High idle...vacuum leak?
Thread Starter
Teching In
Joined: May 2017
Posts: 12
Likes: 0
From: Park hill, ok
High idle...vacuum leak? Hey guys just got done doing a cam swap, and some head work on my 95 z28 with an lt1. When I bought the car it had a high idle after it warmed up, and still does even after the rebuild. When pulling the injectors before the rebuild I noticed a few O rings were pretty worn and damaged. I couldn't track down a rebuild kit at the local parts stores, so i did the stupid thing and put them right back in after i finished her up. When it starts it idles excellent for about a min or 2, the their she goes 1500+ rpms. I noticed when spraying carb cleaner around them the idle did fluctuate up and down (mainly down) when I sprayed around the injector bases. Are the damaged o rings the culprit here or am I missing something. I did order new injectors cause these are old, plus it's getting the spray to it so uprising injectors a little. Thanks for the help in advance!
Staging Lane
Joined: Sep 2012
Posts: 85
Likes: 0
From: Virginia Beach, VA
It's more likely that your vacuum leak is not related to the injector o-rings, but to the sealing gasket between the intake manifold and the heads. That would account for the idle variation when you sprayed carb cleaner on the injectors. Also don't rule out a leak at the manifold vacuum hose connector to the power brake booster. That's another common source of leaks.
Thread Starter
Teching In
Joined: May 2017
Posts: 12
Likes: 0
From: Park hill, ok
Hey guys thanks for the advice, I did put a brand new gasket set on the motor when I rebuilt it, i realize its possible for gaskets to maybe be bad when their new. I did recheck the torque on the manifold bolts they are good as well. Ill check the brake booster hose, and other rubber hoses as well. I took a closer look at the injector o rings, and their are a few that are pinched/crimped up out of the injector seats on the manifold. So still not for sure.
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
IDK if your used FI seals are the source of the leak....but IMHO on a new motor with your description that some don't look like they are sitting right and or cracked...appears to be a vac leak somewhere.....I would replace them
beyond that confirm all vac lines are hooked up correctly and in good shape
I had my TB gasket on wonky and that is where it had a bad vac leak when I put the motor back in. My mistake and didn't find it initially
beyond that confirm all vac lines are hooked up correctly and in good shape
I had my TB gasket on wonky and that is where it had a bad vac leak when I put the motor back in. My mistake and didn't find it initially
Thread Starter
Teching In
Joined: May 2017
Posts: 12
Likes: 0
From: Park hill, ok
Ya ****** I agree on replacing them, as stated in and earlier comment I did order new bosch 30lb injectors so that will take care of the O ring problem. I did pull the vacuum hose from the brake booster and inspect it. It actually looked fairly new. Put it all back in and it actually acted a little better on idling then before. So maybe it's a combination of multiple leaks.
Trending Topics
Thread Starter
Teching In
Joined: May 2017
Posts: 12
Likes: 0
From: Park hill, ok
No it will be though. Im getting a tune from Solomon wednesday. I had another problem occur today. It's hesitating and sputtering while accelerating, easy or hard. Acts like a melted wire in a way, but it does clear up sometimes also so Idk. It's probably been a long time since this car probably hasnt had a good tune up, in God knows how long (fuel filter, can, rotor, wires, etc.). Hot new plugs with rebuild though. It's either that or maybe the opti?
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
[QUOTE=Sstanley89;19657508]Hey guys just got done doing a cam swap, and some head work on my 95 z28 with an lt1. QUOTE]
Now that the heads have been decked the fitment of the intake manifold may be off not allowing a good seal. You would need to see/measure by dry setting the manifold to determine if there is any front/rear china wall gap or runners/head gap. Some decking of the appropriate surface of the intake manifold and/or elongating the holes on the intake may be necessary
smoke test would quickly find this type of leak quickly to rule in/out a intake manifold leak
use FelPro "printle" seal (blue stripe) intake gaskets and Permatex Black "ultra" RTV on the china walls. Let motor sit over night for RTV to cure before starting motor
Now that the heads have been decked the fitment of the intake manifold may be off not allowing a good seal. You would need to see/measure by dry setting the manifold to determine if there is any front/rear china wall gap or runners/head gap. Some decking of the appropriate surface of the intake manifold and/or elongating the holes on the intake may be necessary
smoke test would quickly find this type of leak quickly to rule in/out a intake manifold leak
use FelPro "printle" seal (blue stripe) intake gaskets and Permatex Black "ultra" RTV on the china walls. Let motor sit over night for RTV to cure before starting motor
No it will be though. Im getting a tune from Solomon wednesday. I had another problem occur today. It's hesitating and sputtering while accelerating, easy or hard. Acts like a melted wire in a way, but it does clear up sometimes also so Idk. It's probably been a long time since this car probably hasnt had a good tune up, in God knows how long (fuel filter, can, rotor, wires, etc.). Hot new plugs with rebuild though. It's either that or maybe the opti?
What cam did you go with? Your PCM may be pissed. Check for burnt plug wires anyway. Get a volt meter on your TPS and see where it's at. Either do a search here or buy yourself a Haynes manual which will tell you how to do it. There's also a technique on how to reset your IAC on this page:
www.shbox.com
www.shbox.com
Thread Starter
Teching In
Joined: May 2017
Posts: 12
Likes: 0
From: Park hill, ok
Lt4 hotcam. Got it for dirt cheap brand new in the package. I bought a chilton manual when I first bought the car a month ago. So I'll deffinently check into that. I planned on having my tune sent to me when I got my injectors. To see if that clears it up at all. Cause I know with me adjusting the idle on eehack it idle right, but the moment I disconnect the cable. It shoots right back up.
What size shot?
"All of it." is not a valid answer.
Years ago there were many who would run 75 to 150 wet shot on bone stock motors. Larger injectors weren't necessary. Just make sure you know what your O2's are doing when running N2O. Too many would get greedy and blow out a ringland or two because of detonation.
"All of it." is not a valid answer.
Years ago there were many who would run 75 to 150 wet shot on bone stock motors. Larger injectors weren't necessary. Just make sure you know what your O2's are doing when running N2O. Too many would get greedy and blow out a ringland or two because of detonation.