issue?
My Check Engine Light is on and my truck does not idle when cold. Do I need a new crankshaft position sensor or is this an ECM or timing chain issue?

Two years ago my truck backfired and would not run. I replaced the distributor, egr valve, mass airflow sensor, cleaned the intake and adjusted the throttle to idle slightly higher than normal.

Now my truck will not idle when cold, and sometimes will not idle when hot. Otherwise it runs great through acceleration. Check engine light says the crankshaft position sensor is bad but I replaced it as well and code remains after resetting.

So, how do I test all the electronics? Is it worth it or just get the timing chain replaced? I do not think it has been replaced at all.

Thanks!

My car h

Experienced mechanics share their insights in answering this question :
Hi there. Your vehicle has an idle air control valve that adjusts the idle via commands by the ECU. What it sounds like you adjusted was the throttle plate position when it was closed and had no adjustment on the actual idle. Adjusting the throttle plate rest position is similar to holding the gas pedal slightly to affect engine RPM. The idle air control valve (IAC) can stick over time and mileage, whether due to contamination buildup or simple wear and tear which will require replacement to correct.

Reset what you adjusted and replace the IAC for the idle concern. For the Check Engine Light, there could be an issue with the wire harness, ECU, or even the reluctor plate for the timing chain. This wheel has several notches, or teeth, with one gap, or wide tooth, that denotes cylinder 1 TDC, and provides the ECU with the position of the crankshaft. The ECU uses this information with a similar sensor for the camshaft, compares the two, and determines the relational position of the firing order, etc.

There should be a 5 volt reference available at the sensor; if not, there could be a break in the wire or the ECU is not sending the voltage. Check the wire harness for an opening or short and repair as necessary. If the harness is ok, I suspect either the reluctor plate has failed, the new sensor is defective, or the ECU has failed internally. I recommend having a certified mechanic, such as one from YourMechanic, assist you with a inspection of why car does not idle, a replacement of the idle air control valve, and a Check Engine Light inspection.

How to Identify and Fix Common car Problems ?

Our sources include academic articles, blog posts, and personal essays from experienced mechanics :

Toyota Tacoma Check Engine Light Flashing

Other common reasons for a Check Engine Light are faulty head gasket, faulty emissions control part, damaged oxygen sensor, a malfunction with the fuel injection system, dirty mass airflow sensor, or defective spark plugs to name a few.

Idling a car can cause carbon to build up on the spark plugs and inside the cylinder, which can in turn lead to a misfire or an underperforming spark situation. Either of these issues can lead to check engine lights.
Problem Description

The idle air control motors tend to become carboned up at around 100,000 miles and will cause a start and stall and/or stalling at stop sign problems. Many times these valves can be cleaned, however, the sure bet is to replace the idle air control motor and clean the throttle body.

The most common reasons a Toyota Tacoma has rough idle are a vacuum leak, an issue with the spark plugs, or a problem with the ignition coil.
Steps to Reset an Engine Light

It will have a black cap and a negative (–) symbol. Using a wrench, loosen the nut on the negative battery terminal and pull the negative connector from the battery. Keep it disconnected for 30 to 60 seconds. Reconnect the negative cable and re-tighten it using your wrench.

This is a sign you should stop driving and have your car looked at by a mechanic as soon as possible. Use your best judgment on whether to call a tow truck or drive yourself to a nearby repair shop. Is the light flashing? In many vehicles, there are two types of check engine lights—a solid light and a flashing light.
Will your check engine light turn off by itself? In most cases, successfully repairing the issue that caused your light to come on will cause the check engine light to turn off automatically—but only after 10 to 20 “cycles”.
A rough idling engine can be caused by spark plugs or spark plug wires. Spark plugs use the electrical current received from ignition coils to ignite the air/fuel mixture within the combustion chamber. A plug that is damaged or installed incorrectly can result in fuel being burned at an inconsistent rate.
Typically, the idle speed will be set at a value in the range of 600 to 800 RPM, but the exact value will depend on the number of engine cylinders and whether the vehicle is equipped with a manual or automatic transmission.
The system turns off the internal combustion engine when the vehicle stops at a stop light or during stop and go traffic where the vehicle would normally idle for a minimum of three to five seconds. The engine is then automatically restarted when the driver is ready to proceed.
Engine Misfires

Perhaps the single most common cause of rough idle comes in the form of a misfiring engine. As you may know, any automotive engine contains multiple cylinders. Each of these cylinders contributes to powering your car by combusting a mixture of gasoline and air.

Causes of a rough idle. Many different problems could result in a rough idle for your car or truck, including: dirty fuel injectors, clogged air filters, bad spark plugs, and a variety of exhaust system issues.
The check engine light is constantly on: Your vehicle`s onboard diagnostic system has determined something is wrong and needs to be fixed. Although your vehicle may seem to be operating fine, it`s best to bring it in for service as soon as possible to prevent additional issues.
These problems can range from faults within the electrical system, the engine, fluid levels or to problems within the car`s emissions system. The problem can even be as simple as forgetting to tighten your gas cap – in fact, this is the most common reason why check engine lights appear in the first place.

