The problem I am having is in the daytime I am getting spark knock when I try to get on it, sounds like someone shaking a paint can in my engine. At night time when temps are cooler I can get on it with no problems. Did some research and tried changing my maf sensor, didn't fix it. Checked for vacuum leaks and saw 1 hose that goes from pcv to tb was ripped replaced it, still there. Tried changing the fuel filter, nothing. Ran seafoam through the gasoline, nothing. Tried the molar intake cleaner stuff, didn't work. Kind of at a loss for what it could be. The only thing I had added power wise would be a cat back exhaust. Tired of throwing money at this thing and coming up short. Been going around on here, using the search function and trying all the things people have suggested for other people, but I have not been able to find out the problem. Not throwing any codes or anything. Any help would be a appreciated.

 

You might get more accurate answers if you provide some details like what car it is? What the engine is? Mods done to the engine? Stock tune or modified?
Cold air intake or stock? Temperature difference between night time and day time?
My guess would be the tune (timing) is not setup for the higher temps but without details that's only speculation on my part.

 

Try running some good premium gas. Or some good octane booster. Or both. You might have some carbon build up inside the cylinders. You live in SoCal so it's definitely hot out right now. Your engine could be heatsoaking a little because of that too.

 

I always run 91 from shell, the highest we have here. Doesn't octane booster only raise it by like .2 or something? I thought I read that in here somewhere

 

Check if you're getting oil in the intake manifold (and check PCV plumbing for oil).

 

When I fixed the hose for the pcv, I did not see any traces of oil. Also tried to change to the other pcv people suggest to try. Does it have something to do with the tune then? Maybe for some odd reason it went out of whack? It used to run fine up until around this time last year. Some things I try and change and it seems it works for a little bit, but then it always starts to happen again.

 

Yes traditional octane boosters only raise like that, but a good race fuel concentrate like Torco Accelerator will take 91 to around 96 or so. Could also just mix in some unleaded race gas as an option as well

 

Did it just start? Have you gotten gas since? When I worked at a dealership, we saw a lot of problems with cars that ran shell and Arco gasoline. Try 76 or chevron. See if it changes.

 

Whats the wideband say?

please tell me you own a performance car it has a wideband, first and foremost.

 

Check inside the intake manifold for oil pooling on its floor.

 

If it just started happening, then something has changed, this has to be found.

 

I'd bet the intake and valves are caked with carbon. Get some Amsoil power foam and decarbon the intake. My wifes TA was doing the same thing and I pulled the intake manifold to change the gaskets, the intake was so full of carbon it was redicules. Car was pinging constantly while driving. Cleaned everything up and its quiet again.

 

Car is a 2001 Pontiac trans am Ws6. Mostly suspension mods, slp intake(new stock air filter) and a cat back exhaust. I had tried to chAnge to chevron, the problem still persists. Weather has been funky here, but about low 80s in the day, 60s at night. The amsoil stuff, isn't that the same as the mopar combustion chamber cleaner? Didn't have a chance to look in the intake itself this weekend had a wedding out of town 🤦🏻dum♂️. Don't have a wideband installed. Didn't know that it was a requirement.

 

No check engine light coming on? I had an old IROC camaro that acted real stupid when the MAF went out. The catalytic converters are ok? No vacuum leaks?

 

No check engine, cats are good. Changed maf recently, check for leaks visually, might have to see if my friend has the smoker to check it even better

 

When you replaced the cat earlier, did it come apart? I've seen the internals plug up a muffler. Try disconnecting the exhaust, before the cats if possible, and drive it. See if it changes.

Oops... Wrong thread