1999 ranger spark advance

[Tell1999]

Hi I have a 1999 ranger xlt,AT, 4.0 engine.
The engine starts and runs nice, but after it warms up it starts pinging. I put a scanner on it and watched the advance when started I'd is around 14 deh after running a while it goes to higher while still idling. Driving around at slow speed it advances up to 34 deg. And the engine starts pinging quite loud. It I then stop and restart the engine it runs nice with around deg spark advance. After a few minutes the timing advances again and the engine starts pinging again. No engine codes. So far I have cleaned the maf sencer, replaced the crank sensor,replaced plugs.nothing seems to help. Any ideas?

 

[imp]

Hi I have a 1999 ranger xlt,AT, 4.0 engine.
The engine starts and runs nice, but after it warms up it starts pinging. I put a scanner on it and watched the advance when started I'd is around 14 deh after running a while it goes to higher while still idling. Driving around at slow speed it advances up to 34 deg. And the engine starts pinging quite loud. It I then stop and restart the engine it runs nice with around deg spark advance. After a few minutes the timing advances again and the engine starts pinging again. No engine codes. So far I have cleaned the maf sencer, replaced the crank sensor,replaced plugs.nothing seems to help. Any ideas?

Quick fix: fill tank with higher octane gas, or dump a gallon of 95% alcohol (Ethanol) into the tank when it's at 1/4 full, see if the ping goes away. That would be like E25 or so, which might coincide with maybe 89 Octane instead of the usual lowest 87. 2 Octane points might just do the trick.

 

[Tell1999]

Thanks that would probably work until someone can help me figure out what's causing the spark to advance that much 27 to 34 deg at low engine rpm (under 2000), or if that is normal.

 

[allmyEXes]

It could be a faulty PCM issue. Is that a 4.0 SOHC ?

 

[974X4BLACKSPORT]

I run 89 in my 97 OHV 4.0, runs much better on 89 than 87, with 130k miles, I imagine carbon build up in the combustion chamber and on top of the piston is raising compression past what the factory calibration can handle for 87 octane fuel, so I jsut run 89, it is very happy with that.

 

[Tell1999]

I did more checking with the scanner. The spark advance stays ok until I put the transmission in drive, then it goes up to 34 degrees at 1200 rpm and starts pinging. Would anyone know where to look for the problem?
Thanks in advance

 

[Tell1999]

It could be a faulty PCM issue. Is that a 4.0 SOHC ?

I believe it is. How would a guy check a PCM?

 

[Tell1999]

I run 89 in my 97 OHV 4.0, runs much better on 89 than 87, with 130k miles, I imagine carbon build up in the combustion chamber and on top of the piston is raising compression past what the factory calibration can handle for 87 octane fuel, so I jsut run 89, it is very happy with that.

I tried adding a octane booster, was still pinging.

 

[imp]

I tried adding a octane booster, was still pinging.

@Tell1999
Unless I'm mistaken, that eng. has a Knock Sensor, which is there to prevent pinging. Could be it's faulty. Not sure about 1999, but it's clearly shown in my Ford Wiring Diagrams for 2004 Explorer, 4.0 SOHC.

We can't look at the advance scheduling programmed into the PCM. They take into consideration many factors. Only way to "test" the PCM in your case would be to substitute another known good one. imp

 

[974X4BLACKSPORT]

I tried adding a octane booster, was still pinging.

So then,, what was the net result octane rating of the fuel you where using after adding your octane booster?