So like an idiot I bought a car a few months back from a guy that has some obvious misfiring before checking it out.

The car is a 2002 SS camaro, Since buying the car, I took it to get tuned and my guy noticed a crack in the the Intake Manifold, the car was set up to run NOS at one point but I currently dont have a bottle. At this point the begining of a long list of repairs began

1. replaces the LS6 intake manifold as it had a crack in from where they banged on the fuel rail.
It was still misfiring insanely after this,( if not worse), so at the advisement of my tech I replaced the following:

1. Full Diagnositc resulted in little results. (:-()
2. Plugs and wires, NGK plugs, performance wires
3. New O2 sensors and and extenders as they would not fit around my headers.

After installing these and thinking the problem was fixed the left bank was still running extremely rich, so we tuned it to compensate as best as possible but concluded there is still an exhaust leak somewhere. While he was tuning it he shut down certain cylinders to see if he could detect something, ( not sure what) , and noticed the engine was not throwing any codes at all, as it should have been.

He told me that my computer was shot and that it needed to be replaced so that was another $250.00 for him to install a refurbished one he had at the shop and load the appropriate programs etc.

In the process of figuring all of this out, the Service Engine Soon light flashes. The car runs decent but there is a obvious misfire. We checked all of the cylinders and cylinder 6 had little to no change when turned off with the tuner and cylinder 8 had Absolutely no change when turned off on the tuner.

at this point it was 6 at night and my guy suggested that I change the injectors cause that was probably the problem. $200 and a hour later, we installed some LS6 injectors on the car, (finding out i had LS6 injectors in the first place). and the car ran EXACTLY the same. I drove it home, about 20 miles and the light was flashing the whole time, I do feel a slight misfire but nothing like it was before which was pretty much undriveable.


from reading the forums and talking to the tech he thinks it could be one of the following

1. Cylinder 8 Coil needs to be replaced?
2. Possibly just a dead cylinder

The strangest part is, even as it misfires and SES flashes it still continues to throw NO CODES, so I have absolutely no idea where to go from here. Im over budget, tired, and discouraged. Any thoughts or help is appreciated.

 

Definitely try to get the coils tested. You sure all the grounds are connected properly? Clean the maf, check the vacuum lines, and are you sure your getting good fuel pressure at the rails and under load? An exhaust leak will make it run rich on one side you definitely need to find where it is leaking at.

 

Maf sensor readings are good, I feel like if it was a fuel pressure issue my tech would have seen it. I'll look at getting the coils checked out and mention the grounds and vacuum lines. Thanks.

 

whose ur tuner? where you located at?

 

I'd question your tech if he is changing stuff out, charging you for it, and it doesn't help. If it was an injector it would be very easy to diagnose by pulling the plug off of the injectors one at a time.

 

Im in San diego, took it to excelsior motorsports, his name is krishan. Yeah I don't know about testing the injectors, I'm new to a lot of this :-/. Does it sound like if could be the coil?

 

You need a new tech! I'm an ASE certified tech with about 9 yrs in the field. It's not that hard to diagnose a misfire and absolutely no need to throw a bunch of expensive parts at a car. Determining which cylinders were misfiring would be the first step. Checking compression on the misfiring cylinders would be next. If compression is good, start swapping ignition parts and injectors to see if the misfire follows the part.

If compression is bad you need to use a leak down gauge to find out why. Burnt or bent valve, leaking rings, blown head gasket, broken valve spring, etc. If compression is good you could still have a flat cam lobe or something. You could even have good leak down but bad compression if you had a bent rod.

Bottom line, you need a guy that knows what he's doing and will quit wasting your money.

 

^^^ what he said. also check your coils

 

Man your mechanic is taking you for a ride.

 

Easiest way to check any ignition part or injector is to move it to another cylinder and see if the misfire follows the part. I'm pissed your guy threw a whole set of injectors at it without trying to verify you needed any. Of course to do any parts swapping you need to figure out which cylinders are misfiring first.

It's very possible to have a misfire and no codes but if the SES light is flashing there has to be codes stored. Lots of codes will set the light, only a few make it flash. Misfire codes are the main ones that will make it flash because a misfire can destroy a cat and the whole purpose of on board diagnostics is all about emissions.

My advice would be unplug each injector one at a time with the engine idling. The RPMs should drop. Any one you unplug that doesn't cause a drop isn't firing properly. Find the misfiring cylinders and let us know, then we can go from there.

 

Couldn't have said it better. Oh this is what's wrong, that'll be $200 please. Oh actually this is broken, that'll be $250. Dunno where you spent $2500 on a manifold, plugs, wires, o2 sensors, PCM and injectors.

Sorry I couldn't help, but several people have mentioned exactly what to do without just replacing random parts and hoping that solves the problem.

 

I do want to give my tech some credit because when I brought him the car it was kind of a wreck. We actually tested all of the cylinders by turning them off manually with the computer and the only one that didnt cause the engine to bog down was the 8th cylinder, I know the next part is to check my coils but being that I am out of money for the most part right now I just ordered a coil off of the internet that i am going to replace myself to see if that helps at all.

Also, I dont have cats, I am running straight pipes.

Lastly, I know the engine SHOULD be throwing codes, but I think the people who had the car before me did some pretty serious gutting of the car because we replaced the computer and its still providing nothing.

I am pretty frustrated to have paid $2500 in parts and labor so far and come up with very little towards fixing my car. what should be my next step if the coil doesnt fix the problem>? compression check? thanks everyone.

 

You need a better mechanic.

 

Honestly man I wouldn't have even bought a new coil until you verified it was bad. First check for spark on that cylinder. If you don't have spark, It's as easy as swapping the coil with another cylinder to test the coil. If the misfire follows the coil then the coil is bad, if not then the coil is good.

I don't remember what all you said you replaced, but if the coil doesn't fix it, try swapping plugs and see if it follows the plug, then try wires. Even if parts are new I wouldn't assume they are good until I'd verified it. It's easy enough to swap ignitions parts on these engines from cylinder to cylinder.

If you verify all ignition components are good, or if you had spark to begin with then check compression.

You can also swap injectors with another cylinder to make sure you have a good injector on that cylinder.

 

I have replaced the plugs, wires, o2 sensors, injectors, computer, and intake manifold. at this point a compression check and testing the coils will be next, i might try and dig into the coil problem tonight when i get back from school, but I am going to have to take it in to get the compression tested.

So if i disconnect the cylinder 8 and nothing happens, and then switch 7/8 coils and disconnect 8 and rpm decreases, then its my coil, assuming 7 does nothing when disconnected right?

 

Yep. Like I said though, check spark first. No point swapping ignition parts if you have good spark.

 

I would tell your so called tech he is a moron. Honest i don't know how some of these guys get jobs when they know nothing more than oil changes and brake jobs.Op look on tech for a group in your area,im sure someone knows somebody that can help you out that knows what they are doing

 

Previous owner probably bounced the rev limiter a few times and you have bent valves.

.

 

any "tech" should be able to pop the hood and pull the plugs off of the injectors to check if a cylinder is firing or not. this takes all of a minute and a half. no credit from me.

 

Just get a laser temp guage or just touch it with your fingers real fast. If you start a cold engine you'll know if one is not firing in 5 seconds of it running by touching each pipe. It'll stay cold and the others will melt depleted uranium.

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