rough idle problem

I have a 1990 mustang gt and my problem is that every time I step on the gas accelarates rough it rattles and smeels funny please help!  

Wow! I owned a 90 LX for 10 yrs and put 100,000 miles on it. I never had such problems. You don't mention how many miles are on the car or what type of maintenance schedule you subscribe to. It sounds like the car REALLY needs a good tune-up. New spark plugs, wires, dist cap and air filter would a great place to start. Is the funny smell gas or does it smell like rotten eggs? Rotten eggs would mean your cats are shot. Replace them or put in a X-pipe.  

I am having a similar problem with my 91 LX, it runs rough, and stumbles all over itself until I get up around 3500-4000 RPM, I replaced the basics...plugs, wires, cap, and rotor but no change, so I let it cool down, I started it up and let it idle for a couple min. shut it off and started pulling plugs, what I found was #2 was fuel soaked, so I cleaned it up and tried again, it was fine for a couple min. and started missing again. I decided I had a fuel injector problem so I replaced the fuel injector, but again "NO JOY". While it is running you can go to the back, and the exhaust is so rich it will make your eyes water, I know this probably doesnt help much, but if it is the same problem you are having my hope is that someone will read this and help both of us. I will keep trying.
Mark  

I WOULD CHECK OUT THE VOLTAGE COMING FROM THE ALTERNATOR. ALOT OF TIMES ESPECIALLY IF YOU HAVE MODS,SUCH AS CAM OR PULLIES WHEN THE ALTERNATOR IS STARTING TO GO IT WONT SEND PROPER VOLTAGE BACK TO THE COMPUTER, THERE FOR IT'S NOT GETTING THE PROPER AMOUNT VOLTAGE THROUGH OUT THE SYSTEM THIS HAPPENED TO MY 87 THIS PAST SUMMER DROVE ME CRAZY. THE CAR WOULD RUN OK AND AS SOON AS I GOT ON THE THROTTLE THE CAR BOGGED ALL OVER THE PLACE


PS WHAT KIND OF MODS TO YOU GUYS HAVE  

I was having a similar issue with my 93 LX bogging and stumbling at lower RPMs and I had a sizable vacuum leak. Grab a vacuum gauge and take a measurement on the tree above the brake booster on the firewall. Should have around 16 in/hg. If you don't have a gauge, pick one up at Sears for about 25 bucks. 18-22 is what they say you should have but on an older engine you'd be lucky to see 18. Check the plastic lines, they become brittle and snap like glass. Also check the line from the evap canister, the rubber rots away from the gas fumes.  

I would also check the O2 sensor. Does the car smoke? If it smokes real white it is a blowed head gasket. If if smokes black it is to much gas. If it smokes kinda blue tint it is oil. Yes check the cats and any vaccume leaks.  

Well I did some more troubleshooting, and my problem is that #1 injector lead has a constant 14 VDC going to it, all the others open and close, but #1 stays at 14 volts, it does not pulse like the rest, in my earlier post I wrote #2, but it is #1. All I can think of is that there is a short in the injector wire for #1....what a pain.
Mark  

CUT OFF THE CATS!!!
I HATE CATS!FUR OR NO FUR IT DOSEN'T MATTER