I replaced the leaking intake manifold gaskets on my 99 Jimmy 4.3 4x4 yesterday. Its got 100,000 miles on it. Everything went fine, it all went together better then I thought it would. So I drove it about 40 miles, and the check engine light came on. So I stopped by a repair garage and he put the code reader on it and it said something about "lean mixture condition on banks 1 and 2". The mechanic cleared the light and sprayed some aerosal stuff around some hoses, looking for air leaks but found none. I drove another 60 miles and the light came on again reading the same condition. Any ideas on what might be going on with this? Everything else seems fine, the Jimmy still runs like new, and the temperature gauge reads normal. Thanks

Sounds like a vacuum leak. The mechanic was spraying carb cleaner around the vacuum lines and connections. A change in idle when spraying an area is a sign of a vacuum leak.

I see. Also, if this turns into one of those things that takes forever to figure out, what is the best code reader that i can buy? One that will turn the check engine light off, so I can moniter the situation myself as i attempt to find the problem? Thanks

Matco makes a nice little code reader for really cheap, highly recommend it!

MC200 MICRO CODE READER | Matco Tools

As for your problem, are you sure you have the clamps tight on the intake tube? Even myself I've caught myself overlooking this at the end of a job in a bit of a rush to get it finished. brake clean is a good chemical to spray and listen for the idle to change. Just make sure you don't have any ignition leaks or you could be in for a rude awakening! (been there done that )

Haha, yeah, sparks and flammables dont mix too good. I'm going to reinspect everything tomorrow morning. I know for sure I got one little air line thats dryed and cracked, but I dont think its leaking, but I'm going to replace it anyway.
If I remember right, the 1990 S10 I used to have, you would just put a jumper across 2 terminals at the code port under the dash to clear the check engine light, but I doudt if my 99 Jimmy works like that, am I right?
Will that Matco turn off the check engine light? thanks

theres alot cheaper ones if you just want to read and clear codes look on ebay or amazon. or if you have android phone you can use a cheap bluetooth to obd2 adapter and torque.

when i did my manifold i had the same thing there was a small tube that was for the heater cutoff or something

it was kinda lost down in the side of the enigne when i was swinging stuff over

I found it just now.........just like u guys said, I left one air line laying off to the side, hidden amongst a bunch of other lines........I opened my hood, ready for a long, hopeless inspection, and the 1st line I grabbed, came up just hanging there !! Engine'* been running now for 10 minutes and the light is still on, I'm gonna run down to the repair shop and have them turn it off. Good way to start the day. Thanks very much

Anytime you make a repair that involves the check engine light, it usually takes a few drive cycles for it to clear out. With some things, it can take as many as 50 cold starts for the PCM to do the test and see it not fail those 50 times.

I had the same problem with that 1 vac line when I did my gaskets last year.

Yes, and you know, all the problems people have had with the dexcool red antifreeze turning to brown goop..........my manifold surfaces were perfectly clean (except for the old gasket material)........and i believe i know why.......ever since the Jimmy was new, i drained the radiator 2 or 3 times a year, and refilled with 50% dexcool and 50% DISTILLED water from the grocery store (always drain when motor is cold,never drain with hot motor).....i really think the combination of draining often and using distilled water instead of tap water turned out to be a good idea