I have a 88 camaro. Came factory with 305 TBI. Was told when I bought it that the 305 was pulled and a 350 was dropped in. Found GM5.7 stamped into the back of block. The swapper used the original TBI. I was worried about the engine running lean. Tuned it up and checked the old plugs. No signs of a lean mixture. Plugs actually looked good. Anyway the problem I am having is when you start the engine when cold it surges. Revs up to about 1500 rpm and then droppes below 500 rpm. revs and falls, revs and falls for several minutes before calming down and idling at about 800 rpm or so. The problem I am conserned with is after driving the idle jumps to 1800 rpm. The idle will not fall below that until you shut it off and let it cool down. Any suggestions would be greatly appreciated.

This is my first thread or post. Haven't even replyed before. Hope I did it right.

 

Remove the tbi unit & clean all the passages, replace the base gasket, they sometimes go bad.

 

Thanks for the advise. I will have to give that a try.

 

I would do a vacuum leak test, if you got a leak 9 outa 10 times it will show it, the tbi gaskets are a great start as well

 

5.0L injectors need to be changed to 5.7L injectors also. But it does sound like a vacuum leak