Spark Plug Gap

[sjjones]

94 - 4L OHC. Books calls from between .052 to .056 spark plug gap. I'm using Autolite plubs and gapped at .054

I was experiencing ping before I recently changed plugs and still have it with the new plugs. No noticable difference.

Question: If a person is experiencing ping, would it make any difference if the plugs were gapped closer to the extreme .052 or .056 gap? Just wondering if changing the gap either direction would help the ping. Many thanks.

 

[Rhett]

I have experimented with gap for years. And gap did not affect pinging behavior...and I did try to change gap to combat a ping. I have gapped 0.52" , 0.54" (spec), all the way up to 0.65. With these engines, I HIGHLY suggest using Motorcraft platinum plugs. (AWSF-PP?).

Gap seemed to have no effect on pinging.

 

[fastcougar]

Spark plug gap will NEVER have an effect on pinging ... good, bad or indifferent. Pinging is caused by uncontrolled detonation BEFORE spark OR multiple flame fronts during/after spark ... uncontrolled being the key word. This is usually caused by low ocatane gas or a lean mixture. Ensure that you have no leaks in your intake as this would allow unmetered air in and lean out the mixture. Another very common cause is carbon buildup within the cylinder, which causes a "hot spot" to form ... the only way to confirm this is with a Borescope or to remove the heads. Finally, another cause is misinformation via sensors to the ECU, resulting in an inadvertant lean mixture. I would suggest doing a full tuneup, to include cleaning the MAF and replacing any O2 sensors that have more than 30K miles on them.

Have you tried going up a grade in gas to see if the ping goes away?

 

[sjjones]

Spark Gap - Pinging - Update

Many thanks to you folks for setting me straight on the spark plug gap. Makes sense - just wanted to make sure. I will say that, except for the occasional and annoying ping, my truck idles vibration free and seems to have as much punch as it ever did. Actually, with 125,000 it runs pretty darn good.

In regards to my pinging, see my post below. I've cleaned the MAF numerous times - its so dog gone easy I enjoy it. I've change out plugs and air filter. Neither actually needed it, but just like to start off fresh. My No. 5 plug had some light color crust on it which indicates a leaking lower manifold I'm told. Tried retorquing the bolts to specs with no help. I have been losing a "very little bit" of coolant since I got the vehicle in 96, but has never got worse.

I've got a few other things to test/check first, but I may actually replace the gasket. I got all the tools in the world, but not the confidence to replace the lower manifold gasket - so will have to pay for that one. First, I'll exhaust all other simpler things you folks suggest I check.

I haven't replaced the O2 sensors since the car was new. Should I test them or just replace them? Is replacing them a tough job? Many thanks.

 

[fastcougar]

except for the occasional and annoying ping, my truck idles vibration free and seems to have as much punch as it ever did

Is it a miss/stumble at idle or a ping when driving ... something you said made me question if it's a ping.

With 125K miles on the clock, I would just replace the O2's regardless ... you gas mileage will increase ... Bosch actually recommends changing your O2's every 20K miles (go figure, they make them) ... I would take that advice with a very large grain of salt. I replace mine every 40-60K. I monitor my gas milage with every fillup to help me determine if it's time to replace them. They are very easy to change yourself.

 

[sjjones]

Ping

Cougar,

Car runs and idles as smooth as new. Got ping at times, usually when its in a higher gear, rpm down, and then excelerate. From a stop with foot on the floor - truck has great pickup with no ping.