What causes an engine surge when the ECU is off?

If closed TPS voltage changes, the ECU may assume that your foot is on the throttle, causing a richer fuel mixture to be delivered. This can also be caused by a faulty TPS, or even a poor ground. With the engine off, check TPS voltage with the accelerator pedal relaxed. Then work the pedal a few times and see if the voltage changes.

What causes an engine surge during fuel injection?

In combination with the camshaft position sensor (CMP), the CKP signals are used by the ECU to manage fuel injection and spark delivery. A faulty CKP (or CKP circuit) can easily cause an intermittent misfire, which naturally results in what the driver may perceive as a surging effect.

When to set DTC for engine surge maintenance?

• After driving at 6.25 mph or more, the actual engine idling speed varies from the target idling speed by between 100 and 200 rpm, five times or more during a drive cycle. • If the actual idling speed varies from the target idling speed by more than 200 rpm five times or more during a drive cycle, the ECM illuminates the MIL and sets the DTC.

Why do the RPMs go up and down at constant speed?

It’s like the rpms are surging up and down but only between 30mph and 50mph. Then it levels off as I gain speed The RPMs surging under a constant speed in that 30-50mph band certainly sound like a torque converter lockup problem. It sounds like the torque converter is locking and unlocking again and again.

Can a cracked IAC valve cause an engine surge?

If the hose is cracked or damaged, the engine will react as though the IAC valve is faulty. Also note that Toyota and Lexus vehicles may feature a non-motorized, magnetic IAC valve, requiring periodic cleaning of the IAC air inlet. In order to isolate the issue, clear any codes, then disconnect the IAC and start the engine.

What causes an engine to idle up and down?

A malfunctioning MAF sensor can cause a wild up/down engine idle speed (say, 0-2,000 rpm). This might be caused by a loose harness connection or by a damaged or contaminated sensing wire. The MAF sensor measures the amount of air flowing through the throttle valve.

Why does my ECU think my foot is on the throttle?

Any deviation in throttle shaft position (due to shaft wear) will create uneven signals to be generated by the TPS reacting to this deviation. If closed TPS voltage changes, the ECU may assume that your foot is on the throttle, causing a richer fuel mixture to be delivered. This can also be caused by a faulty TPS, or even a poor ground.

How to fix a surging engine in a car?

Easy step by step guide on how to repair an automotive engine that is surging, this information pertains to most vehicles and is listed in the order of popularity. Start with the vehcile on level ground, engine “OFF” in park with the emergency brake set, wear protective gloves and eye wear for safety.

Can a faulty fuel pressure regulator cause a car to not start?

In the event your Ford cranks easily, but doesn’t start within the first five or six revolutions of the starter motor, you may have a faulty fuel pressure regulator. If the regulator has failed completely, the vehicle will crank, but not start at all.

What causes idle surges on a car ECM?

Idle surging can be caused due to other issues in the car, but if it happens in conjunction with other throttle position sensor symptoms, the culprit is often the TPS. At idle, the ECM will not get the correct information and the throttle will variate randomly causing idle surges.

Can a vacuum line cause an engine to surge?

Learn more Step 5 – If a vacuum line has caused a leak the engine will surge, as vacuum lines age they can become brittle and fall off the engine or accessory. Learn more Step 6 – If an air intake boot becomes torn and develops a leak it will cause the engine to surge.

What causes an engine surge when the ECU is off?