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Matt
Matt, Engineer
Category: Chevy
Satisfied Customers: 20608
Experience:  Honors degree in Mechanical Engineering, worked 8 years as a Formula 1 engine engineer.
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Want throttle past ldle knocks, 2004 Silverado want throttle

Customer Question

Want throttle past ldle knocks
JA: What is the model/year of your Chevy?
Customer: 2004 Silverado want throttle past idle knocks duramax diesel
JA: How old is the engine? And when was it last serviced?
Customer: 2004 @1month ago except fuel and trans filter
JA: Are you fixing your Silverado yourself? What have you tried so far?
Customer: Basic check and used code reader but no code
JA: Anything else you want the mechanic to know before I connect you?
Customer: It did this Saturday I cut it off pulled keys out restarted it worked all day Sunday it did it again cut of restarted worked till Tuesday has not powered up since
Submitted: 3 months ago.
Category: Chevy
Expert:  Matt replied 3 months ago.

Hello

if you have a lot of combustion rattle / noise then the 1st thing to try is some injector cleaner as a clogged or dribbling unit can give poor combustion

if this is OK then check the connections to the EGR valve, if either the vacuum pipe of electrical connection are damaged / corroded then the EGR can be on all time which certainly will hurt performance. Its also possible that its a fault with the EGR valve so its worth removing the valve and cleaning it out with brake cleaner, if it looks particularly clogged then replace it.

If the above are all OK then try checking for airleaks after the airflow meter, any air dragged in here isn't 'seen' by the ECU and so not compensated for and leans the engine out causing rough running. As its a mechanical fault it tends not to turn on the fault light and you can sometime hear a 'hissing' noise with the engine running.

Check the hose clips for tightness and inspect the trunking for any cracks or splits and also all the vacuum system, the small bore pipes and fittings for cracks and missing parts.

The best way to locate a leak is to have the engine running and warm and then spray lighter gas around each joint in turn. If the engine rev's up you've found your leak.

Work your way through each possible joint one at a time and you should find it. I use a slightly flattened piece of brake pipe and some rubber hose from the can of lighter gas to provide a spraying 'wand' and allow a direct blast of gas into each area, especially those difficult to reach with large implements.

Might also be worth checking the wiring and connector to the airflow meter for any signs of corrosion or damage. you can do a quick fault find if you unplug the meter and run the engine without it.

if the engine condition is the same then chances are the meter or the connection to it is faulty

its also worth cleaning the airflow meter by removing it from the car and spraying the exposed sensor wires inside the tube with a brake or switch cleaner - ensure that the cleaner is one of the old fashioned, non Eco type that does not leave a residue

On no account touch the sensor wires with anything physical as they are extremely fragile

Expert:  Matt replied 3 months ago.

Hi

do you still need help?

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