chevyboy91188

iTrader: (15)

Ok I know someone has had this problem before but I looked up the code vis search and I didn't get an definitive answers.

SO I got code P0507 which is idle rpm high.

When I start the car it revs to about 1800 then it slows down in steps and comes to rest around 800 and 600 in gear.

When I go to accelerate I have some intermittent stumbling up to 4000rpm then the thing takes off.

I have been told that it is most likely vacuum leak because after 4000rpm the engine runs just off the MAF only.

I had to take of the intake because a broken MAP sensors tip fell in. SO I took off the intake and got the piece out and then put the intake back on. For the first day or two all I felt was a slight extra pick up after 4000rpm and I didn't think anything up. Then It developed into a stumble and now its happening at the low rpms like i said. SO it keeps getting worse it seems.

I tried checking with propane at idle around all gaskets and hoses but get nothing out of the engine as far as idle changes go.

Can anyone recommend another course of action to me?

Intake gaskets are reusable on the ls motors right?

any idea why it would keep getting worse?

do the gaskets sometimes not fit the same the second time they are put on? or could they move out of place?

anything helps thanks a bunch

LS1-450

iTrader: (33)

Yah, probably an intake gasket leak or if the MAP sensor connection isn't sealed properly, since the break, it could be the problem. Regardless, from what's been described, it sounds like the conditions & the symptoms point toward an intake leak somewhere.

chevyboy91188

iTrader: (15)

I replaced the other map sensor with a brand new one, does the map sensor have to be clipped down to work properly? Because when the map sensor got broken off so did the clip that it goes on. It plugs in good and tight with the rubber grommet on the map sensor iteslf, but could it having the freedom to move in and out ever so slightly cause the engine to stumble? Or as you said is it more likely to be the intake gaskets not sealed correctly from when I took the intake off? Is there anything that promotes air tight gasket sealing? Like a lube or spray?

LS1-450

iTrader: (33)

Check the MAP sensor & yes, find a way to hold it in place. Just sticking it in the hole w/no clip is not advised. It can wriggle out. Pull the intake off & look & the gaskets. Make sure that none of them are pinched, cut or otherwise not where they are supposed to be. I usually put silicone @ the bottom of all of the intake runner gaskets, just in case, but really, it shouldn't be required. Might be something you want to try. Also check the throttle body gasket & the fuel injector "o"-rings.

chevyboy91188

iTrader: (15)

ok. im thinking about having it smoke tested to cut down on the troublshooting. I have a place where I can have it done cheap. that "should" find my problem i hope. if not im going to be doing everything you said

gofastwclass

iTrader: (2)

...Do you have the brake booster vacuum line plugged in? What about the vacuum line for the heater controls? They are both on the back of the intake and depending on the car may be difficult to see or reach.

chevyboy91188

iTrader: (15)

I have the brake booster connected, but what is this heater vacuum hose? Is that on the back of the truck intake?

Indyjc

iTrader: (1)

I've got the same problem, checked my vacum lines,replaced intake gaskets,tps,iac,map sensor,tb gasket,no carbon build up,throttle cable not to tight,throttle blade closes all the way. Talked to a gm tech. Sat. nite he said to replace the pcv with a delco unit. After that I don't know what else to do. Good luck. Please post up your findings.

chevyboy91188

iTrader: (15)

did yours develop over a few days like mine did?

Indyjc

iTrader: (1)

I really don't know when mine started. I should have been more clear, my symptoms are a little different. My car runs fine till I stop for gas start it and take off it runs like crap for about 5 sec. then runs fine. On start up it idles to about 1,ooo rpm then settles to about 650 rpm. I want to put a cam in my car this winter and have a tune done, and I want to fix any issues with the car.

chevyboy91188

iTrader: (15)

oh ok so a little different. mine only acts up if i get on it which is why i think its a vacuum leak besides the idles creeping around when i first start it to find its happy spot

chevyboy91188

iTrader: (15)

ok so I just wanted to update this post with my solution I was low on fuel and my gage wasn't working right so the stumble was the fuel sloshing lol but I'm still getting the code but it doesn't affect my performance it just searches a little for the good idle spot when I start it, but I don't know how to correct that.

any one know how to make the pcm learn the correct idle rpm when using a th350 setup?