Changed plugs Cleaned throttle body of carbon buildup
I have a slight (my wife can not hear it) knocking sound from my engine when accelerating from a complete stop. This only happens with the a/c on AND when the truck has been drove 25 to 40 miles. It seems (I think) to only happen when the outside temp. is above 90 degrees because I don't notice it on my way to work in the morning. The Haynes repair manual says to replace plugs, which I did, and check the injectors. The injectors seem to be OK since they are making the tapping noise using a listening tube. The manual also says it could be ignition timing off a little, the book also says it can not be adjusted either. Other than starting from a complete stop it does not seem to make the noise accelerating when passing or going up hills. Any ideas?