1fast97gsx

I would really appreciate some help on this as it's starting to drive me crazy. This is on my daily driver ... 1995 mustang gt. The car idles great and runs great under wot and even at 50% throttle. If I take off off of a stop light at a slow speed the car feels like it has a misfire/stumble. It's very hard to notice and most people wouldn't even know it was happening when they are in the car but I know it's there and it shouldn't be so it bothers me. Even if I'm going say 20 mph and want to accelerate to 40 and accelerate slowly I feel the miss ... if I push the gas down just a bit more it clears up. I put in brand new plugs, wires and a fuel filter. I checked the timing and it's set at 10 degrees as per manual. I first considered a slow reading O2 sensor to be the problem, but it doesn't stumble if I take off a little harder keeping the car in closed loop so that rules that out. Plugs, wires and fuel filter didn't do anything but up my gas mileage. Timing is good. I can't physically hear any vacuum leaks when the engine is idleing, so I'm not sure where to go from here. Just for testing purposes ( assuming a bad egr is causing my problem ) I unhooked the vacuum hose going to it and blocked both the hose and the valve. No change. I'm assuming it has to be a pcv valve at this point?

Chopper

Check for low fuel pressure,clogged or dirty injectors,and a buildup of carbon behind the throttle blade.

Vmak812

yea injection would be my first guess, or something in your gas tank/lines

something similar happened to my old car, and it turned out to be related to the spark plugs, but not the actual plugs so cleaning didnt them didnt make much difference

1fast97gsx

Thanks for the suggestions. I'm going to replace the pcv today and get some injector cleaner and run that through. Any advice on which stuff works best?

Also if it was a low fuel pressure problem wouldn't I have a miss at wot and higher rpms rather than at low rpms and almost no throttle?

ackuric

similar issue here bro, lemme know if the pcv helps at all.

1fast97gsx

old pcv was fine. It has to be a vacuum leak. Although I can't hear one or find it the smaller sized hose that comes out underneath the intake manifold on the back side looks very old and torn up. That has to be the problem. I just can't get my arm in there to pull it off and slip a new one on. Any tips?

1fast97gsx

I got the hose off and replaced it. Still no change. I notice the car also sort of stumbles if I give it a soft rev in neutral.

1fast97gsx

Also I just tried a soft brake torque to 1500 or so and it misses the whole time. It seems like the car wants to miss at anything under 2000 rpms. The car also has a slight vibration at idle. Not sure if that's a miss or just normal. Tach needle is steady.

Chopper

It sounds like a worn out injector.After they wear out they don't atomize the fuel like they used to.When the rpm's get higher the airflow helps to beat the larger fuel droplets into submission.
You can remove the wires from the injectors one at a time like a spark plug test to find a cylinder that might be at fault.This test might be inconclusive if all the injectors are faulty.You can also remove the fuel rail and zip tie the injectors to the rail.Now turn on the fuel pump and look for leaks at the injector tips.If there's more than a couple of drops per minute the injector is faulty and needs to be replaced.
Keep us posted.

1fast97gsx

Would an injector resistance test help decide if there is one that's not opening / closing properly? Looks like the upper intake has to come off to even get to most of them so I'd rather not pull that unless I really need to. I'm assuming there is an injector harness somewhere on the backside of the manifold. Anyone have the wiring diagram so I know what pins / colors are for what?