therabidweasel

iTrader: (5)

The whole brake thing would seem to be a clue. To what I don't know though. Id spray some brake cleaner over by the booster vac connection first. It's gotta be in that area. It has to be vacuum, can't see how the tb would be affected by braking.

omgitsmikeyc

I'm thinking it's a vacuum thing too given its not a voltage thing. ( the ac/fan questions leads me to that given uta not dropping when drawing the most power.) could still be an ecu program issue.

senicalj4579

iTrader: (41)

My car is acting somewhat the same after getting it back from a h c i job. Let off the throttle at 45mph and rpms stay around 1500rpm. It acts like cruise control.
If im at a dead stop ill let off the brake and the car will start moving.

demonspeed

iTrader: (7)

I'm having a similar issue -- Cold start idle's around 900, and after driving it will idle up to 1000+. It also takes forever to idle down when putting the clutch in.

I don't remember what my old LS1's idled at, but this seems too high. I do have a Potz ported TB; however, it did not do this immediately after installing it.

427LS7HCI

What turned out to be the issue?

adamantium

iTrader: (3)

Have no clue. Ive noticed when i shut it off it makes a hissing noise way after the car is off coming from the rear pass side of the engine. Vacuum leak back there? This is annoying. Ill go to the autozone later or something get some starter fluid and spray it everywhere to see whats up, if not im just going to go tune it. Im sort of sick and tired of this car, almost every other day its an issue.

adamantium

iTrader: (3)

Just got back from the autozone got starter fluid sprayed it along the WHOLE PCV system and no changes in idle. Im pretty positive this thing just needs a tune. Ill be tuning soon then.

I was holding off on tuning since i thought i had a vacuum leak, but idk why people keep suggesting its a vacuum leak, a vacuum leak is constant.

Why would the car return to idle if it was a vacuum leak?

adamantium

iTrader: (3)

..........

therabidweasel

iTrader: (5)

Why would the car return to idle when you hit the brake? The only relationship would seem to be vacuum and maybe the brake flicks the map enough to get a response. I'm out of my depth on this suggestion. It would seem that you've eliminated the vacuum leak though.

RevGTO

iTrader: (12)

A couple of things. First, have you disconnected your battery or reflashed your PCM? If so, this will cause the PCM to have to relearn its idle settings and the result is hanging idle. Second, there is a solenoid on the driver side of the intake manifold that has one vac line going to the MAP sensor (on the back of the intake) and another vac port for AIR. You have to cap that one off if it's not.

A couple of months ago, my car started this behavior for no apparent reason and I could never diagnose it. It gradually went away after a period of a couple of months. Here's a thread I started about it: https://ls1tech.com/forums/pcm-diagn...ghlight=cruise

adamantium

iTrader: (3)

Thanks i saw your thread, and last night it seemed to not do it as much.

Is this the hose you are refering too?



If so i plugged one of the ends of this line with a thick screw and some epoxy.

The car seems to be doing it less and less, also i still have SES light for both o2 sensors, i think i need a tune.

RevGTO

iTrader: (12)

Yes, but that one should still be attached. Did you remove the solenoid?

And the O2 sensor issue probably won't be solved by tuning.

adamantium

iTrader: (3)

Yes i removed the solenoid. Do i need the solenoid for anything?

RevGTO

iTrader: (12)

No, you dont need it, but it makes keeping vacuum more difficult with it off. With it on, all you need to do is put a cap on that lower port on the solenoid.

adamantium

iTrader: (3)

Damn this sucks, so what do you recommend i do? Now that its plugged off with epoxy i kinda can't turn back now.

RevGTO

iTrader: (12)

Yep, I'd just stick with what you've done and give it some time to see if the issue starts to improve. As in my case, if you've cured any possible vacuum leak, it may get better over time. But it takes a while.

adamantium

iTrader: (3)

Thanks for chiming in man means alot! Ill just wait it out. My tuner is semi positive its a tuning issue.

Sladester2

iTrader: (1)

I think its with the tune honestly. Mine doesnt change with the brake though.

adamantium

iTrader: (3)

Yeah my car idles fine as soon as i get to a dead stop, i think my car never really relearned the idle since the o2s are shot. To be honest your issue sounds vacuum leak related, try spraying starter fluid all on the PCV system and or intake, TB or any place where there WOULD be a vacuum leak. Is it consistent?

caturnbull1

iTrader: (2)

i know this is a old thread but adamantium did you ever fix the problem? my car is doing the same thing.