Having a pre-detonation problem with my daily driver. It is a '94 E-250 with a 5.8l. This vehicle has been maintained well. there are no modifications. In the past month a ping has developed at highway speeds climbing even the smallest hill. First I checked the basics, pulled codes and ran a full sun engine diagnostic to check the basics and verify my recent full tune-up (plugs, wires, cap/rotor, pcv, fuel filter, air filter) had nothing to do with it. Runs cool as ever, no oil usage at 136k miles, gas mileage has not changed. Sun analysis gave a clean bill of health. Had codes 332 and I think 311, both emissions related, Low EGR flow and no AIR injection on one bank. Found a vacuum line rubbed partially through that supplies those systems. Repaired it, verified vac and tested again. The AIR code went away but the EGR persisted. Narrowed down to the EVR wasn't sending enough vacuum the EGR valve. Replaced the EVR. Thought the problem was solved because all trouble codes are gone. STILL PINGS.

Next I verified fuel pressure, fuel pressure regulator, and even scoped the map sensor. All check out. Adding to the problem is the EEC IV computer, it is VERY STUPID. It is a speed density system without live data or a knock sensor. This thing knocks bad and there are no trouble codes. I need to figure out what is up before I burn a valve or hole a piston.

My next theory is a Injector laying down. Without a way to get live data from this thing (inj pulse width, o2 sensor output, map sensor data) I am running out of options in terms a testing.

Anyone have any experience with this sort of problem, Ideas????

 

Basic question- is your timing at 10BTDC? I bought my truck used and it pinged pretty bad. After doing all the tune up stuff, I found that the timing was around 13-14, so I backed it down to 10 and she does not ping with 87 octane now.

Good luck.

 

Have your fuel injectors cleaned.

 

Timing is a 8 deg BTDC at idle, SPOUT unplugged. Considering the ping I decided not to adjust to 10 deg. The Engine Analysis also looked at timing advance by checking at 1500 and 2500 RPM, well within spec at both RPM. I have cleaned the fuel injectors/top cylinders twice with the type of system that connects to the fuel rail and runs the truck for ten minutes with the fuel pump disconnected, no change.

I have noticed that since the weather has cooled off, the problem has become more intermittant and happens only after driving 20+ minutes. it is starting to look more like an electrical connection or some other electrical glitch. Though I have checked fuel pressure in the shop four times now perhaps the fuel pump is not maintaining pressure due to age and heat in the fuel system. Or, maybe it is an ECU problem with either the injector driver or ignition control? I may figure out a way to hook up my FP gauge so that I can drive it long enough ping while monitoring the fuel pressure.

 

Bad EGR valve? Opening too much leaning it out?

 

I have a couple of questions about this hypothysis. First, have you had this happen before? I have never had a vacuum diaphram actuated EGR open too far, usually they coke up with carbon or the diaphram fails and they don't open at all or not enough.

Second, I am not very well versed in the operating strategy of the EEC IV system, I know it is speed density, batchfire, ignition and trans control built in. It is also pre OBDII, and doesn't seem too concerned with monitoring systems for otimum performance. The reason I say this is that there is a EGR position sensor on top of the diaphram. it is what alerted me to the EGR problem originally (not opening enough). Fixing the vacuum leaks cured that (as far as the ECM is concerned). Are the operating parameters so wide for EGR pintle position that this failure could happen without a code being set?

Lastly, I know the reason for EGR as an emission control is to introduce an inert gas (in this case, exhaust) into the combustion process to lower combustion temperature and consequently the formation of oxides of Nitrogen (I think that is the poluting gas in question???) Lower combustion temperatures should reduce pre-detonation. And while I agree that a lean condition would cause higher combustion chamber temperatures and possibly a ping. I am under the impression that exhaust should be relatively inert, especially in a lean running engine and excessive recirulation theoretically should not affect the air fuel ratio, only reduce the quantity.

Please let me know if I am missing something.

