'94 4.0L pinging continues to baffle me. I have read the pinging threads and am systematically (balance of cost and liklihood) replacing parts. I just finished the O2 sensor and plugs. I have cleaned as recommended the MAF. Idle is OK, so the IAP doesn't seem to be the culprit. No, I haven't begun the vacuum journey, but that will be soon. So far, most of the pinging has disappeared, but I noticed that on warmer days the pinging is worse and the cooler days the pinging seems to be non-existent. Is my observation that I may be addressing the pinging situation based on the parts I have replaced/repaired so far, or based on the fact that the weather is getting cooler? If cooler ambient air seems to resolve the pinging issue, does that suggest I really should buy a new MAF? What is the science behind all of this? Thanks.

Michael

 

Deteriorated plug wires are by far the most common cause of ping on these engines. The "science" is related to the carbon/graphite core of the plug wire. Time, vibration, heat/cold contraction all produce micro cracks. Each tiny crack increases resistance along the wire until, accumulatively, a weak spark results at the plug. This, in turn, causes poor/delayed detonation in the combustion chamber and a "rattle or ping" noise. Each plug wire has a resistance range. You can test the wires and see if any fall out of range. Somewhere, perhaps the Ranger forum, is a list of resistance values.

In your case, the colder weather may contract the plug wire just slightly allowing less resistance and better firing chacteristics. Of course, once the underhood temperatures rise to operating range, you should also notice more pinging. If this is not the case, the problem may lie elsewhere.

 

firs of all check wires and spark plugs, rotoк and cap.... use wires spray to let them work well when they are wet....

 

ouh, your aero may have DIS ignition, so no cap and rotor... well, chek wires and plugs

 

I would try cleaning the MAF once more. It took me a couple tries but it cleared up the same exact symptoms you describe. I can run 87 octane gas again too!

http://www.autoshop101.com/forms/h34.pdf
http://www.autoshop101.com/forms/h32.pdf

 

remove the MAF cartridge from the MAF body as VanGo did with Torx bit.
soak for at least 1/2 hour in carb cleaner, nothing stronger. part of the cartridge is plastic and melts in some strong solvents. the elements are fragile, fine wire wrapped on thin glass rod

examine with magnifying glass, elements should be perfectly clean with no black crud.

any codes? defective intermittent MAF should throw a code occ.

next is the great vacuum hunt. not fun. spent days on mine, ended up replacing most of the vac. hose. use a high grade neoprene, even better is Viton or silicone. Ford used the cheap stuff.

the vac. tree mess and the vapor canister plumbing under the air cleaner are two major culprits

 

Michael,

I forgot where the original thread to this was, but did you ever check the plugs to see how they look?

 

Also, non-EO plugs can cause pinging. More plugs are not in the right heat range, so the tips of the plugs get way too hot. This is also why those types of plugs do not last very long either.

And as for pinging worse in warm weather, that actually points more towards vacuum or intake leaks.

 

Look carefully to plug info. Not every spark plug that fits head phisically works really well....

 

Does this pinging dissappear with higher Octane gas?

Cooler ambient air is denser & causes the computer to compensate with increased injector pulse width. In effect a slightly "richer mixture" capable of producing slighty greater power output from the engine. Ever noticed how your fuel consumption increases in the winter? it's largely due to density of air & resulting fuel compensation.

Does your engine have a distributer with an octane rod ?

You can check for indication of carbon build up in the combustion chambers with a compression test. Run some b12 decarbon cleaner into the engine might help.

Over advanced timing & lean running fuel ratio could be culprits. Does fuel rail pressure come close to specs ?

 

what brand of plugs and part # of plugs?

what grade of gas used in the past? over time, 89 and higher octane fuels cause carbon buildup due to a cooler flame front and incomplete combustion in normal range compression engines such as the Ford 4L. Ford has a TSB Warning on reg. gas ONLY

i decarbon my 4L every 30>40k using technique mostly following the Ford TSB
https://www.ford-trucks.com/forums/7...ning-4-0l.html
using at least 2 can of Berryman B12 which is similar ingredients to the Ford overly expensive carbon solvent. the soak is critical, don't try and rush the job.
i start the decarboning with a water mist steam cleaning douche. 1/2 qt of water sucked in thru an 1/8" tube thru the throttle body plate hole or plate gap.
then the TSB decarbon soak.

carbon buildup in the combustion chamber not only raises compression, but it heats up to red or white hot in pinpoint locations supplying another ignition point source prior to correct timing firing point on crank rotation.

pinging over time can crack heads and pistons, bend rods, damage crank shafts.

the stoichiometric mixture of 14.7:1 that a properly operating OBD system runs in modes warm idle, warm cruise and warm partial acceleration is calculated based upon air and fuel weight, not volume which is affected by temperature. the ECU/PCM measures intake air temps and the tables extrapolate a corresponding approx fuel temp. the ECU assumes a normal O2 content of the air. the O2 sensor brings the system into balance by measuring unburned O2 in the exhaust. too much fuel=no O2 in exhaust too much air i.e. oxygen=too much O2 in exhaust. the O2 sensor forces the ECU to track back and forth across the stoichiometric mixture point since conditions constantly change and no system can lock and hold one setting.

winter cold temps increase fuel consumption because of longer open loop rich air:fuel mix ECU run times till closed loop operation kicks in, increased gear drag due to thicker viscosity lubes and oils and lower energy fuel. alcohol is made to drink, not put in the gas tank of an engine designed for 87 octane gasoline.