Rough idle when in gear

I have a 1990 240sx with an automatic transmission. When it is in nuetral or park it idles fine, but when I have it in gear and stopped at a red light or something it idles between 500 and 650 rpm and shakes a lot. I replaced the air filter plugs and wires but it didn't do any good. The transmission slips a lot (and has since I bought the car 13K miles ago), the mufflers are rotted out with very large holes and the O2 sensor probably hasn't been replaced in a long time. Could any of those things be the problem, or is there anything else it could be? Thanks in advance for your help,
Dan

I have a 1990 240sx with an automatic transmission. When it is in nuetral or park it idles fine, but when I have it in gear and stopped at a red light or something it idles between 500 and 650 rpm and shakes a lot. I replaced the air filter plugs and wires but it didn't do any good. The transmission slips a lot (and has since I bought the car 13K miles ago), the mufflers are rotted out with very large holes and the O2 sensor probably hasn't been replaced in a long time. Could any of those things be the problem, or is there anything else it could be? Thanks in advance for your help,
Dan

This is a very common symptom of a variety of problems... the shaking can be your timing chain rubbing if your guides have worn off... It could just be carbon buildup too.. rev your engine in park or neutral and see how it responds (does the needle lag at any point?) It could be a clogged AICV... theres a sticky at the NICO forums on how to clean/remove that. Damn, it might even be your ground wires/connections. Be careful when checking these things or you might end up worse than you began.

My girlfriend had this exact problem with her Toyota Celica. She would put the car in park it would idel fine but when she had it in drive and would brake it would shake, and sometimes stall. So we replaced the fuel pump, and fuel lines, then used carberator or injector cleaner. That seemed to fix the problem almost completely.

today i noticed a little fuel leaking from one of my injectors, so i bought the little kits with the o-ring, and other rubber parts hoping it would fix the shaking/ low idle problem. but after messing with the injectors it seems worse. now, along witht he low idle in gear, it surges and drops off when in park. i'm totally cheap (i bought the car for $200 and have put about another $1000 into it in a year) and HATE to take my vehicles to a mechanic, but this problem is just bugging the crap out of me. i'm afraid if i take it to a mechanic they'll quote me an outrageous price to fix all sorts of unnecesary things. is there a way i can check to find out if the injectors are working properly? someone said something about an AICV. what it that and where can i find out more about ?

Thanks again,
Dan

hope nobody gets pissed off im posting another forum's link but all the info is there...

http://www.nissaninfiniticlub.net/forums/showthread.php?threadid=26150

Good luck!