 

I never understood how putting HOT exhaust into the combustion chamber would cool the mixture. I have seen the EGR make plenty of engines run lean and ping.
The only other thing that I can think of is alot of carbon built up in the combustion chambers causing hot spots to make it ping.
Jimmy

 

Could definitely be caused by a carbon build-up. I have talked to specialty Ford repair shop owners that say that for some reason Fords are prone to this problem and it can cause all sorts of strange driveability problems. Having done the top cylinder/injector clean process twice along with adding BG's 44K twice and trying The Chevron Techron additive I would think that this possibilty should be all but eliminated. Unfortunately, there is no easy way to tell if my efforts have worked since the ping persists.

Since my last post I let the truck idle for about 20 minutes and measured the temperature of the heads at spots directly over each exhaust port with a laser thermometer. All cylinders were within 10-15 degrees F except #3 that was about 50 degrees higher. I'm thinking clogged injector. I am going to pull them all and have them bench tested/ultrasonic cleaned/retested. it would only take one lean cylinder to make a ping. In would also add that I did verify that #3 injector is firing using my mechanics stethoscope. Clickity-click just like the rest. I would have checked the electrical connection but it is trapped under the upper intake manifold.

Lxman1, the following is not directed at you or your comments, it is only in response to so many troubling posts I have read at this site since I found it.

I think emissions systems are far to mis-understood. While not a tree-hugger by any stretch of the imagination, I am into the idea of responsibility and sustainability. Most modern emission systems do not significantly impede the production of power. I have read too may posts about disabling EGR systems and "gutting" catalytic converters in the name of more performance. The fact is, unless you are racing the 1/4 mile and thounsandths of a second count, those systems have very little negative effect on performance when they are working as intended. By far, the better performance gains are made on the intake side of the engine. The notable exceptions to the idea that intake is better for modification is tubular exhaust headers and properly placed "H" pipes in aftermarket dual systems. "True Dual Exhaust" treats the V8 engine like two independant 4 cylinders and ignores the performance gain that properly scavenged exhaust can provide. These mods can be done without disabling emission systems!!

On the intake side, more improvement can be made. One of the primary considerations for automotive design engineers when designing air filter assemblies is to minimize interior noise levels. Many of the aftermarket filter set-ups, especially the cold-air style are a good place to start. Since most newer EFI systems are mass-air based this can be performed with no other modifications. We all know that our engines are essentially air pumps, and more flow should mean more power, right? It is far easier to get rid of the spent combustion gasses than it is to pack them into the combustion chamber. This is one of the reasons exhaust valves/ports are so much smaller than the intake. For those that are interested, there are some excellent books on this subject. One is: Four-Stroke Performance Tuning by A. Graham Bell, written in laymans terms it is very easy to read and apply. Another is: The Scientific Design of Intake & Exhaust Systems by Philip H. Smith/John C. Morrison, this one is far more "heady", and though very authoritative, it is a difficult read without an engineering background.

As for the EGR system, the operative words when describing the function of this system are "inert gas". When this system was in development for the reduction of dangerous pollutants, other inert gasses were used (perhaps Argon). I am not a chemical engineer but I have read that this system does, through the use of this inert gas, lower the combustion temperatures preventing a specific chemical change to one of the polluting component gasses that can only happen at extremely high temperatures. Though I don't understand it intimately, I remember that the source I read it from was quite solid (maybe an ASE study guide). It was also noticed that in a properly tuned engine, exhaust is relatively inert, meaning that there is nothing left in it to react in the combustion process. This made exhaust the logical choice as an inert gas source. With the very small quantity that is reintroduced by the EGR, temperature of that gas is of little consequence to function. The effect of lowering overall combustion temperature with this system outweighs the very small intake temp increase.

With this in mind I might argue that pinging is more likely caused by a failed EGR for reasons outlined above, and not because EGR leans the air/fuel ratio.

