I have a 300 six 4x4 Aod FI and it has developed a miss when there is no load on the engine. If I hit the slightest uphill it will pull flawlessly. I can pull a grade in OD at 40mph with absolutely no miss but at the slightest down grade with the engine under no load it misses. It almost feels like its surging or cutting out completely. I've changed plugs, wires, cap, rotor, Map sensor and throttle possition sensor to no avail.

 

I had that probablem but it was the map censer, another thing I was told at the time was to change that modual at the bottom of the distribitor. may work...

 

I am having the same problem with my 90. I have a new motor in it and had to disconnect the MSD because it only made the miss more noticible. Specifically, mine misses between 1600-1900 rpm and 15-19" of vacuum. If I put the motor under any load at all it runs like a champ. I have changed the vacuum lines, plugs, wires, coil, cap and rotor and found no success. I am curious, are you getting any codes on the computer? You changed the MAP sensor, how did you decide to change it?
Has your gas mileage suffered?

 

>I am having the same problem with my 90. I have a new motor
>in it and had to disconnect the MSD because it only made the
>miss more noticible. Specifically, mine misses between
>1600-1900 rpm and 15-19" of vacuum. If I put the motor
>under any load at all it runs like a champ. I have changed
>the vacuum lines, plugs, wires, coil, cap and rotor and
>found no success. I am curious, are you getting any codes
>on the computer? You changed the MAP sensor, how did you
>decide to change it?
>Has your gas mileage suffered?

I am getting codes from my computer. I get a 44 (Problems in Thermactor Air Control System) and a 29 (Vehical Speed Sensor signal voltage is too low). I don't trust the vehical computer because I bought this truck with a new engine (remanufactured) two years ago and when I bought it it was getting 8 mpg. and after many mods I got it up to 13.5mpg and that was with the c6 tranny. I put in an aod and its (miliage) has been very erratic. It was up and down with the c6 which told me something else was going on causing my miliage to fluctuate so much. I found that both the front and rear catalyst was clogged. Gutting the front and putting one of those low restriction catalyst made the truck a rocket, it now realy pulls strong but the miliege didn't go up and the computer never saw the exhaust restrictions.
I found that my truck misses at any small throttle opening situation and increasing the load makes it run smooth.?? I changed the map sensor because I thought the problem was connected to vacuum changes which the MAP senses from the intake manifold. I put in one of those high output coils which also made the miss more pronounced. My tank miliage went from 180 to 200 miles about 1mpg increase.

 

on your code 44, i would assume you have checked the vacuum hoses. I had to replace the TAD and TAB solenoids (sometimes referred to as air management solenoid(s) 1 & 2). I would check these solenoids electrically and make sure they are working correctly. They are towards the back of the valve cover on the drivers side of the engine under the EGR valve. The other thing to check would be the EGR vacuum solenoid whick should be just under or next to the TAB/TAD solenoids. It is black and has a round top. This top can be unsnapped and you'll find a filter inside that sometimes needs to be cleaned out in the kitchen sink. It regulates the vacuum going to the EGR valve and if it is clogged can cause some odd problems. I have a neighbor who had your VSS code come up on his 95 (with the mazda tranny) and we pulled the connector from the sensor, cleaned the oil off it, put it back together and the code disappeared.