New member and first post on here to see what various responses I get. First off, I have been dealing with this/these problems for quite some time now and am building up knowledge of the LT1 with all my 'adventures' under the hood.

Majority of the time, after start up I have high idle which tends to stick anywhere between 1100-1400 rpm's. The TB does stick a little and I have done a few things to mess with it. Ranging from constant adjustment of the idle stop screw(which I read doesn't make a huge difference since it needs to be a pcm adjustment) whether that's true or not I have not looked further. Also have taken emery paper and sanded down the ports within the TB slightly to keep the blades from sticking. Little improvement but still tends to stick on the actual TB, it doesn't appear to be because of being dirty however just snagging on body itself and wears a small line/groove in material.

Another problem(s) is my constant hesitation and stutter. At first I thought it was misfiring since the vehicle would shake and shutter like a cylinder was misfiring. After quite a bit of time trying to figure out the problem I'm still stuck on possible O2 problem as the culprit. I was told that an O2 can have problems and create such symptoms and not throw a code, I have no SES light on. It isn't clear whether it is an open or closed loop problem because it seems to do it throughout both, upon start up(open loop) and when the engine is up to temp(closed loop).

So far I have replaced the following throughout my learning experiences with the vehicle: TPS, IAC Valve, MAP sensor, BOTH Coolant temp sensors(WP and Block), PCV Valve, Left bank O2, Plug wires, Re-gapped plugs to .050, Cleaned EGR Valve(working properly), Cleaned MAF, Replaced several coolant hoses, Replaced several vacuum lines which had corrosion and leaks, Did an ICM Cooling Mod...

Basically that sums it up, although I wasn't just shooting in the dark with all the sensors as I did test them correctly and they were faulty or ran low on voltage and signals weren't where they were suppose to be. Now, I am basically looking for any other input so I can build up more opinion and options of what my actual cause or causes may be with this issue. What I am doing this Friday(today) is attempting to verify whether it is in fact an open or closed loop problem or both. I will disconnect the right bank O2 and warm up the engine then take it for a run to check or verify the symptoms and when they occur.

I do wish to add that I also have an intake manifold leak, leaks from the rear and the right bank front corner and this might be creating a vacuum leak along the seal. So with this leak, thoughts are still with possible dirty opti which may need some R&R but I'm looking for other possibilities at this time to avoid the cost and headaches with replacing Opti. Thanks.

 

i went through the same thing with my idle, the more i adjusted it down the higher the idle got. i set the idle up and the computer made adjustments and the idle came down. the tb butterfly is not supposed to be closed all the way. to reset you need to set the computer into dionostic mode which closes the iac motor/valve, once in diogostic mode you unplug the iac so it will not open when you start the car. unhook the scanner or diognostic device used and start the motor. you may have to hold the throttle to keep it running untill you can set the idle at 400 to 450 rpms. shut her off and plug the iac back in. you will most likely have a code for the missing iac so you may wish to clear the codes. i have also had a intake gasket so bad i was losing vacuum

have you tested the fuel pressure yet. changed the fuel filter?

 

Yes I forgot to put that in, I have also changed the fuel filter and air filter. I do still think that the intake could be causing a vacuum problem like you mentioned.

I have not performed an actual check on the fuel pressure though as I am cautious of doing that on my own since it's with the fuel system and I have not read up on how to do it. I have the Haynes manual assisting me just haven't checked into that yet.

The TB doesnt appear to be closed all the way since I can visually see gap with the blades and also since I sanded the ports down slightly. So I am not sure why it still seems to stick and create the visual marks and lines against the TB itself. It literally creates the "pop" sound when I move the blades by hand since it is stuck, still at a loss on how to fix that little ordeal.

Currently the only thing I have to assist me in diagnostics is an ohms/resistance meter, a basic tool obviously. However I do have datamaster and freescan on my computer just haven't purchased the aldl cable yet. Are there any other possibly free diag programs you know of?

 

if its sticking its closing. set it up a bit and see if the computer will adjust it down. takes a bit of driving for it to work at least it did for mine. go here, click on how to and look at 33

 

Unless I'm totally missing an extra post or something I don't think your link posted correctly.

 

dang,,,, sorry bout that. dont know what happened. lets try again.
4th Gen LT1 F-Body Tech Aids

 

Oh yes, Shoebox!!! This man has helped me quite a bit and I am already familiar with his website Thanks. He is a user of the other forum I am on. IDK what your rules are for so called name dropping but I'll go ahead and mention it; camaroz28.com is an awesome forum. Shoebox's site has helped me out a lot, but like I said I didn't look into the whole checking of the fuel system yet.

Today I unhooked the right bank O2 to put the engine in Open Loop and ran it pretty good. The stuttering/shaking I was getting before was gone and the vehicle ran a lot smoother also idled better. I adjusted the stop screw(opened more) until the blades wouldn't stick and eventually the idle came down after running and idles perfectly at 900rpm's. I was told even though it may operate better it still may not necessarily mean the O2 is the problem. I am going to do some further checking into this.

 

are the 02's fouled? you can clean them to a point with a torch just dont get carried away. the heat burns off the black crud. can help or not. mine were so covered they were giving false readings. still do a little but getting the heated 02's helped alot. you should already have heated.

 

I have heated O2's. I only replaced the left bank O2 since it was the only one which pulled a code. The right bank O2 didn't have a code so I left it, since anything on the passenger side is hard to get to I didn't feel like messing with it at the time if it didn't pull a code, I didn't bother to take it off to clean or anything. But, like I said I was told it could be faulty and a code may not show up. Was also told that even if the symptoms didnt occur got better that the O2 still may not be the cause of the closed loop problem, even though it seems that it is. So now I'm just wondering what else could cause these symptoms during closed loop operation. I will also get to checking fuel pressure soon just to go ahead and get that out of the way.

**EDIT**
Well car sat in driveway for an hour or so, went out to swap positions in driveway. The car had terrible fluctuating idle rpm's ranging from 700 to 1700 rpm's. This is the first time since disconnecting the O2 for Open Loop it has done this since the adjustments. Obviously still have kinks to work out.

 

yes when fouled or failing the 02's can give false readings that are within the proper range so no code will come up.