_GnarBro

My check engine light is on, and when im accelerating in any speed, I get this knocking sound, it's coming from my engine, but when I went to autozone and hooked the computer to it, it's saying my cats are going out. Would that be giving my engine the knocking noise since the catalytic converter is clogged and the engine is having to work too hard through it? I need help, I don't know much about cars and I don't want to get screwed over by a mechanic

robb15033

Well, I don't think the cats are the knocking issue. What I would do is get two cans of Seafoam. Put one full can in gas tank and use second one while car is running, put a straw in the Seafoam can and pull out the pcv valve and let the pcv valve suck out the Seafoam a little bit at a time till half of can is gone. Turn off car, let sit for 20-30 minutes and then suck in 2nd half of can. It will smoke a little bit. Also you just have to know if you have proper operating ignition parts. Brand new Autolite copper plugs, new plug wires (I use Granatelli MPG) of your choosin, and ignition coil (I installed a Screamin Demon when mine failed). Those two items (Seafoam & ignition parts) will help with any further diagnostics and help eliminate a bunch of second guessing. Lastly, make sure your oil is fresh and at proper level. Always listen for possible vacuum leaks around the EGR. Good luck, and please update soon.

03shadow

^lol you bath is seafoam dont you?

the cats may be throwing off readings of your O2 sensors and could be making the car run strange and make it knock. my experience with autozone/advance scanning for cats is that the code will tell you catalytic converters but in reality it may be the O2 sensor going out. only way to know is to replace, which sucks. or try robbs suggestion, i wouldnt do it though if your car has high miles and you have never done it before. other than that, do a tune up. good luck!

robb15033

Yep, love me some Seafoam. Almost 300K miles on the Mustang and my pet peeve is keeping up with the pcv system, Seafoam the intake at oil change intervals, and same with the fuel filter. All cheap items I like to pay attention to.

03shadow

yeah if you keep up with it like you do im sure there wouldnt be any problems. does yours even smoke anymore when you use it?

_GnarBro

I have new spark plugs and wires and ran seafoam in it 3 times about 2 months ago.

robb15033

[QUOTE=_GnarBro;7901660]I have new spark plugs and wires and ran seafoam in it 3 times about 2 months ago.[/QUOTE
Then I can not help.
Now, understanding that I can not speak with confidence at all, it sounds like a compression issue.
Can anyone chime in?? Please?

robb15033

I now have a catchcan in between the pcv and upper intake so no, not as much but it ALWAYS improves acceleration ect. when its in the car ever few months.