Relevant Questions and Answers :

the most relevant questions and answers related to your specific issue

My Check Engine Light is on and my truck does not idle when cold. Do I need a new crankshaft position sensor or is this an ECM or timing chain issue?
ANSWER : Hi there. Your vehicle has an idle air control valve that adjusts the idle via commands by the ECU. What it sounds like you adjusted was the throttle plate position when it was closed and had no adjustment on the actual idle. Adjusting the throttle plate rest position is similar to holding the gas pedal slightly to affect engine RPM. The idle air control valve (IAC) can stick over time and mileage, whether due to contamination buildup or simple wear and tear which will require replacement to correct.

Reset what you adjusted and replace the IAC for the idle concern. For the Check Engine Light, there could be an issue with the wire harness, ECU, or even the reluctor plate for the timing chain. This wheel has several notches, or teeth, with one gap, or wide tooth, that denotes cylinder 1 TDC, and provides the ECU with the position of the crankshaft. The ECU uses this information with a similar sensor for the camshaft, compares the two, and determines the relational position of the firing order, etc.

There should be a 5 volt reference available at the sensor; if not, there could be a break in the wire or the ECU is not sending the voltage. Check the wire harness for an opening or short and repair as necessary. If the harness is ok, I suspect either the reluctor plate has failed, the new sensor is defective, or the ECU has failed internally. I recommend having a certified mechanic, such as one from YourMechanic, assist you with a inspection of why car does not idle, a replacement of the idle air control valve, and a Check Engine Light inspection.

I have a 96 Ford ranger with cel p0340 I have recently done a timing belt, engine runs great replaced cmp sensor cel still on
ANSWER : Hi There,
This may happen for a couple of reasons. First, check to be sure that the connections to the sensor are clean and not faulty or broken. Secondly, check to be sure you replaced the correct sensor as there are two camshaft position sensors in some applications. If you need further help with this, please reach out to us here at YourMechanic as we are always here to help.

check engine light O2 sensor already replaced same codes still popping up after replacing old O2 sensor
ANSWER : Hi there. What you received from the parts store was a code retrieval, not a diagnostic. The codes are set when a fault is detected against normal operating parameter. The computer does not know what caused the fault, only that the fault meets the criteria for this code to set. There could be a problem in the wire harness, converter, or the ECM. The code and data are needed to properly assess the direction that a diagnosis needs. I strongly suggest having a qualified technician perform an inspection to avoid replacing unnecessary parts. Your Mechanic has several available technicians that can assist you with a check engine light inspection.

Venza 2010 L4-2.7L: My check engine light is permanently turned On. I have these codes P0012, P0016, P0017. What needs to be fixe
ANSWER : These are fault codes indicating problems related to the timing of your car’s engine. Normally the car will not run very well or sometimes not at all when these are on. I would suggest having an expert from YourMechanic come to your home to diagnose these trouble codes and potentially reset them to see if they register again. There are also sensors related to the exhaust as well. There is what is called an oxygen sensor which relays information to the car’s computer regarding the content of the exhaust gases which then tells the computer how to adjust the air/fuel mixture.

While driving on freeway truck goes into a limp mode, and the check engine light, abs light, parking break light, service brake
ANSWER : It is possible that you could be having an issue with your powertrain control module. This is somewhat of a common problem on many GM vehicles. I would recommend having your vehicle inspected by the dealership to determine if the powertrain control module is functioning properly. If not, a reflash of the powertrain control module may resolve the issue but often times it must be replaced.

Check engine light
ANSWER : Hello,
This kind of condition could be related to other things such as faulty fuel injectors, a faulty or dirty mass air flow sensor, or potentially a fuel pressure problem related to the fuel pump or fuel pressure regulator. The original diagnosis of the oxygen sensor being faulty would have been the initial correct approach, however the oxygen sensor may have been properly reading an abnormal fuel condition that is actually causing the rough idle. I would suggest having a professional from YourMechanic come to your location to diagnose and inspect your vehicle.

p0011 code,check engine light one, changed bank 1 vvt solenoid and check engine light still on?
ANSWER : The P0011 code is typically caused by oil issues with the car. I would particularly make sure the engine oil level is not low. The VVT solenoid relies on proper oil levels to do their job. If they don’t have enough oil, they won’t work. You can have a mobile technician from YourMechanic visit your home or office to inspect the Check Engine Light for you. If you follow through with a repair with us you will be reimbursed for the cost of inspection.

CHECK ENGINE LIGHT ON
ANSWER : The on board diagnostic (OBD) sets a pending code each time the ECU detects a problem. It confirms the code if it sees the same problem twice. So you’re really only dealing with the two codes : P0016 and 17.These codes are telling you that the timing between the crankshaft and the camshaft are off on Bank 1 (the driver’s side) cylinder bank. This could be a sensor error, a problem in the reluctor ring on the harmonic balancer, or a timing chain problem. Without doing a thorough diagnosis, it’s impossible to say what parts specifically need to be replaced. If you contact Your Mechanic, they can send a technician to your home or office to investigate the codes on you Mercedes and then let you know what it will take to fix it.