it's called a burnt piston or valve.

 

What are the symptoms of a burnt piston or valve?

 

the exact thing your describing.

 

Like I said earlier in this post, I had the same problem but it was because of a screwed up aftermarket throttle body. Did exactly what you are explaining, put my stock throttle body back on and the problem went away. Never threw a code or anything. But you're using a stock throttle body right?

 

Yes stock throttle body, I dont know how I could have burned a piston or valve, I raced my friend's ls1 after I started having this idle problem and I can still beat him (without bottle) and we are both stock. If i had a burnt piston or valve, wouldn't my car lag? Wouldn't my car become slower? My car runs fine except for that problem. It tends to accelerate itself, like if the car thinks its leans and is overcompensating it with fuel.

 

Ok I havent read all this but Im going to throw this out there.
You are the same one that had the nozzle screwed into the egr port on the intake right? And you also had burnt spark plugs right?
If so take and do a compression test and a leak down test on the car.This will tell you what you need to know.Feel free to hit me up for help if you need it.
Dave

 

No Dave, I followed installation according to the NX manual. My spark plugs are not burnt, they are in good condition. And I do not have the nozzle screwed to the EGR port. I have it screwed to the plactic/rubber tubing that conects the filter&MAF assembly to the Throttle Body as the NX directions indicate. After spraying nitrous at the track, something messed up on a 1/4 mile pass. I heard a little pop, and from then on, my idle is all messed up, my car does not rev like it used to, it takes a long time for RPMs to come back down. The engine shakes violently at idle and the car sounds like it has a huge aftermarket camshaft. On cold starts, the engine idles so low that it turns off. The car seems to run fine once it is in gear and under load, although when the car reaches its running temperature, it likes to accerlate on it's own without me touching the accelerator, even in gear. I switched Throttle Position sensor with an LS1 buddy, but no improvement. I'm going to try and have the car scanned again tomarrow to see what codes it throws out. I really don't know what could be wrong with it. 68maro says I have a burnt piston or valve. But stock I can still beat my buddy on his stock LS1. If the piston or valve was burned, wouldn't the car be slower?

 

pull your breather and check how much blowby your getting, i know when i cracked a piston, i heard a pop/backfire at the top of 4th and i got lots of blowby out of the breather

 

so what the hell was the code? that is the beauty of technology- it takes alot of the guessing out of diagnosing problems. if you know the code then you know what to look at.

it doesn't sound like you burnt something up, if it still pulls hard and you did not mention any smoke.

i agree with jimmyblue on the plastic intake or intake gaskets being blown out. once the car senses something is wrong it throws it into limp mode aka low timing table and it can be pretty damn slow, but what caused this to happen is what you need to know.

again, post up the code and maybe some of these guys can help more, or save up and give it to an experienced mechanic, not one who is going to say " oh you have nitrous? well then it is blown up. nitrous blows up motors... " . get my drift?

also somebody on here offered to come over and help, that may be your best bet.

good luck.

 

Have you run the compression test or leak-down test yet ?? The small pop you heard probably was a small backfire and it blew something out - the intake, throttle body, etc.

 

Ok Isorry I got you confuse with someone else.
Do the following things.
Check plugs.
Compression test.
Leak down test.
This is a for sure way of knowing what is going on.The chances of a pop and then a sensor going out are slim.If you can go ahead and scan the car.But more than likely its time to look at the three things I listed.Let me know if you need any help.
Dave

 

After you do what dave said (you need to make sure the engine is healthy), if that comes out ok, your problem kinda sounds like the the IAC is acting screwy. Rough idle, works fine off idle, rpms slow to come back down, sounds like a IAC problem right?

 

LOL not that was me Dave.


I will say this about this problem though. Back when my car was a cam, header and nitrous car I raced an 03 Cobra and when I sprayed it my N20 solenoid stuck open on me, I didnt have a Window Switch. By the time I got my bottle turned off, it was right behind the seat, it had emptied an entire 10 pound bottle of nitrous into my motor. Well of course the car ran like ****. I replaced all of the plugs and it ran better, couldnt tell at idle really because it was cammed to begin with, but running aorund it felt ok. All motor at the track in ran ok, not as fast as I thought it would but quicker than some others. Decided to do heads on the car and when we pulled the heads off we found a nice big chunk out of piston #7. At that point I felt it best to rebuild, bigger and better of course. Hopefully you didnt do that much damage but think just because you can still beat your buddy that you havent.

 

You might want to check you MAF meter. The same thing happen to me while at the track. The car went lean and I heard a pop. The car ran like Sh*t while at idle and it ran ok once I got into like 3rd gear or higher. The little filter elements were broken. I would not have been able to tell until I look at it HARD then you could see that only ONE of the three elements were broken. Just a thought. ONce I replaced my MAF meter the car ran like a champ. PLease let us know what your final outcome is. Good Luck.

 

Ok just scanned the car. Here are the codes, P0171 and P0174. Based on these codes, I think it is the MAF meter that gave out like Shoulder Shaker said. What do you guys think it could be?

 

P0171 Fuel Trim System Lean (Bank 1)
P0174 Fuel Trim too Lean (Bank 2)

 

I seriously doubt it is a burnt piston or valve. I would however check the elements in the MAF or see if someone has one that you can borrow long enough to check yours out. The other thing I would look for is a vaccum leak. If you had a backfire and it split or blew off a vaccum line you may also experience these issues. Combine both the MAF and a vaccum leak and you will have the exact recipe that you are describing.

BTW kudos to you for trying to work the problem out yourself and learn more about your car. I know it can be tough but if you plan to learn more your car you are on the right track by finding issues as they arise and fixing them yourself. There are allot of us that had to learn the hard way as we didn't have a wonderfull internet BB to help. So keep plugging away and good luck to you.

Jim C.

 

PS- After you find the problem you may want to reset the PCM so as to make sure that it does not stay in "Limp Mode" should it be in such a status. Cheers !!!

Jim C.

 

PSS- Sorry but I forgot to tell you a tip that I learned after a similar experience with a mustang. If you start looking for a vacuum leak you can get a tank of propane with a small diameter hose hooked to it and turn it on slowly then begin to fish the exit end of the hose around the motor. If the motor begins to idle up while you are fishing around it that will be the area the vacuum leak is located in. Hopefully should it be a vacuum leak it will be something simple. Cheers !!!

J

 

Ok just tried swapping MAF meters with my friends LS1. No inprovement, I am also getting a P0300 code. Ruling out the MAF, Im going to say that this is a vacuum leak. It's not going to be easy to find it.