problem. The light comes on at high RPM (5000-5500) and at full throttle.

The engine feels weak and hesitant at lower RPM especially as if it isn't getting enough gas.

It has been to a GM dealership 6 different times (mostly because I'm under extended warranty) and an independent ASE mechanic 5 or 6 times as well.

Here is what has been done:

Injector Flush.
Spark plugs and wires.
Throttle Body Cleaning.
All O2 sensors replaced.
AIR sensors. (not sure if this is the correct terminology)
Replaced PCM.
Replaced Cats under warranty as well.
All other obvious odds and ends.
Fuel pressure is good and the injectors appear to be getting enough fuel to the engine. There are no leaks in the intake or any vacuum leaks.

Even after the plugs and wires, I had a flashing SES light and cylinder 3 and 4 misfired almost 20,000 times between the 2 cylinders. Cylinders 7-8 did as well but not as bad. The plugs and wires are brand new and the work has been checked and rechecked. Coils are fine as well. Misfires don't seem to be an issue anymore. That was just a weird experience.

Despite all this work, the car has stumped 2 dealerships (not surprising) and one good mechanic who I trust. The O2 sensor wires don't appear to be compromised or anything of that sort. Everything has been triple checked. Basically, GM has told me they don't know what to do now and they have been through their infallible "flow chart."

For some reason, they want to "duplicate the problem" as if a mechanic driving my car and seeing for himself that the light comes on will tell them anything. It's just going to be the same old codes and they same old problem. They keep giving me the car back saying "it's fine" and it is nothing short of frustrating. If they can't get the light to come on themselves, they act like there's not a problem.

I wish I had some of you guys looking at my car instead of these imbeciles...

My next step will be taking it to an LS1 shop, I suppose.

Thanks for your input.

 

here is my professional opinion,after the work you explain has been performed i would without a doubt pull the fuel rail and inspect the injectors and fuel rail for rust.I've seen it cause just the problems you descibe many many times.i'll also bet 1 or 2 of the injectors are sticking open at times.someone on this board had brandnew injectors(pulls) for sale 10 dollars each.the important thing to check in the injectors is the screens.

 

if your injectors go bad let me know ill sell you my stock ones i have laying in the garage. i would check the fuel pressure and make sure you are getting proper pressure, about 58 psi at the rail and make sure WOT does not dip low.

 

Also perhaps the coils have gone bad? Just throwing out ideas.

 

Have you missed any gears or mechanically over-revved the enigne (3-2 shifts)

 

=(

The fuel pressure is good, I think it was around 60 and I think the injectors have been inspected. I'm not sure if they have been checked for rust but I know they've been looked at.

I have not missed any gears or anything abusive.

Why am I getting O2 sensor codes though? Am I right when I say that these codes could be caused by something completely unrelated to those stupid sensors?

Also, could this be a problem that never goes away? I'm honestly scared that my LS1 will never be the same again...

Thanks guys.

 

what is the definition of those codes?

 

do what i posted,until they are taken apart and flow tested looking at them means nothing!

 

before he does that he needs to weed out some other issues, i dont imagine its cheap to flow injecotrs, prob be cheaper to buy a new set and just try that

 

you can test them on the car.no need to send then out.but until the screens and ALL the injectors are visually checked for rust,fuel rail checked and each injector tested under pressure how can you go any further?all the symtoms he's posted is screaming fuel injectors.

 

i have another idea you can try.but this may kill the car completely if the problem is rust in the injectors.it will jam them all.go buy a bottle of lucas fuel system treatment,pour the entire bottle in then take the car for a long drive.if its rust the lucas will loosen all the crap in the fuel rail and jam the injectors.if it runs the same its probably not a rust problem.if its rust this will jam the regulator open too.

 

why dont you just swtich the injectors to different cyls and see if the misfire follows. put 2 that are not misfiring on the 2 cyls that are.

 

the idea is not to switch things around but to look at all of them and check them.once this is done you will know if any are clogged or stuck open,leaking,sticky etc

 

well how is he going to test the injectors himself? care to explain on that cause im not really seeing where you are comming from? he could also have a bad injector which will not show up if u do the clean

 

ok i'll try to explain this but honestly i'm not trying to be a smart *** if i have to explain you SHOULd find a pro that has been down this road before.1st test is on the car WITHOUT the car running@ full line pressure.pulse each injector an equal amount of time and observe the line pressure drop from each injector.i would without any hesitation remove the rail and visually inspect the rail and injector screens.then with the raill off the engine i would repeat the drop test and observe the fuel injectors for leakage,spray pattern,sticky,etc.after this its safe to say the injectors are the problem or they are not the problem.i think kartek or someone on here had new pulls cheap.i'm so sure its injectors if it were mine i would pull the rail before i did anything.

 

how do you pulse an individual injector, that is where i wasnt understanding you. for someone who has never done it before and wants to know doesnt mean they shouldnt do it if they have to ask, ive never done a cam install but i did mine and asked lots of questions, questions prevent screw ups

 

i think the info i gave speaks for itself.the dealership should have everything they need to do these tests quickly.if they don't it explains why the car still doesn't run properly.there are plenty of testers available online if someone wants to spend the money.i don't want to suggest anything more on testing these injectors because what i do i understand and know what is safe to do without getting hurt or burning up a injector etc.i would suggest finding a good dealer wrench who knows how to test these injectors and come up with a solid diagnoses.any good gm dealer has these tools and for 1 hr labor should be able to give you a very good idea whats going on with the injectors.the reason i say pull the rail,visually inspect everything is this will without a doubt confirm if rust id present in the system,if it is then you just saved alot of testing.another quick place to look is to pop the fuel line off at the frt of the car where the rubber fuel line attaches to the steel line on the body.look inside the both lines,the steel and rubber line.look for signs of rust.

 

**Update**

If you said, "You might need a new left cat" or "Your cats are bad." You are the winner.

Apparently, the O2 sensor codes were coming on because the cat was failing but not quite bad enough to set that code. They gave me this recording device to hook up to the car while I was driving so they could see more information when the SES light comes on. Of course, I was able to get the light to come on and subsequent to that, the cat failed because the O2 codes were gone and the catalytic converter code was there.

They replaced that and I don't know why but the car runs like a monster now. It made all the difference in the world. It's like I have my car back now. How could just a new cat create such a world of difference in performance? It's like the old cat made my car sick and the new one cured it.

Thanks to everyone for your help and I'll keep you updated if it comes back. I'm so happy because the car feels like it actually has over 300hp now.

 

impossible! a bad cat will have no effect on engine performance,unless it was blocked.how could a cat cause miss fires?sounds fishy to me.but a bad cat COULd be a sign that one or more of the injectors are leaking.

the the rear 02's have no effect on engine performance,they are only there to measure the cats efficiency.

i'm glad your car is fixed,but its sounds like alot of bs. what they did could fix the check engine light.not miss fires though.

 

Possibly BS, but I don't care at this point. As long as the light stays off and it feels like this, I'm happy...

It sounds fishy to me too but the hesitation I was experiencing is COMPLETELY gone and the car feels new again. I know they put the cat on because I can smell the new one. You know the smell.

Anyway, we'll see if it comes back on but the car's performance as definitely changed for the better. It's like night and day. I was shocked.