Need help, have ping at hot idle only

94rang · Jan 31, 2017

Hi guys, im new to ranger station. I have a 1994 ranger 3.0L manual 4x4. I currently have a pinging noise at hot idle. I have searched rangerstation and only to find pings happening under heavy load. My ping happens at idle and only at idle. Alittle background info, I bought the ranger with a blown 3.0 (main and rod bearning spun), so i installed a junkyard 3.0 from a Taurus. Yes, I installed ranger headgaskets, and everything from the ranger. I did not install new thermostat, water pump, wires, coil, pick-up on distributor, old fuel filter.I used old but not fouled plugs. Now, I know i need to replace them anyways, but im really tight on money, and the truck doesnt overheat according to the gauge, or missfire. Any ideas where to start cheaply?

RonD · Jan 31, 2017

Welcome to TRS

Try a can of Seafoam in the gas tank, that will clean dirty injector tips.

Guessing from your description that at idle a cylinder, or two, is getting a Lean mix so it is pre-detonating/pinging because of that.

Computer normally runs a Rich mix at idle to prevent this, and at idle computer doesn't use O2 sensor so can't tell if a bank is Lean

Fuel injector tips SPRAY out fuel, but as time goes by they can get a bit dirty, and at idle fuel DRIPS out, lol, so not as good a mix with the air and you get Lean air:fuel mix
At higher RPM air flow is faster and injectors are pumping out more fuel faster so not as noticeable, and of course O2 sensors are being used so computer can increase fuel if Lean burn is seen.

The 3.0l runs a slightly higher compression(9.3:1) than say the 4.0l(9.0:1) so is actually more prone to pinging on Regular gasoline(87 octane), but as you said that is usually under load and usually caused by partially clogged EGR valve/tube or carbon build up in the cylinders, another thing the 3.0l is known for.

cbxer55 · Jan 31, 2017

The above poster fails to realize how the injectors work. They spray the same amount of fuel every time they squirt. All the computer does is alter how often they squirt. It's a healthy squirt every single time, no dripping. But as RPM or throttle position change, they just squirt more often.

All the injectors squirt at the same time, every time. And the pool of fuel is just sitting at the intake valve waiting for it to open.

Maybe the one's earlier than my 98 work in the manner posted above?????????????

Never heard of a vehicle pinging at idle. That's a new one to this old guy.

94rang · Feb 1, 2017

It only happens when the ranger has been idling for quite some time. I dont currently have it tagged at the monent so, i let it idle for a while. But before this ranger, ive never heard of pinging at idle. Ill let it idle for about 20mins and right around the 18min mark it starts to ping. It only sounds like its coming from the passenger side bank.

Thank you for the advice though.

RonD · Feb 1, 2017

Some Throttle body fuel injection would work similar to a carb system and keep air:fuel mix in the intake for any cylinder to pull in, but not systems that have an injector at each cylinders intake valve.

These do use injectors that computer controls the "Open time" on.
0 milliseconds to say 30milliseconds(ms)

At idle an injector might be opened 5ms, at 2,000rpm 15ms, ect.......
Computer knows(is programmed for) the fuel pressure and the injectors flow per MS at that pressure
Computer knows the engine displacement, i.e. 3 Liters, and so can calculate the air used at at any RPM and throttle position
It uses a MAF sensor to fine tune that air flow for altitude and temp(along with IAT)

That calculation sets 0 Short Term Fuel Trim(STFT) and computer opens injectors for the calculated milliseconds
Computer then gets the O2 sensor data on the burning of that amount of fuel
If O2 shows Lean then computer sets +2 STFT, and opens injectors longer
If O2 shows Rich then computer sets -2 STFT and opens injectors a shorter time

At idle cylinders will tend to heat up unless mix is a little Richer

In the old carb days engines could "diesel" or "run-on" after key was shut off, this was caused by hot spots in the cylinders.
When spark was shut off and RPMs slowed gasoline could still be pulled from the carb into the cylinders, these hot spots would ignite it, which makes those hot spots even hotter, lol, so you got run-on
Can't happen with fuel injection because spark AND FUEL is cut off

But you can still get the hot spots at idle
Since the heads were removed and I assume cleaned of carbon build up and piston tops as well, I can only suspect Lean condition at idle causing the pinging.

One thing I forgot to ask is what is your idle RPM full warmed up?
Manual trans should be 650
Automatic 750

94rang · Feb 1, 2017

To be honest, i dont know. And im currently away from my truck till this weekend. This weekend i can check hot idle RPM's and let ya know. And yes, i cleaned the heads and pistion tops.

94rang · Feb 11, 2017

Sorry about that guys. My truck is idling right around 600-650. And I was mistake, its not a ping, its a POP. After the truck has been idling for a little bit it POPS, then you can shut the engine down and it POPS a couple of times then it stops.

Thermostat is stuck open, water pump is at least 3yrs old. Hope that helps out a little

RonD · Feb 11, 2017

POP is a back fire, you have a cylinder that is misfiring, when a cylinder doesn't burn the air/fuel mix it is dumped into the HOT exhaust system, where it will ignite with a POP.

Thermostat is stuck, when they fail they are suppose to fail open so engine doesn't over heat, but that doesn't mean they are FULLY open, so "stuck open" is a good way to fail but it doesn't mean engine won't start to get hot.

Ford temp gauges have about 210degF as the center
Engines should run at about 190-195degF, if using correct 192deg Thermostat
So gauge should show just below 1/2 when fully warmed up
When climbing a long grade temp will climb up to just above 1/2, about 220degf

If your temp gauge is below 1/2 when driving but climbs up a bit when idling then your Fan Clutch is failing.

Need help, have ping at hot idle only

94rang

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cbxer55

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