What Causes Detonation - Advanced Or Retarded Timing?

[hoorders]

Hey guys,

 

My new to me 93 yukon with the 5.7 seems to have a little 'ping' under acceleration. I just gave it a complete tune up and its running great.

 

I haven't checked the timing(never done this before) but I was wondering if 'ping' or 'detonation' is caused by advanced or retarded timing?

If I check it(need to learn how) or get it checked, what should the timing be set to so it runs at its best. Its completely stock.

 

Thanks.......

[Gregorio]

Generally, advancing the timing will cause more detonation but there are a slew of other problems that can cause it too.

[kawtoy_77]

advanced timing, crappy gas will cause it too.... I don't know the timing off the top of my head, but most generally I refer to a CHILTON's manual for info like that. To set it by the book you will need a timing light. You may even be able to call your local dealership and have them tell you. I usually set it by ear... leaving the hold down bolt on the distributor loose enough I can turn the whole thing by hand and adjust it a little bit... then drive and see how it reacts. The pinging should get worse one direction, and better the other.

[gmtech4]

unplug the brn wire under pass dash,set timing to zero (deep vee shape in timing plate over balancer ),plug connector back in,clear any code if nessesary.

 

get better fuel,

 

check sticker under hood ,says the same

[Westlotorn]

The 93 350 used Throttle body Fuel Injection, good for torque and gas mileage but really just a fancy carburator.

 

Detonation is common with advanced timing, never with retarded timing. The 350 engine used a distributor and plug wires, unlike the newer 4.8, 5.3 and 6.0. Coil on plug design.

 

You may have a plug wire misfire, this is common if they are old, wires can fire the wrong plug if they are old or have worn spots. Open the hood in the total dark and take a look, you should not have a light show from your wires.

 

Too hot of a spark plug will cause detonation, stay with the factory heat range on these fuel injected engines. The FI engines always run on the lean side leaving them prone to detonation. Knock sensors will detune the engine for you when they sense detonation going on this costs you power and gas mileage but may save the engine from damage. Is the Knock sensor working?

Is this engine stock? The computer is looking for stock compression in its programing, if somebody slipped flat top pistons in the game has changed.

 

Might be time for a normal tune up set the timing as instructed and check your O2 sensor to make sure it is giving your computer the right information.

As said earlier in this forum, many things can cause detonation

 

Another potential cause of detonation, if a Catalytic converter gets plugged up the backpressure builds heat in the engine, increased heat can cause detonation. The test for the cat is simple, they plug a pressure tester in the O2 sensor hole and drive your vehicle, if the pressure is high the problem is solved with a new cat. This usually shows up by power loss while working the engine hard.

[VRSCA1]

Hey guys,

 

My new to me 93 yukon with the 5.7 seems to have a little 'ping' under acceleration. I just gave it a complete tune up and its running great.

 

I haven't checked the timing(never done this before) but I was wondering if 'ping' or 'detonation' is caused by advanced or retarded timing?

If I check it(need to learn how) or get it checked, what should the timing be set to so it runs at its best. Its completely stock.

 

Thanks.......

 

Don't forget to check the EGR valve operation,vacuum supply and the egr solenoid operation,The egr passage way inside of the intake was prone to plugging up with carbon on high mileage 5.7L engines.Quick check of the passage would be to lift up on the egr valve at idle,should idle rough and want to stall.Be careful its HOT! Use gloves.Also check the knock sensor operation,easy way to do this if no scan tool is handy,use a timing light with the est bypass plugged in tap in the area of the knock sensor(located rt side of engine block) using a mettalic object and watch for the timing mark retard move back towards the 0 mark it should move when the tapping is picked up by the sensor.

Another issue could be carbon deposits on the pistons and valves,decarbonize the engine.Also try going from 87 to 89 octane see if it helps.In addition to the other suggestions posted here.

[Westlotorn]

Great points, Thanks for cleaning up my offering. GM Sells a carbon remover that does a pretty good job of taking the carbon build up off the pistons and valve chamber. Follow directions if you choose this it puts out a ton a stinky smoke out the tail pipe. I had to use it on my 95 Suburban to bring down the knox so I could pass smog.

[dwilsonjr74]

Thanks for the information. Learned a lot though.