hey guys I really need some help here. I have a 89 rs that I swapped in a older model 350(70S maybe early 80S) It is mildly rebuilt 355 but then I added an 86 tpi. Now it surges at idle and will barely run when warm. I know it has a vacuum leak but i don't know where to look for it. It makes no obvious hissing noises and I don't think I left off any lines. I sprayed wd-40 around the throttle body/phlenum and where the runners bolt to the phlenum and where they bolt to the manifold. I did make a egr blockoff plate from .500 aluminum and I checked around there as well. Can you guys give me any suggestions please.

 

I found some of my leaks around the Injectors. I guess I didnt tighten the rail down enough. I also forgot about the hose under the TB. You could also have an internal leak. Check your vacume. spray some carb cleaer in your oil fill hole while running and see if the idle gets rough.

 

You also wanna check near the coil. There's a few lines that run there that hook up to the timing advance unit.

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85 2.8L Sport Coupe 5-speed.
Mods: Hpertech chip and powerstat, MSD 6A-L, Crane fireball coil, Accel Cap and Rotor, Dynomax hi-flow cat and catback system with a dynomax magnum race bullet muffler on the i-pipe, K&N filterchargers, Gutted Air Boxes, 8mm Wires, Eibach Sportlines and Tokiko springs/shocks setup, Global west sub frames, Suspension techniqs front and rear sway bars, and good ole 88 IROC wheels with Kumo Ecstas on em!
"It's not the ricers, it's those damn V8's!"

Wins: 2000 V6 Accord, 69 302 Mustang, 2000 Auto VR6 Jetta, 89 Toyota MR2, 90 Civic Si, 76 350 Camaro, 2000 3.8 5-speed Camaro, ~68 Chevelle 350, 92 CRX Si, 94 MR2 non-turbo.

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You could try listening to all the joints on your TPI to see if everything is tighetened up by using a small section of hose that you hold against your ear. It will help pinpoint the leak much better if you can hear it through the hose.

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1991 Z28 5.7 TPI

ZZ4 heads, ZZ4 cam, Harland Sharp roller rockers, Accel base, SLP siamesed runners, 52MM SLP Throttle Body, Hooker Headers, Flowmaster catback, MSD6A ignition, Home made ramair system, 2500 stall, bullet proof 700R4, aluminum driveshaft...

Soon to be installed. WC T5 !

 

thanks for your help guys. I appreciate it. Especially the tip about the hose to listen for noise I remember that from auto shop in high school now. I will check those places this weekend but I was wondering what was meant by spraying carb cleaner in the oil cap? I assume you mean the cap on the valve cover. Can there be a vacuum leak there?