WesDe

My 94 5.O makes a strong rattling noise when warmed up and hard accelaration. It sounds like detonation, and I don't know what gives. I have changed coolant, termostat, wires, plugs. Reset timing back to stock and only use 93 Shell octane gas. Engine has about 110k on it. When car is not warmed up it runs perfect. Could it be fuel pump? mine is stock and noise. Please, please help me.

Thanks
Wes

acidman2

what does the oil pressure gauge show?? is it lower when hot or what?? is the whole car stock or were you just talking about the fuel pump??

WesDe

The car mostly stock with bolt ons. Nothing major. the oil presure is stedy in normal. The fuel pump is stock. Temp never goes pass middle, but it rattles after it warms up. Many people tell me that it is not fuel pump because it either works or it doesn't. I don't know maybe it is not supplying enough gas when hard acceleration.

roundman

try another brand of 93 octane gas from someplace besides Shell and see what this does.
if it stops, then it was the gas. if it don't, then you may need to drop the timing back 1 degree or so and see if this stops it. it could also be a build up of carbon on the valves and tops of the pistons. sometimes you can remove some of this by carefully spraying some water into the throttle body while reving the motor up to keep it from stalling. the water turns to steam and this helps knock some of the carbon deposits off the inside of the combustion chamber. a bad build-up will actually increase the compression ratio which can lead to pre-ignition or detonation. you will be surprised to see how much junk will blow out the tailpipes when you do the water thing.

WesDe

I think that this sounds more like it. I have also noticed that even at idle I can hear a very light tapping noise which sounds like a valve ping. i will try the water. Do you think carb cleaner or other chemical would be better or water? Thanks for the tip, I will try the water and see what happens.

Thanks again

Moosetang

Some of that Foam stuff might work

WesDe

Roundman, I bought a can of special de-carbon cleaner from Ford. I did the procedure and the engine sounds a lot better now. I'm still hearing pinging but it it a lot less than before. I also retarted the timing by 1 degree and put diferent 93 gas. It did not make a difference so I put the timing back to stock. Im wondering if I should repeat the procedure again and use another can of cleaner. I don't know if that would be too much for the valves and seals. I will also change the plugs to platinum. i might even do the fuel pump just in case. if you guys think of anything else please let me know.

thanks for all your help. I want to get this pinging out so I can use the spray again. I'm affraid I might blow something the way its running now.

THANKS AGAIN.

roundman

I would really try it with just plain water and repeat it several times. The water won't burn like carb cleaner and it's the steam that knocks loose carbon deposits. If it's still pinging you need to retard the timing until it stops or you could really do some damage, especially if you spray it! lack of fuel is not what is making it ping, it's high cylinder pressures that cause most detonation and that's why you need the high octane gas to prevent it, the octane don't add power, it just lets you run at the verge of detonation without actually detonating. set the timing back down to where it ain't pinging and then take the car out and really blow it out a few times as this will also help knock off some of the deposits too. it would really help if you could rig up a way to inject some water while you're under a load at WOT. maybe you could rig up the windshield washer pump to add some water into the intake after the air cleaner somehow.

WesDe

Thanks roundman, I will try the water and I found a way to hook up that windshield pump to the intake. I will try that and see what happens. I dont know about the timing. The car runs really slow when I retard it. I guess I will just put it back when Im trying the water so i can really run it hard. If it stops pinging then i will bring it back to stock. I have been runing the car at stock 10 degrees because of 100 shot nitrous. Do you think that I should retard it from now on even if the pinging stops. I just dont want to take a chance and blow the motor.

thanks for your help

vfast

well first 10 degree with a 100 is too much..2 nd I'd say a timing chain replacement is in your future