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There has been a lot of discussion on this and other Ford sites about the Mass Air Flow Sensor (MAF) getting dirty and causing driveability concerns. One particular question that gets asked a lot is whether or not a dirty/faulty MAF can cause or contribute to the dreaded engine knock or "pinging" that we have all heard so much about. Apparantly, Ford determined several years ago that yes, a dirty MAF can indeed be a source of pinging.
This is an excerpt from a 1998 Ford TSB:
Mass Air Flow (MAF)- Sensor Contamination- Service Tip
MASS AIR FLOW (MAF) DISCUSSION
MAF sensors can get contaminated from a variety of sources: dirt, oil, silicon, spider webs, potting compound from the sensor itself, etc. When a MAF sensor gets contaminated, it skews the transfer function such that the sensor over-estimates air flow at idle (causes the fuel system to go rich) and under-estimates air flow at high air flows (causes fuel system to go lean). This means Long Term Fuel Trims will learn lean (negative) corrections at idle and learn rich (positive) corrections at higher air flows.
If vehicle is driven at Wide Open Throttle (WOT) or high loads, the fuel system normally goes open loop rich to provide maximum power. If the MAF sensor is contaminated, the fuel system will actually be lean because of under-estimated air flow. During open loop fuel operation, the vehicle applies Long Term Fuel Trim corrections that have been learned during closed loop operation. These corrections are often lean corrections learned at lower air flows. This combination of under-estimated air flow and lean fuel trim corrections can result in spark knock/detonation and lack of power concerns at WOT and high loads.
One of the indicators for diagnosing this condition is barometric pressure. Barometric pressure (BARO) is inferred by the Powertrain Control Module (PCM) software at part throttle and WOT (there is no actual BARO sensor on MAF-equipped vehicles, except for the 3.8L Supercharged engine). At high air flows, a contaminated MAF sensor will under-estimate air flow coming into the engine, hence the PCM infers that the vehicle is operating at a higher altitude. The BARO reading is stored in Keep Alive Memory (KAM) after it is updated. Other indicators are Long Term Fuel Trim and MAF voltage at idle.
You know, there are so many things that can cause pinging. The truth is, the timing on our 3.0's has been set to a level that puts it at the very edge of pinging even under perfect circumstances. Where this leaves us is having a good engine that Ford has tried to tweak for max performance and minimal emissions.
I believe that with good TLC and proper maintenance, the Vulcan will run forever. Its just more important to keep em tuned than on some other engines. The positive is, that this annoying ping kind of alerts us that we need to perform some routine maintenance where other engines, also needing the same maintenance, don't let the driver know until it becomes a huge issue. Now I know this is not the intention of the designers, its just a more positive spin on tghe old pinging problem.
If you think about it, the pinging has probably made most people (at least on the forum) perform maintenance that they would hav e not performed if the pinging never occured).
I posted before that I added ethanol as an additive for a few tanks to stop pinging, it worked and I have now ran 3 tanks with straight 87 (no ethanol) from Amoco and have no pinging. I believe that the ethanol clkeaned my fuel system anbd probably got rid of some carbon buildup. My guess is that I will have to do it again every few months but I have no problem with that.
Anyway, maybe we should all hold hands and sing coom-by-ya and thank the Ford engineers for our little "maintenance reminder alarms".
Excellent points regarding the Vulcan, JB. I think your comments can be applied to the Ford 2.9-4.0L motor as well .... both the 3.0L and 4.0L engines have been tweaked and bored and everything else in order to get the most out of them. And they have both been in service for over a decade so obviously there has been plenty of time for Ford to squeeze as much as they could out of them.
As far as singing coom-by-ya and thanking the Ford engineers, I'll pass on that, thanks. Just give them my regards.
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