Q: Car sputters and backfires under load

asked by on August 19, 2016

I have an 88 mustang with a new cam, springs, coil, distributer, fuel pump, spark plugs, wires, timing chain and I'm having a sputter problem if I go over 3500 rpm and if I keep pushing it it will backfire. Then when u let rpms come back down it continues to sputter till u turn car off and back on. Then it's good till u go over 3500 rpm again?

My car has 292000 miles.
My car has a manual transmission.

Engine is sputtering Inspection $94.99 - $114.99 Get a Quote

This sounds like one of the valves are sticking or a spring is weak or broken. You may also have a lifter that is holding the valve open after you go to 3500 rpm and will continue to hold open the valve until you shut off the engine and oil pressure gets off the lifter. You may have to check the push rods and lifters for clogged passages. If you would like to have this checked in person, an expert from YourMechanic can come to your car’s location to diagnose the sputtering issue and determine what repairs are needed.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $70/hr

What others are asking

How do you fold down the rear seats in a 2012 Honda Civic?
Your car’s rear seats are designed to fold down to provide you with more room for hauling gear or other items. Doing so is actually pretty simple, and here are the steps you need to follow: Take the center rear...
2006 Pontiac G6 smells like gas
Fuel leaks are never good. A leak in the right place has the potential to ignite quickly. Gasoline is especially dangerous in its vapor state because this is when it is most explosive. The fuel pump does have an o-ring...
All lights come on and the gages, radio, heater, window wipers don't work and car won't come out of park.
This is a known issue with the Chrysler Pacifica related to a shifter interlock mechanism that sits down in the shifter console. This is a small plastic piece with a hook on the end of it connected to a spring....
Was cranking car and it just stopped. There is new battery. Lights horn are functioning, I get zero respsponse when turning key
Hi, thanks for writing in. You need to see if the starter has main battery power to the large terminal of the starter and then ignition power when the key is turned, getting to starter solenoid small terminal. If there...
My truck cranks but does not start - 1997 Dodge Dakota
Hi there. Usually, a no start issue is caused by either fuel or spark - not both. When this occurs, it's typically an issue with the central ECU (https://www.yourmechanic.com/article/what-is-a-vehicle-s-electrical-control-unit) failing to send the right signal to fuel related components and...
My 2004 Ford Focus is having electrical system problems
Hi there: It's very difficult for us to diagnose an electrical problem remotely, however, in general, the situation you experienced was mechanical in nature. When the starter solenoid is damaged or malfunctions (https://www.yourmechanic.com/article/symptoms-of-a-bad-or-failing-starter), it continues to run (which is what...
Horn is extremely sensitive after putting it back in the steering wheel.
Hi there. See if the springs were installed properly to the horn. Also, check to see if the wiring to the horn was tight and not loose. A return spring on a horn button will sound the horn sooner with...
2006 Ford Escape oil pan is sweating, is it the gasket or is it the pan?
Well I'm not sure about the mechanic's use of terms. If the oil pan is "sweating" oil, then that would dictate that the oil pan is already porous. It's not an everyday thing to happen but I have seen it...
Blinkers and brake lights
The problems you described may have different causes that will need to be checked separately. The headlights may be switch or wiring to lights or even the bulbs. The right front turn signal may be just a bulb needs replaced...

Related articles

The Best Used Cars to Buy If You’re a Caterer
If If you are in the catering business, you need a reliable vehicle that will provide you with what you need to transport your food, linens, and other supplies. Generally speaking, you're better off buying gently used, because you will...
The Best Used Cars to Buy If You're Towing a Boat
If If you’re towing a boat, the vehicle that you buy is largely going to depend on the size and weight of your boat plus trailer. Most cars, realistically, aren’t cut out for the job. We recommend a pickup truck...
Understanding Ford Intelligent Oil-Life Monitor (IOLM) System and Lights
Car symbols, or dashboard lights, are a car service reminder. The Ford Intelligent Oil-Life Monitor indicates when and what service your car needs.