fixture

hello all,

I have searched a bunch on the forums and I haven't found the issue that I have. My knock sensors were bad so I replaced them along with the intake manifold gasket (Fel-Pro). I cleaned the IAC, and the throttle body. New sparkplugs, 4 new 02 sensors and PCV valve. When I start the car cold the idle bounces from 600 to 400. About a minute or 2 later the idle is steady. Is there a cold start sensor or something else that I need to check? Also when I drive it, I can kind of hear an air sound from the drivers side. Kind of near the brake booster area, but cant be for certain. The service engine light is on, but no error codes have come up yet. I have let the truck go thru a couple heat cycles and have re-torqued the intake to 88 in lbs.

I have read that its best to use the AC Delco factory intake gasket, but I had them side by side with the Fel-Pro and they looked identical.

Any thoughts?

Thank for any help.

Jonathan

73shark

Welcome to the forum.
Check the vacuum at idle while it's in the open loop mode and cold to see if the vacuum changes with the idle speed changes.

SBchevyfan

With the engine cold, start the engine and while it is running, spray carb cleaner around the edges of the intake manifold. If the new gasket didn't seal correctly there will be a change in the rpm.

jawsmon

You can also use WD40 or starter fluid to look for a vacumn leak.

fixture

Here is a video of my issue. List of codes I got without the check engine light on, these were not cleared after I put on the new knock sensors, so those codes are still showing. It wont stay started unless I give it gas, then a minute in I can take my foot off and this happens. I will head out today to get some starting fluid or carb cleaner to check for leaks when cold.

The sparkplugs I used were Bosch 4509 Platinum Ir Iridium Fusion Spark Plug, which per the manual are ok to use.