weird knocking

[jon_570]

i have a 1997 toyota corolla CE with 137k miles on it...about a year ago it started knocking when under acceleration..i switched to 10w-30 instead of 5w-30 thinking the thicker weight would stop it..it kinda helped..i was running 87octane gas then..i thn switched to 89 ctance and it stopp almost completely..here my question..my car runs great..idels perfect goes through the gears with no trouble..but when i shut it off it makes this weird knocking sound..lets just say i pull into wal-mart and i open the door and i turn the key back..like half a second later theres a weird either knocking or vibrating kinda sound coming out from the engine..only when u shut it off though..starts up fine..what could this be..ive checked everything and everythings good and secure...what could it be..Thanks

Jon

[thespud]

It sounds like what you are describing is whats called 'Dieseling' Where the engine acts like a diesel and takes a bit to shut off. Have you checked the timing of the engine, plugs and wires?

[toyomoho]

Is the idle speed too high? In theory the engine cannot diesel without a fuel source. Are your injectors leaking when the ignition switch is off?

[jon_570]

idles at about 1000

[94_Rolla_Guy]

its definately idleing fast it can't really after run or diesel because the injectors shut down killing fuel....

try cleaning the throtle body do a good job take it off the car and disassemble it, clean the IAC valve on the bottom under whiteish box with electrical connection that will most likely fix the idle. also check the A/C idle up valve (two hoses and electrical mounted on firewall behind intake) as they tend to get stuck

Id check your timing it doesn't take much extra timing to make it knock. Also you may have carbon build up something like a seafoam treatment might help..

[jon_570]

whats the SEAFOAM treatment????