bmccrary

Ok, I know that LT1's have always had a bit of a rough idle, but I think mine is getting pretty bad.

I just had a 160 thermostat put in when a shop replaced my intake gasket. They cleaned my MAF and the inside of the TB as well as the intake manifold. The idle seemed to smooth out after that, but it seems to be back.
The car idles around 500 to 600 on my tach, I am not sure if that is a bit low or not.

Sometimes when I come to stop lights the car will idle at 1000 for a sec then drop down to 500 or so. You can hear the motor stutering a bit as well, it almost sounds like I have a small aftermarket cam in it...too bad its not true.

When I came home from work today, my roommate came out and we chased an exaust leak that seems to be a horrible crack in the weld where the back side of the cat connects to the tubing afterwards. We are going to lift the car up and see if that is case once it cools down. I think I might try cleaning the o2 sensors and see what that does as well. Even though they were replaced this summer.

The opti and cap as well as plugs and wires were replaced a little over a year ago. The car runs too darn well to be something major. It is just at idle. It hasn't cut off on me, yet. It just concerns me.

Any ideas?

-bryan

DroppedM6Z

iTrader: (5)

i'd get under there and check your plug wires and maybe change your plugs if it's time. Lt1's "rough" idle is not like that at all. They seem to have very little shake to them with a stock tune but many can tune it out.

bmccrary

Isn't there a took I can hook up that will tell me if a cylinder is misfiring? I really hope this isnt what the case is, but we will see I guess. I wonder if I can rent a test light or anything from autozone or similar parts stores?

Any other ideas?

-bryan

transam5.7lt1

iTrader: (18)

If its lighting up the SES light, have it tested, could be your IAC valve... auto parts stores can test it for free, they even sell a scanner for this year for about 30 dollars...

bmccrary

Oh, I forgot to mention that it hasn't thrown any codes. The SES has not come on. I will try to get some clips of it tomorrow afternoon, and maybe that will help.

Now that I think about it I have only seen the SES light twice ever and that was after the rocket scientists my father and I were... washed the engine bay with a water hose and engine bright. (Didn't know about the opti issues at the time )

I won't be able to do anything till after next weekend. I am going to Indy next weekend, and I have two tests to take before I leave. So all my time will burnt up with schoolwork and work. So all the help I can get in the meantime will be greatly appreciated.

Thanks

-bryan

bmccrary

I just thought about something. It might a vacume leak as well. Is there a way to test this, or see how much of a vacume I have on the system?

Thanks

-bryan

Ralls

iTrader: (32)

Yes, it's very easy to test a vacuum leak and I think you should. Go to your parts store and buy a vacuum guage with some small tubing. Hook it up to the vacuum feed ( http://shbox.com/1/egr1.jpg ) for EGR solenoid. When the car is fully warm, it should be 19-20 inches of mercury. You can hook it to any vaccum hose on the intake side, but that location is easy to get to.

bmccrary

Ok, well I look them up online. It seems I can get a vacume/fuel pressure gauge for like 20 bucks. I might go pick one up today, just to have. As for connecting to a vacume line, can't I just hook it up to where the brake booster runs in to the intake?

-bryan

Ralls

iTrader: (32)

Yes, you can hook it to the brake booster line. However, the tubing is usually to larger for the fittings on the guage. I wanted to do this too, but its just to big.

bmccrary

Well I went to the autoparts store and picked up a vacume tester. This one is a vacume and fuel pump pressure gauge.



I also picked up a PCV valve, considering I don't think I have ever changed it.

I took a video, but it is too large for you tube. So I might have to get one of it later.

I think this gauge will work in the brake booster because of that one large fitting it came with. I am about to go out after eating some food and try it out.

I will let you know what it reads

-bryan

bmccrary

Ok so I just went out and tested the vacume on the car. We that largest fitting was too large, so I had to some cutting on it to get it into the vacume line to the brake booster. When the car started up at jumped to 22 or so, then slowly went down to 19 or so and held there. When I reved the car up it would back off to 10 or 15 quickly then jump to 25 and stay there until I let off. So I am guessing the vacume is good.

However.. I went to change the PCV valve, which to my understanding is supposed to be right here.


However, this is what was in there.

It is just a just a peice of elboe tubing. Nothing is in there? There was oil all over it and in that line. (runs to to the intake manifold. No wonder it was so nasty in the manifold) That PCV valve is too small and the wrong shape...


Am I wrong in all this. Please tell me I am an idiot and looking in the wrong place because I am very confused right now.

I believe I will be running a seperator now in that line, once this is all done.

-bryan

Sgt. Spuds

iTrader: (1)

Your pcv valve is on the otherside of the intake, points straight in...

Ralls

iTrader: (32)

Your vacuum is good. It should go to 10 or 15 with little throttle. And if you bump the throttle, it should bounce off 0 ''Hg.

bmccrary

Ok, well I didnt hit to hard, just a quick blip as I call it. I will into finding that pcv valve, I feel like a moron. Oh well. I am looking now into doing that seperator. That will be my next thing. Has anyone else ran one of these? Some of my buddies with LS1's run them. After seeing all that in that line, it has me thinking about it.



-bryan

VanbibberLt1

its dead in the middle of the intake manifold on the drivers side, right before the vaccum lines

bmccrary

I found it, but with all the other lines in the way it is very difficult to get out. I might try again later, I just did not want to mess up any other lines around the area.

However I have a feeling that my idle issue is not being caused by the PCV... any other ideas?

Vacume has been checked off the list...

-bryah

VanbibberLt1

dont worry about the other lines, they shouldnt break or anything. getting the old pcv off is kind of a pain, at least mine was.

how old are the plugs?

bmccrary

Ok, the PCV looks like crap from the out side. Some corrosion and such from what I can see.

The plugs are only a year old or so. Maybe 10,000 miles on them, tops. I know the car is running a bit rich but I don't think they are bad. I know that the oil intake leak was leaking all over the back side of the motor. It might not hurt to replace wires on the back side of the motor. But I wouldn't think the oil would mess with them that bad.

-bryan

bmccrary

ttt....

Ralls

iTrader: (32)

Motor mounts might be shot. Bad motor mounts or solid ones can be rough at certain RPMs. Like it can be bad at idle but totally fine when you bring the rpms up a hair.