So my 2002 t/a won't idle in gear its a a4 I put it into drive and the rpm goes to 1000rpm and drop to under 800 then it will die I have to brake and gas coming up to light but if its in park idles fine just put a new tps and cleaned maf and iac

 

Your iac valve could be bad or check for a vacuum leak

 

K Imma check for a vacuum leak first

 

when did it start? what mods or repairs have you done lately? it could be lots of things from iat, tb, tps, maf..may be plus or coils and as stated above check vacuum leaks but generally vacuum leaks would higher the idle rather than lowering it...i would also check fuel pressure.

 

it started after i rebuilt my ls1 motor and all i have is a cheatr cam and 4000 stall i replaced the tps just yesterday i would of thought it would throw a check engine light but nothing but when i start it some times the rpm goes up and dwn give it a little gas and goes away but soon as i put it in drive it goes up and down and then dies

 

If you can, check your idle air motor for "counts". They should be between 40-60, or so.
As an example, mine is stuck at zero (o idle counts). This means that the idle air motor is not adding any more air. Adding air through the idle air motor helps keep the engine from dying. So, like you, I have a problem that I have not yet located.
I found a cheapie idle air motor on ebay, which I swapped in. It didn't solve the problem. Nor, have I been able to locate any vacuum leaks.
Good luck!

 

I fought this a while back with a new TB. The "cheapie" IAC I replaced mine with, just as insurance, actually had the wrong sized nipple.

Something else to check for is to make sure the O-ring is seated on the IAC before install.

A can of MAF cleaner or cheap can of starter fluid is great at spraying around and checking for vacuum leaks.

 

To help check for vacuum leaks...

 

Im with everyone else that it will be best to check for the vacuum leak and see what your IAC is doing. If you can get ahold of a scanner of some kind that will read the IAC counts that would be easiest.

 

K haven't got to it yet imma do it tomorrow and let y'all no and I don't have a scanner that reads iac counts if I do what a good iac count

 

Try this worked for me. No.6 post: https://ls1tech.com/forums/pcm-diagn...-idle-ls1.html My idle was going crazy when I swapped to a different type of oxygen sensor done this reset all is well.Need a scanner for setting tps percentage.