Skip the auto shop - Our mechanics make house calls

Q: 4.0 lt is very sluggish. no exhaust restriction, fp is ok 45psi, all new tune up.

asked by on

This is a 4.0 lt 94 ford ranger. The engine is very slow to come up to speed and doesn't have much pickup speed on the highway. The exhaust has been checked, has new plugs, wires, coil pack. air filter checked, maf sensor cleaned. I have a 3.0 v6 that will run circles around this 4.0. Probably something simple but what?

My car has 107000 miles.
My car has a manual transmission.

A: Hi there. What you're describing may be...

Hi there. What you're describing may be an underlying fuel pressure concern. Check for any stored codes in the engine computer before replacing any more components. If there are no stored codes, a diagnostic tool will be required to monitor the voltage fluctuations for the MAF sensor; sometimes cleaning the sensor does not correct improper readings and the concern will continue.

If the MAF is ok, I would definitely suspect a low fuel pressure concern. This could be caused by a restricted fuel filter, restricted fuel line, or a weak fuel pump. A fuel pressure gauge can be connected before the filter to check for a weak fuel pump and after the fuel filter to check for a restricted fuel filter.

A bad fuel pressure regulator could also be the cause if the fuel pump and filter check ok and would need to be inspected by a qualified technician. YourMechanic has several technicians available to provide a low engine power inspection for proper diagnosis.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Save up to 30%

Get a quote

What others are asking

Q: Steering shaft cover melting

Hello there. Thanks for writing in about your 1997 Chevy C2500. There are a few possible causes for the heat issues you have. Headers perform better at higher RPM's than many stock cast exhaust manifolds. They do this in part...

Q: Low mileage but lots of trouble starting

The fuel systems on most new vehicles have a high pressure fuel system, including your Nissan Versa. This fuel system needs to keep fuel pressure at the fuel injectors in order to keep your engine running. When you shut off...

Q: Losing power but it's not in the engine more like bad connection

This vehicle may be having issues with the wiring connections to one or more modules of the vehicle having fretting corrosion. I would recommend disconnecting the battery and going to the ECM, ICM, BCM and disconnecting the connectors. You should...

Related articles

How Do Power Car Windows Increase Passenger Safety?
Power windows are responsible for approximately 2,000 emergency room visits every year. When a power window closes, it exerts enough force to bruise or break bones, crush fingers, or restrict an airway. Though...
How to Renew Your Car Registration in Oklahoma(DELETED)
Having your car registered with the Oklahoma Tax Commission is an important part of driving legally in this state. You will need to do this within 30 days of moving to Oklahoma...
How Much Does a Mechanic Make in Vermont?
Automotive technician jobs in Vermont have an average mechanic salary of $37k, with some mechanics earning a salary of $53k.