Dave Wick

I have an '89 5.0 5-speed Mustang with 124K miles on it. Under full
throttle acceleration in first gear the engine dies out somewhere above
3,500 RPM. It almost feels like a rev limiter, valve float or fuel
starvation. However, if I cruise on up to 5,000 RPM at a bit more leisurely
pace, it runs fine. It's only under full throttle and only in first gear
that I've had the problem. What's up?

Some additional background; 3.73 gears, full aftermarket exhaust, K&N fender
mounted cold air kit, 1.7 rockers, underdrive pulleys. All air and fuel
metering components are stock and original except for an aftermarket fuel
pressure regulator. TPS setting was verified today at .997 volts. The long
block is stock and original except for the 1.7 rockers. I'm still running
the original fuel pump although the fuel filter has been replaced.

Thanks!
Dave

Michael Johnson, PE

Dave Wick wrote:
> I have an '89 5.0 5-speed Mustang with 124K miles on it. Under full
> throttle acceleration in first gear the engine dies out somewhere above
> 3,500 RPM. It almost feels like a rev limiter, valve float or fuel
> starvation. However, if I cruise on up to 5,000 RPM at a bit more leisurely
> pace, it runs fine. It's only under full throttle and only in first gear
> that I've had the problem. What's up?
>
> Some additional background; 3.73 gears, full aftermarket exhaust, K&N fender
> mounted cold air kit, 1.7 rockers, underdrive pulleys. All air and fuel
> metering components are stock and original except for an aftermarket fuel
> pressure regulator. TPS setting was verified today at .997 volts. The long
> block is stock and original except for the 1.7 rockers. I'm still running
> the original fuel pump although the fuel filter has been replaced.

First thing I would do is pull any trouble codes from the computer.
Looks like the problem is occurring while the engine is at a high demand
for fuel. It could be a bad fuel pump, clogged fuel filter, improperly
set fuel pressure regulator or even clogged injectors. Also, check the
fuel pressure to see if it is within spec at idle and when the problem
occurs.

It could also be something wrong in the electronics (MAF, TPS, IAB,
various sensors, distributor electronics, etc.) but for me those
problems are difficult to detect and that is where I take it to a good
mechanic.

.boB

Dave Wick wrote:

> I have an '89 5.0 5-speed Mustang with 124K miles on it. Under full
> throttle acceleration in first gear the engine dies out somewhere above
> 3,500 RPM. It almost feels like a rev limiter, valve float or fuel
> starvation. However, if I cruise on up to 5,000 RPM at a bit more leisurely
> pace, it runs fine. It's only under full throttle and only in first gear
> that I've had the problem. What's up?
>
> Some additional background; 3.73 gears, full aftermarket exhaust, K&N fender
> mounted cold air kit, 1.7 rockers, underdrive pulleys. All air and fuel
> metering components are stock and original except for an aftermarket fuel
> pressure regulator. TPS setting was verified today at .997 volts. The long
> block is stock and original except for the 1.7 rockers. I'm still running
> the original fuel pump although the fuel filter has been replaced.
>
> Thanks!
> Dave
>
>
My first guess would be a bad fuel pump. It's hard to test for that, because
you need to check the pressure while it's under a heavy load. After 16 years and
124K miles, I'd just replace it.

--
..boB
1997 HD FXDWG - Turbocharged!
2001 Dodge Dakota QC 5.9/4x4/3.92
1966 Mustang Coupe - Daily Driver
1966 FFR Cobra - Ongoing project