Skip the auto shop - Our mechanics make house calls

Q: Long crank time, low idle, and poor to no acceleration.

asked by on

Just replaced the engine due to being run low on oil. Although the previous engine was starting to knock, it accelerated and ran ok to the shop. After installing a used engine in the car, the car has a very long crank time before firing (but turns over well) and then has a very low idle (500-750 RPM) and throttle response is poor at best. Acceleration is so lacking that the vehicle can not be driven. In park I can get it to rev up (no odd noises). If I hold it at part throttle for about 2-3 seconds and then it will catch up but feels bogged down. I have changed out the electronic throttle body, spark plugs twice with two different gaps, fuel rail and all injectors, crank sensor, cam sensor, (all parts came on the used engine, and I have swapped them out for the ones original to the car with no change. Only part that is on it now that is not original to the car is the intake manifold itself) and checked all harness connections including MAF. There is no Service Engine Light on.

My car has 125000 miles.
My car has an automatic transmission.

A: Hi there, thanks for writing in. I'd be...

Hi there, thanks for writing in. I'd be happy to offer my insight. I would suggest checking the idle air control module. If the motor is starving for air (similar to an engine being choked at normal operating temp), this may cause it to bog down as you describe including the very low idle. As you may already know, if it were a leaner fuel condition such as a vacuum leak, the tendency is for the idle to naturally be higher.

If you would like help, consider having an expert automotive technician from YourMechanic come to your home or office to inspect and diagnose this issue for you, and make any repairs as needed.

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: Key locked in ignition.

Try a different key first. If the other key also does the same thing then try to move the steering wheel to the left and right to make sure it is not in a bind. If that does not work...

Q: Front end shaking.

The speed and conditions where the shaking occurs is the key to diagnosing this issue. For instance if the vibration starts occurring around 55 MPH and subsides after 65-70MPH this could be an indication of a tire/tires that are out...

Q: 1990 Toyota pick up 22re I just got it in time okay soon as you touch the gas feet it dies ever time so I gave up and its set for

This is typical of a bad idle air control valve. An idle air control valve allows the engine to idle properly by allowing the proper mixture of air and fuel at idle speed. This can also happen when there is...

Related articles

Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...
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.
P2103 OBD-II Trouble Code: Throttle Actuator Control Motor Circuit High
P2103 means there is a fault with the throttle actuator control motor circuit, likely due to a defective electrical component or part.