i have a problem.(please help)

[ctwatson86]

i have a 93 mustang its an lx, it is a 4 banger and its a making a noise, a pinging noise in the combustion chamber and when it does this ping it smokes heavy sometimes white smoke and sometimes black.but it only pings when i lay ing to the gas real good when i take off. it has 124 thousand miles on it i have done a tune up to it.please if anybody knows what i can do to fix this or what is causing it please let me know. Thanks

[99DenaliMan]

This could be a numerous amount of things. Anything from to much timing advance, to bad gas, to a sticky valve or pistons. I haven't yet figured out how to upload pictures onto here from my computer, so I can't show you what the readings should look like. But the simpliest way to diagnose this----That I can think of off the top of my head anyways-----and without spending lots of money is to first do a "paper test" for this test you cant have any holes in your exhaust system. Get your self a 3 x 5 card. Put it about an inch from the exhaust at idle. it should blow out evenly at all times. if it sucks inward as one of your cylinders are firing this will tell you if you have a burnt valve. Also could indicate a misfire because of a lean air/fuel mixture. Remember a hole in the exhaust will also suck it in, so your exhaust must be in good condition..
If this test passes get a vacuum gauge, you don't need a fancy one---They are around $20 or less I think. Find where the vacuum hose is plugged on your intake manifold. Pull the hose off. Make sure you feel a suction (to make sure this is the right place to put the tester) watch the gauge. Vacuum should be somewhere between 17-21 hg of pressure. Then use the throttle body and rev the engine to 2500 rpm. The rpm should first drop a little then go higher than the idle vacuum. Also at idle watch the needle closely and record the results. It should have a steady vacuum pressure at idle (NOT bouncing from 17 to 18) etc. This may help with your diagnosis. For example a reading that drops all the way to 0 when accelerated and stays low indicates a restriction in the exhaust, a needle bouncing 1-2 in. hg can indicate an incorrect air/fuel mixture. This test can also tell if your valve guides are loose etc. Try this and post the results and I'll explain what the outcome means. Also if this test works out as fine, try a compression test. About $10--This test only takes about 15 minutes and can be as usefull as the vacuum test. Remove all spark plugs, remove air filter box from throttle body, block throttle body (so air doesnt get in and mess up compression test results, disable the ignition coil.ALWAYS GROUND THE IGNITION COIL WIRE TO THE FRAME. SIMPLY REMOVING IT WILL CREATE AN ARCH ACROSS THE COIL AND IT WILL BURN OUT WITHIN 6 MONTHS. Screw the compression tester into the first cylinder and crank the engine 4 revolutions. (listen to the engine) record your result. Try this again on the next cylinder, also post the results and I'll try to explain what they mean. (this test will tell you the condition of 3 things--intake-exhaust valves-piston rings--head gasket). Not sure what your vehicle specs are but they more than likely will be somewhere between 100 and 200 psi. If one cylinder is more than 15-20% lower than the other 3, do the same thing on this cylinder, but as a "wet compression test" put 1 tsp of oil in the cylinder spark plug hole. Crank it a few times then test again. If the reading goes up you have bad rings. if it stays the same it's probably valves-- if two cylinders next to each other are low it's probably a head gasket.


o yea check your timing first,, lol
Then again,,maybe it's just bad gas or timing someone else has an easier and better idea???????????????????