What causes engine revs to drop when idle?

What causes engine revs to drop when idle?

3) Once at normal operating temperature, the engine misses badly while idling. It idles smoothly for a second or two, then misses, which causes the revs to drop suddenly, and then the control system seems to increase the idle speed to counteract the drop in revs for a second, and then the cyle repeats.

Is the drivig engine smooth at low idle?

So smooth you could balance a coin on the engine even at low idle revs of around 650 rpm. In fact drivig with the TPS disconnected is quite acceptable, except that automatic gear change down does not happen (as expected). Have had the car for approx 13 years and has been a great, reliable family car.

Which is worse rough idle or perfect idle?

Very rough idle with a repetitive cycle that is smooth for a couple of seconds then misses badly, occasionally stalling. Worse problem is bad hesitation when accelerating after throttle at idle position, sometimes stalling. Worst after stationary idle, but also after moving at low to medium speed with closed throttle and then accelerating.

What’s the average idle speed of a car?

However, during normal driving over about 2000rpm and nomral traffic speeds is perfectly smooth – no missing, no roughness no lack of power, no excess fuel consumtption. Spent approx $2500.00 on two trips to mechanic, without improvement.

What causes rough engine idle or TDC code?

So, should the engine misfire, rough engine idle or (TDC) code; point to an air leak in the intake manifold gasket, following the below directions. A very common cause of a leaking intake manifold is the gaskets and bolts used from the factory.

Why does my car idle at 1500 revolutions per minute?

Older cars will try to compensate for worn spark plugs or a failing ignition coil by increasing the engine idle. An engine with a problem that is idling at 1500 revolutions per minute is far more likely to stay running than the same engine trying to idle at 800 RPM.

What’s the idle speed of a Nissan truck?

Most of them operate in a similar manner and regulate the engine’s idle speed using the same systems, so this information is useful for many car owners. I have a 1997 Nissan Hardbody with a 2.4-liter engine, manual transmission, A/C, and 89,000 miles. It idles at 1,500 rpm, which doesn’t go down after it’s warm.

What causes a truck to have a high idle?

Luckily, there aren’t too many things that can cause what’s commonly referred to as a fast idle problem. Some of the causes are super cheap to repair; others are serious bank breakers. You can usually figure out what’s causing a high idle problem and estimate the cost before you open your wallet.