Hello everyone my name is Tyler and this is my 1992 k1500 blazer sport with the 350 TBI . She was my father's truck before me and I've been trying to restore her to her former glory after sitting for 7 years. So my issue is my idle. When it's cold it idles high around almost 1100ish rpm until it warms up and it will sit at 750 for the most part but sometimes it surges for a few minutes after warming up and levels back out. It will also die sometimes putting in to gear but always starts right back up no problem. When the truck is in drive at a light it will sometimes idle low after warming up between 5 to 600 rpm and it never dies when I keep it in drive but when I go to put it in park it will. But at the end of the day I'm not sure if it's my iac valve or a vacuum leak. Just to get a complete picture I've replaced the motor and transmission. Every sensor and connector on the entire truck. New fuel tank, pump and fuel filter. I've replaced all the ground straps to my knowledge could have missed one I'm not sure. I've replaced the brake booster and master cylinder. All the ignition parts are brand new. The entire TBI is rebuilt with new parts and gaskets. I'm at my wits end I'm not a certified mechanic and I've spent so much money throwing parts at it or in and out of shops who can't resolve the issue. Bottom line I need help from my fellow blazer peeps please help. Thanks everyone have a blessed night

 

Welcome to the forum! Pretty nice looking truck!

Does the truck still have the factory EGR system? These can sometimes cause an issue with idle quality which can lead to stalling when there is an abrupt change in load on the engine (putting it into or out of gear for example).

I would not rule out vacuum leaks either, but a vacuum leak typically does not cause the engine to stall when putting the transmission in or out of gear.

When the throttle body was rebuilt, was the throttle shaft checked for excessive play where it goes through the outer walls of the throttle body itself? It is somewhat common for vacuum leaks at this location, but as I said above I wouldn't expect a vacuum leak to result in the symptoms you are experiencing.

 

Yes the EGR valve was replaced. I did recently take the throttle body off, cleaned up the gasket surface and replaced the gaskets but I didn't think to check if their was any play in the throttle body itself. I did add a 1/4 spacer kit which came with a new spring for the fuel regulator. I've tested the fuel pressure and it was reading 12-13 psi. Tested vacuum and it was around 19 inches at idle. I tried doing a smoke test but I'm not sure if I did it correctly I had a hard time covering the throttle body. not sure if some of the parts I replaced are working correctly. Not sure if if the shop timed it correctly. But today it actually got a little worse and popped a obd1 code 32 and now it won't idle below 1000+ rpm.