I have posted a few times on this "project" Replaced EGR and encountered a few problems after I put the TPI back together. I am getting a strong vacum leak in the area of the plenum to top runners and the car idles high as hell. I have taken it apart 3 times to check for misallignment, bent gaskets, or debris at the seal, every time I have the same result. I bought the high quality gaskets from GM (all the techs recomended them)

someone told me that I can use RTV sealant on there to help eleminate the leak. Is this true?, because I am at the end of my rope.

I cant even begin to mess with the idle untill I solve this vacum problem. any and all suggestions welcome.

Bombero

 

Sorry, the car is a 1989 IROC-Z Convertible 305 TPI 5-Speed

 

sorry again, Im just frustrated, Yes I did check for vacum leaks, ALL the lines are correct and intact, it it infact leaking at the plenum and runnerz.............

Bombero

 

If it's the plenum to top runners the next thing I would check is for warped runner flanges. I've always used Fel-Pro gaskets for damn-near everything and never had one leak in any application. Also check the power brake vacuum hose fitting, FPR and MAP sensor vacuum fittings. May want to pull those and put some teflon thread sealer on them just to be sure they aren't the problem.

Another thing I just thought of is maybe it's possible to have the runners switched, as in the passenger side runner and driver side runner switched? I'm sure you probably didn't do that, I'm just brainstorming right now and I doubt it's even possible. Hope this helps.

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1990 IROC 350
Mods: Too busy trying to make it run right to mod it.
Airfoil, Dynomax cat-back, MSD coil, 180 t-stat, Bald Eagle tires,
Hypertech fan switch, Accel 23# injectors, Holley AFPR, ported plenum,
Ported Daytona Yellow stock base, Moroso valve covers, other stuff,
Ruger P95DC, hot wife, new oil filter, thick rubber floormats, no cats.
18.0 @ 85MPH since I'm one big-a$$ MF
"It's better to have and not need than to need and not have."

 

hello, get a can of carb cleaner and with the motor running, spray around the motor. when you find the vacuum leak, the idle will increase. just spray the whole intake side. may take a couple of passes to find a small leak. best of luck, tom

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86 iroc 305tpi auto. mild cam

 

Not sure who made these gaskets, but they are Not cheesy, maybe felpro maybe not but, quality for sure. Brake booster hose is on and looks good., I thought also that I might have switched the runners too. But they are on correct, ( the EGR exhaust tube goes on the pass side)almost cant get them wrong, LOL (almost)......well what I want to know is, can I use the RTV Sealant on the whole set-up just to fixx the problem, even if it is a warpped flange (which was not warpped when I took it off).

TYhanx........ Bombero

 

I don't see why not, just don't go too liberal and obstruct the runner passages. Use a good high temp RTV.

 

Another thing to check (got bit by this myself) is to look for misalignment with the runners to the base.

 

You also might have the gaskets switched. Although the gaskets look pretty much the same from one side to another, they're not. When I did this (a couple times!!) it would leak. Take off the runners and look at the gaskets to make sure they're on the correct side.

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92 Z28 5.7
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Trick Flow 23° heads, Comp Cams XR270HR-10 cam, Accel intake base + ported TPI,
TES headers, Flowmaster catback, MSD ignition, #24 SVO injectors, 1LE aluminum driveshaft.

Click here to see pics of my car !

 

It is very easy to switch gaskets and it will produce a nasty leak. Using the Silicone you speak of is fine but you have a bigger problem than that because the sealant shouldn't be necessary.

Double check your intake manifold... especially the 4 center bolts for 40# torque, and if you have a cold start valve make sure you didn't bend the flange on install. With all the potential leak spots: injectors, upper/lower runners, cold start, TB, hoses, etc. it is a bit hard to "pinpoint" exactly where a leak is coming from.

Also are you throwing a code 44?

 

Thanx to everyone, I found my leak, it was on the PCV vac line right at the point where it connects to the intake mainifold. I only found it after the 4th time r&r the plenum and runners. What a pain.

P.S. I did use the RTV sealant only because I was 1/2 way into it when I found the Vac line .

I still have the high idle though, I did replace my TPS & IAC about 6 months ago for the same reason, could they have gone bad again?