Q: Runs rough below 3000 rpms

asked by on

Replaced valve seals timing chain and intake manifold gasket....head gaskets as well start up the vehicle has shaking rough idle but clears up after 2500 rpm.. 3000 rpm is perfect. The test drive feels like decent low rpm is crap... also would like to know if I have a wire in the wrong spot do not have a diagram for coil to plug..No smoke I'm about to set it on fire and push it over a cliff no intake vacuum leaks.....idk what to do (will a off timing chain allow it to idle rough and be perfect at 3000 rpm????)runs sooo smooth at exactly 3000 rpm, also will this idle clear up after being driven?? It seems to (almost) disappear after warm thanks Matt 9807299880 My car has 187000 miles. My car has an automatic transmission.

My car has 187000 miles.
My car has an automatic transmission.

This may be a sign of a faulty MAP sensor as the vehicle responds adversely to a load put on the motor (i.e. putting it in gear, making turns (which makes use of the power steering pressure switch) turning on AC or engaging the brakes). 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 engine is working hard, intake vacuum drops as the throttle opens wide. The engine takes in more air, which requires more fuel to keep the air/fuel ratio in balance. When the computer reads a heavy load signal from the MAP sensor, 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 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. I would recommend having an expert from YourMechanic come to your location to diagnose and inspect your vehicle.

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. Runs rough below 3000 rpms

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: abs light stays on and transmission shifts hard and idles eratically

Hey there. The ABS light and transmission shift problems may be from the speed sensor in the rear end is not reading correctly or the rear end has worn carrier bearings. You should have the ABS tested and codes diagnosed....

Q: Car runs rough in rain or humidity

If your car is running rough under wet or humid conditions, this may be indicative of a problem with the vehicle's mass airflow sensor, or perhaps one or more of the ignition coils. As these problems are electrical in nature,...

Q: Air conditioner won't get cool

Hello. The most common cause of the air conditioning coming out hot is the blend door inside the dash, or low refrigerant levels from a leak in the air conditioning system. A qualified mechanic,like one from YourMechanic will be able...

Related articles

How Long Does a Distributor O Ring Last?
The distributor is part of the ignition system in your vehicle and its purpose is to route high voltage from the ignition coil to the spark plug. The spark plug then...
P0240 OBD-II Trouble Code: Turbocharger Boost Sensor B Circuit Range/Performance
P0240 code definition Turbocharger Boost Sensor B Circuit Range/Performance What the P0240 code means P0240 is an OBD-II generic code triggered when the Engine Control Module (ECM) detects the intake boost...
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...