Q: Q: Rough idle and RPM fluctuation

asked by on

So here is my issue I was on my way home last night and the roads were slick and I was sliding quite a bit and all of assuden my truck started to want to die and at every stop sign I would have to restart my truck when it does idle it idled at like 500rpms sometimes lower and when you let off the gas while driving or just in park it will dies most of the time I hooked it up to a code reader and the only code I found was an issue with the map sensor so I replaced the map sensor but I'm still having the issue

My car has 185000 miles.
My car has an automatic transmission.

Hi There, As you may know, the Manifold Absolute Pressure (MAP) sensor senses engine load and generates a signal that is proportional to the amount of vacuum in the intake manifold. The engine computer then uses this information to adjust ignition timing and fuel enrichment. When the computer reads a heavy load signal from the [MAP sensor]((https://www.yourmechanic.com/services/manifold-absolute-pressure-sensor-map-sensor-replacement), it adjusts the fuel mixture to slightly more rich than normal so the engine can produce more power. The computer will then retard (back off) ignition timing slightly to prevent detonation (spark knock) that can damage the engine and decrease performance. This may also be caused by other closely related components such as a dirty or failing mass air-flow sensor, a faulty throttle position sensor or potentially a vacuum leak.

Was this answer helpful?
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
  1. Home
  2. Questions
  3. Q: Rough idle and RPM fluctuation

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

Get a quote

What others are asking

Q: IDL - RPM is higher then normal

You should first check to make sure you do not have any vacuum leaks. Scan the computer and diagnose any service codes. If you do not have any codes, then you may just have to relearn the idle of the...

Q: Bad gas in tank of 2008 Toyota 4Runner

The first step in dealing with bad gas is removing it from the fuel system as quickly as possible. This will help prevent further damage to any of the fuel system components. To do this, it will require that the...

Q: Q: Rattle noise

Hi there. Either the engine's timing tensioner is loose and not pressurizing up when the engine is started up or the camshaft variable timing solenoid is sticking when the engine oil is thick - cold. I recommend putting in an...

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...
What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...