91 5.0 wont rev

[6801]

we rebuilt my buddies 302 the car ideles fine all day but when we rev it it stalls out. like it cuts out. we set the timming checked for vac leaks wnd fuel pressure any other ideas and played with the maf sensor with mo luck

[mooneye777]

What is the fuel pressure stats you got, and what source did you check it from.

[FFR428]

02 sensors hooked up and working correctly? Any engine codes pulled?

[ted dehaan]

better check codes first a good guess is the tps throttle position sensor that tells the ecm when you advance the throttle and richens the a/f mixture like a accelerator pump in a carb.....ted

[35chevy]

It sounds like a fuel delivery problem. 02's have no effect on the way it runs in open loop (cold). They are heated sensors and the computer doesn't really use the information from the 02's until closed loop(warm). S0, if it doesn't rev cold I'd rule those out. I would check the TPS, Fuel pressure, and the mass air. Any of those three will cause it to bog from lack of fuel. If it's a Mustang the 10 pin connector in the wiring harness behind the intake is known to cause all sorts of issues from poor connection. The coolant temp. sensor, intake air temp. sensor and the map sensor would all cause idle issues so I'd probably rule those out. There is a ground that bolts to one of the bolts on the rear of the intake you might want to check. I believe the wire is orange if I remember correctly. If you can't find the problem and you don't have access to a scan tool, You might want to let someone take a look inside the computer. Codes don't always tell you much especially on the EEC-IV system but a look in the datastream at the voltage on all the sensors usually does the trick, if you know what to look for. A lot of people with a scan tool are no better off than a guy without one.......AUTOZONE for instance........they are just trying to sell parts. They think if you have an 02 code you need a new a new sensor.......RETARDS.....the sensor has a job...the computer sets the code when the sensor is reading out of range.....doesn't mean it's a bad sensor. Nice way to sell parts though. Maybe if I owned a parts store I'd read codes for free too. Anyway, let someone check it that has a clue.