the propane tank is kinda overkill to find a vacuum leak. get some carb cleaner and spray where ever you can think of that could be leaking (where all the parts meet each other, and hoses).

 

Ok finally some success! After swapping with my friend's MAF meter I was still having the same problem. However, while we were checking the throttle body, we turned on the car with the MAF disconected and the car's rough camming condition stopped (engine stopped shaking violently). We noticed that connecting the MAF back on would make the engine start shaking violently and stumble the idle to the point of almost turning off. Car runs way better with the MAF disconnected but now my idle is still high. Any suggestions?

 

The propane tank works better than carb cleaner does particularly when it could be a cracked vacuum hose and located on the bottom side of the hose. Also, carb cleaner is more dense than propane.

Jim C.

 

Have you tried resetting the PCM with the new MAF?

 

When u fix it, youre in for a big suprise.

 

sounds like you know what's wrong?

 

I had the same surging idle problem as u described.... in gear and driving it would be fine but as soon as u pushed in the clutch or were in neutral the rpm's would shoot up and after awhile would drop down a little bit. This happened after installing my LSX intake manifold and P/P TB. Ended up being a vacuum hose on the back of the manifolf came loose. Quick and easy way to see if it's a vacuum leak. Turn on your heat and try switching to different vents such as going from the floor to the dash and to defrost. If it's a vacuum leak the vents will stay at the default position and air will not come out of the other vents. Quick and easy way to see if thats your problem. It sounds exactly like what I went threw though.
Good luck!
Bob

 

Big Geek, I tried ressetting the ECU after the new MAF sensor was installed, nothing changed, so I guess I can rule out the MAF even thoiugh the car runs better with it disconnected.

I tried the heater procedure you described, bikeboy1, but the vents shut off after I switch to floor or defrost. So if your theory is correct, it shouldn't be a vacuum leak.

 

I was thinking that maybe I messed up the front O2 sensors. What would happen if the front O2 sensors went bad?

 

Hey I found this,
http://www.ls1.com/forums/showthread...79#post5646779
Do you think this can be my problem? Same codes and same symptoms. I don't know much about the PCV valve, can someone please go into detail?

PS: I know this is a double post and I'm sorry, but I need to get attention to fix this problem and this Thread got lot's of attention before.

 

link doesn't work for me

 

just edited please try again

 

I finally figured out what was wrong, if anyone cares. The intake manifold has a huge crack on it. So that was my vacuum. I found it by spraying started fluid where the manifold meets the block. I noted the car reved as the started fluid was introduced to this area. Anyway, I unbolted it this morning. I'll see if I can post up some pics for you guys tomarrow. I am guessing this happened because of a lean condition while spraying. What intake manifold should I buy that will hold up to nitrous better than the stock one does?

 

So, jimmyblue and I were correct ?? hahaaa, glad you found the issue.

 

now that the problem is found, what caused it? incorrect jetting. say 150 n2o pill number with a 100 fuel pill number. makes for way lean. the stock intake will hold up fine. i run 175 and 200 on both cars with stock ls1 intakes.

 

also, make sure the nozzle outlet is pointed at the TB, and not the MAF. it couls also be jets swapped. the n2o jet in the fuel line and vice versa. making it so rich, the fuel puddled and then backfired.

 

This is pretty interesting.

 

Sorry guys, haven't been able to post up pics because of work, but I will post them up this evening. I have been doing some research and I think I should go with the Weiand Intake. Although it's alluminum design is 10lbs heavier than stock, I'm sure it can hold up more than a plastic intake can. I'm not too worried about heat soaking since the air the goes by there passes through so fast.

 

I think moving up to the aluminum intake is somewhat overkill for your application. I'd say probably 90% of the LS1 nitrous users out here are using stock or aftermarket plastic intakes. I've been shooting no less than a 150 shot on my stock plastic intake for about a year now with no problems. I think your intake being cracked is an anomaly. My $0.02, but it's only worth about $0.005.

 

ahem


good deal man. now like stated above, try and figure out why that happened.