i just did an s4 to s4 motor swap same year everything is good both naturally aspriated, but the one i put in was suspossed to work better due to that it has 80k less miles and driving by an old lady, so i don't know why but when i start it, it will try to idle but struggle then die shortly after probably 2-5 seconds into idle, i don't know whats the problem. or what could be causing it

 

vaccum leak. the car runs on defautl map for a few seconds when it starts, then after that, it takes over the readign from the AFM, etc. chances are, the leak is big that the afm shuts and you hit fuel cut. check for leaks on the intake area

 

thanks your ballin

 

i know i am... now if only emma would think that so i could marry her

 

lol i see, so exactly how did you come to know all of this? cause i'v been browsing the threads and you know alot of s**t for reals.

 

there just isnt much that fits your symtoms, if you **** with the afm when you car is running, i bet you could get a spot where it would run at 1.7k or so.. with a bad, messed up afm, or a leak, it would start but usually die a bit after. the fact that it even starts at all elminates a possible motor problem... the fact that these cars have 37 vaccum lines doesnt help either! maybe you forgot an injector grommet?

 

uhh i don't want to sound like a retard but whats an injector grommet?

 

that little rubber oring that the injector sits on

 

Injector grommet is a rubber (or, if you have 100k miles, PLASTIC) ring that goes at the base of the injector and then gets pushed into the block/manifold. If you are missing one it'll create a gigantic vacuum leak. The plus side is that your fuel would be well atomized. Hehe.

If you didn't replace them when you did the swap, you probably should (along with the injector o-rings).. Unless you did a basic swap and didn't take anything off the block; Then you are probably okay.

Make sure your AFM is plugged in all the way or at all.. If I leave mine unplugged, it starts, rev's to about 1800-2k then dies. Similar but not the same.. Mine's an S5.. Not sure what the S4's do.. I only had my 86 for a couple months.

 

fuel lines are reversed dummy

and just because one of these engines was driven by an old lady does not mean it is in prime shape, it is not a piston motor.. these motors more closely resemble a lamborghini V12 that needs to breathe to keep from choking on itself. long periods of low RPM use are considered abuse with these engines as low RPMs accumulate more carbon deposits than the engine will accumulate at higher RPMs such as near redline.. i redline my car once a day if not more when i can, even on my 2 mile commute to work.