What happens: you start the Silverado and suddenly see that the RPM needle goes abnormally high on the gauge reaching almost 2000 RPM. After about 3-4 seconds, the needle goes down and the engine stops roaring that badly.
Hard engine starting highlights
- Level of urgency:Medium
- Can you drive?Yes, if it starts
- DIY inspection:Possible but complicated
- DIY repair:Mostly,impossible
- Price for repair:$200 - $750
- Common Reasons:Spark issues, carb problems, compression, engine problems
- Ways to fix:Inspect spark plugs, check compression, verify fuel supply is good
What are the possible reasons for this?
IAC (Idle Air Control). This is the valve that controls the amount of air supplied to the engine when idling. The valve is attached to the throttle body. This is the first thing you should check in this case.
Throttle body. It's very possible that the throttle body has an air leak and more air gets into the combustion chambers when you start the car.
Air supply adjustment problem. In older Silverado engines, you could adjust idle speed by screwing a certain bolt on the throttle body. If you did something wrong, the engine may freak out when you start it. Readjustment is needed.
Throttle position sensor. Another very possible culprit of high revving up when starting. This sensor tells the ECU about the position of the throttle body flap and it may lie to the ECU which will result in more fuel and air sent into the combustion chambers than needed.
ECU issues. It's not uncommon for older GM cars to develop problems with their ECUs. One burnt part of the unit may lead to changed mapping and issues with idling.
Of course, your idle air control valve or the throttle body may just be contaminated and require proper cleaning. This is one more very common problem that needs to be reckoned with.
DIY things to do when your Silverado goes crazy at engine startup
If you have some mechanical skills and know how cars work, you may avoid paying repair shops when this happens to your Silverado.
Here are some DIY methods to deal with the problem:
- locate the issue by using the scanner and also by checking the most common culprits one by one;
- clean the throttle body and also clean the idle air control valve - this will anyway be pretty helpful;
- if you see the check engine light, get the code from the ECU and see what happens with the engine sensors;
- check if the MAF sensor is OK, it may also cause problems with idling;
- when you locate the problem, just buy the needed part (better choose OEM) and install it.
Fortunately, replacing the idle control valve or the throttle position sensor is an easy job you can do. Don't forget to relearn the idle control valve if you clean or replace it. Please check with your driver's manual how you can reset the IAC or the entire throttle body because the process will differ from one engine to another.
Can you drive like this? Is it dangerous?
In most cases, you can drive your Silverado if it just freaks out when you start the engine. If one of the sensors or throttle body parts is malfunctioning, it shouldn't have a dreadful effect on other important functions of the vehicle.
Also, the problem is most likely to appear when the car is idling and it shouldn't be the issue when you drive the truck.
But if you experience problems like serious RPM fluctuations when idle or issues with the work of the engine when you drive, then you should drive directly to the good shop and have the car inspected. The tow truck will only be needed if driving seems to be impossible due to the engine going crazy in whatever mode you try.
How much is it to fix this?
Well, the best thing you can do is to try and inspect the car on your own and then find the problem. Sometimes, the fix is just a couple of dollars that you will spend on the solution for cleaning the throttle body.
But in most cases, you will need a new sensor or a new idle air control valve. In this case, the OEM valve or sensor may cost you quite a lot - $50 - $100 depending on the part you need. Anyway, you may install it on your own and will not need to pay for labor.
If you can't locate the issue and need to go to the dealer or shop, your expenses will start with $100 - $200 for inspection, up to $100 for parts, and then another $100 or so for labor. Doesn't seem to be a cheap problem to solve!
About the authors
The CarAraC research team is composed of seasoned auto mechanics and automotive industry professionals, including individuals with advanced degrees and certifications in their field. Our team members boast prestigious credentials, reflecting their extensive knowledge and skills. These qualifications include: IMI: Institute of the Motor Industry, ASE-Certified Master Automobile Technicians; Coventry University, Graduate of MA in Automotive Journalism; Politecnico di Torino, Italy, MS Automotive Engineering; Ss. Cyril and Methodius University in Skopje, Mechanical University in Skopje; TOC Automotive College; DHA Suffa University, Department of Mechanical Engineering
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