Please understand I do not wish to appear a know-it-all, I only enjoy the pursuit of higher truth and understanding. Online forums are a great place for the free exchange of ideas, but everyone should remember: you can't believe everything you read. Education should be a lifelong endevor.

Happy wrenching!!

 

Okie Dax,

I am brand new to this forum. I have spent many years on the early model BMW forums. I have never had a reason to seek out a Bronco forum until now. I am very relieved to have found you on this board.

I have had a ping delvelop(out of the blue) in my engine(5.8l) under load on a grade. The engine begins to miss, ping intemittingly and loose power. Otherwise, it starts perfectly, idles steady and runs perfect under normal conditions. I changed the spark plugs, plug wires, cap, rotor, fuel filter and O2 sensor. It still pinged. Ok..Sensor problem.

I took it to a local Ford dealership so they could pull the codes. Took it for a test drive with the mechanic, recreated the problem. They performed the diagnosic - No codes...Everything was normal and timing was perfect. They told me it was a normal running condition. I told them they were out of their minds. SO, with no codes, I decided to have them change the Throttle Plate Sensor(dumb shot it the dark) $400 dollars later..IT STILL PINGS!

Now I am on my own. I am going to change the Fuel Pressure Regulator, but I suspect that it is a fuel injector as well. I have run injector cleaner(for a couple of weeks) and still IT PINGS!
SO, keep me posted as to your solution to your problem.

Truck Stats: 1994 Bronco 5.8 EFI, 4EOD, 128,000 freeway miles

Thanks
T. Snyder

 

Welcome T. Snyder. I am new here myself.
It is a sad state of affairs, but a common one. I think the thought pattern is this "if I can't figure it out, there must be nothing wrong". Normal running condition? Why didn't the truck ping for the first nine years of its life?

Ford does a lot of things right but the pre OBD II computers were dumb as a box of rocks. If our trucks were one or two years newer we might have something in the way of self diagnostic info to work with.

Yours may be different but I thought fuel pressure regulator as well. I installed a fuel pressure test gauge and applied vacuum to my regulator with a hand pump, mine worked as intended, 42-43 psi no vacuum, drop of about 10 psi at 20 inches of vac. I ruled it out. I am down to two things, either the clogged injector (chem cleaner helps but does not make like new) or an intermittant ECM problem relating to either timing curve or injector pulse "drop out". I don't want to replace the ECM again (burned the EPC solenoid driver an couple of years ago). I have had the ultrasonic injector cleaning procedure cure my customers Fords in the past. The deposits that clog them over time are like stone! The thing I really like is getting the before and after data. Just have to make sure to number the injectors when removing so that you know which ones were the problem.

I am too busy with work right now, I don't know when I will get a chance to pull the injectors but I will post the outcome.

 

Dax, No insults taken.
I tend to agree with your injector theory. It may not clogged, but it could just have a weak coil the will not open it up completely when the extra fuel is needed. Unfortuately, You will have to remove the upper intake to get to it.
Good luck and let me know what you find out.
Jimmy

 

pull egr value from intake. pulum . check passage round hole it will be pluged with carbon. i have a 93 f150 5.o. pinning when it shifted in to 3rd gear i replaced temp sensor map pimp in disdr all with no help. truck ran good just pinning. my motor manual told me to check this out was pluged solid i cleaned it out . now ping is gone. HOPE THIS HELPS

 

Truck was running terrible ruff idle no power ( F 150 5.8 ) 91
went to shop. found EGR has vac at idle screwed everything up
plugged vac line truck runs fine. Mech said to change oil in case was conaminated by such a rich mix .Question why is there vac at idle . What do I check
Thanks

AL

 

The vacuum solenoid for the EGR could be stuck open, this would cause it to have vac all of the time.
Jimmy

 

I know it's a slow and time consuming process, but try using a break-out box to do an injector balance test. If the rpm doesn't drop enough, you have found a bad injector.