check ignition wires.

[zeeman]

I believe so. I know I've seen posts about iac counts. Would that also effect it running down the road?


Man this car is kicking my ass.

[zeeman]

Also, is there a list of sensor values somewhere? I can hook up to my laptop and watch the show but I have very little idea what should read what.

[zeeman]

Does the LT1 have an idle air control valve?

Ding ding ding ding ding!!! We have a winner! ( preliminary reports indicate)
Scanned it this morning, iac was over 100. Hit the "reset iac" button (thank you gary doug) and everything is now right with the universe.
Now if the roads would just dry up I could get in a test run.

[hoogiesngrinderz]

I'd pull that IAC and really clean it, might be able to save it. Probably best to replace it with a AC Delco unit. When I first got my IROC it did the idle search, but never caused a lean miss/knock. That was a stock (peanut cam) 305 though...

If I remember right, didn't people have issues with the IAC pins pushing back? I could be thinking of another connector...not a lot of hands on time with LT1

[zeeman]

This is my first lt1, I don't know a lot but I'm learning faster than I would like. lol

I am going to borrow one from a bud before I buy one. Just to make sure. It started doing it again this afternoon. So I am going to have to do something. Genuine GM would be great, but we will have to see about price and availability.

[JoeliusZ28]

Hope that solves it for you. Theres some light at the end of the tunnel though, while these engines are finicky there are only so many parts that can go bad. Ultimately the engines are great when all the misc BS around them are working properly.

[zeeman]

me to but I am not so sure anymore.


I drove it to work and it acted up on me on the way in. same stuff. drove home, it was a bit better behaved. Scanned it when I got home. dtc 36

0

Distributor ignition system (faulty high resolution pulse or extra low resolution pulse detected) optispark? 2nd thing , the target for the iac is 17, but I see it go below that, 14 at times, and also higher. Im going to put a iac in it tomorrow. my biggest concern right now is the dtc 36. first time ive seen it. cause for alarm? it is a brand new msd unit

[Lucky SOB]

Yeah the IAC on my old 4.3 S10 gave me fits for a while. I hope it's as easy as replacing it for you!

I temporarily fixed mine by scrubbing it with carb/choke cleaner, but eventually replaced it.

[zeeman]

Installed a new iac. new target # is like 15, it varies a bit. At idle Im seeing 10 - 15. no more 80's. with the lights on the idle is now staying high enough to keep charging the bat. thats a nice benefit of a properly functioning iac system. Nice even idle, lower than I prefer, 575 in gear, but its even. No more dtc 36 which is nice, Ill just keep an eye on it, scan it from time to time.
I dont want to use the "f" word just yet. seems like every time I do.....it isnt so for now Ill just say I am happily hopeful.
Thanks for the support fella's it is much appreciated.

[Lucky SOB]

[zeeman]

Well lets just say I knew better.
I drove it around saturday after putting the new I.A.C. in it. Took it to Ma and Pa's yesterday for Easter Dinner, Drove it to work today, was just starting to relax and enjoy it. I came to a stop light, and it surged forward a bit..... "What the eff was that?" Look at the tach. ...see it twitch... S.O.B! Sure enough a few seconds later I am at 1500 rpms in drive. So I baby it home and go get the lap top and plug in. The I.A.C. # are all over the map 100 and better all the way down to 13. So I have another one on the way.
Spark knocking, lean running p.o.s.! ok I feel a little better.

[zeeman]

On a positive note. While talking with one of the mechanics at work, who is a fellow Z-28 owner. I was telling him all what I have done to the car since I bought it. I described an annoying shake/vibration/miss from the engine since putting it back together. I was picking his brain about the amount of preload used on the lifters. he felt 3/4 turn was to much on a used cam with new lifters. I had read today on a couple different forums that 1/4 turn, and a couple guys even went as far as to use 1/8th of a turn to set their preload. So, when I got it home, uneven idle and all, I removed one valve cover at a time and reset all of them to 1/4 turn past zero lash. While running. While the engine scaled up and down and up and down, throwing oil all over the place. I even managed to set the passengers side on fire. Oil is pretty flammable apparently... Who Knew????....
Any way the outcome of this is a much smoother running engine...Even with a bad I.A.C So hopefully I will replace it tomorrow and be able to put the rest of this nonsense behind me.

But I still wont use the "F" word....Well....not that one anyways....

[hoogiesngrinderz]

Wish I could help you, Joe. I have clips to deflect oil while the valve covers are off.

I have NEVER gone 3/4 turn after zero lash. Many variables, but 1/2 turn works well for me.

[JoeliusZ28]

Every engine is different. Mine is set to 1/3 turn. I noticed binding around 2/3 turn for most of my lifters, IMO you want it right in the middle between 0 lash and bottomed out. Too little lash is usually noisey. but binding valvetrain will definitely affect your idle. (i did engine off method, its easy to tell how far past zero is bottomed out that way). If its running good and quiet though, leave it be.

[zeeman]

When the car would idle normally. I would loosen a rocker and the engine would pick up. Then When I would tighten it after zero lash it would slow down/ stutter, then correct itself somewhat. So I knew something wasn't right. I am sure after I get the idle/iac/control module situation remedied, I will go through the valve adjustment again. With this iac problem, when the rpms go up it throws oil everwhere, especially on the headers. That was a bit of panic I didn't need.
A bud has an icm for me to borrow, and I am putting a new iac on it tonight. I read that my iac at idle should read around 30 -35? my last one was 17. Should I adjust the tb to hit that 30 - 35#? I know the tps is involved too. It needs to read .65 volts when the iac reads 30 - 35, and the idle is
correct. Or am I missing something?
My engine is stock, so a stock tps should work at the factory setting. So it would just be a matter of setting the tb blade opening so the iac count would be correct then right?