'99 Grand Am Problem

I have a '99 GA SE w/ 2.4L 4 cylinder and 81K miles. I got a tuneup and oil change about a month ago. Two weeks later heard a knocking sound from right side of the engine while driving on highway. Car ran fine, just a disconcerting knocking sound. Got home, did a quick check of fluids, were fine, nothing seemed out of ordinary. The noise would come and go and a few days later, Service Engine Light came on, took the car to the dealer who diag'd the code as P0301, Misfire, cylinder 1. They cleared the code, and said the knocking could not be diag'd unless they tore the engine down. That didn't make sense to me, so I took it back to where I got the tuneup and had them redo their work. They put the car on the computer and it didn't come up with any codes. The knocking still persists intermittently. The biggest difference when the knocking happens is gas mileage. One thing my son has noticed while we were trying to investigate the noise is that if you turned the steering wheel, it wouldn't completely go away, but it did get quieter. It seems to be coming from the right side (as you look at the engine from the front of the car) by the black cover plate that is above the alternator, air conditioning units. I have read a few of the posts and have checked the boots, added fuel injector cleaner, I took the air intake module cover off and checked it. I don't know if this is normal but there is a thick yellowish brown substance in the hose leading to the cover. The air filter looked clean. One thing I haven't tried is switching the injectors as some have suggested. I don't know how to do that. Any suggestions or ideas as to what this might be would be greatly appreciated.

Welcome to AF!!

There are three possibilities. One is cheap, one semi expensive the other very expensive. First, check the belt tensioner. It could have gone bad and is causing a knock. Second is the timing chain adjuster. Requires removal of the front cover. Might as well change the timing chain while you are there. Finally, a rod may be knocking. Will require an engine rebuild. Hope this helps!

Good Luck!