Hello! and need help with engine "ping"

[Mark2378A]

Thanks for the "welcome". I am amazed at the knowledge base of this site so I thought I'd seek some advice. I have searched the site but was unable to find a similar thread. I own year 2000 L #2378. I purchased it new in May '00 and have not modified it in any way. The SEL came on lit up Dec. 24th. I took it to the dealer to check out and was told a code for the MAF sensor was stored in memory. The tech told me the MAF was reading voltage a bit higher than standard and suggested replacement. Immediately after replacement, the enginge developed a "ping" at low RPM under light load (traveling up a grade in 4th gear-1,500rpm, at 50-55 mph). Took it back to the dealer where everything checked out o.k. I did have them replace three items that were old/worn and may have been letting in unmetered air. After three more trips to the dealer, they are still scratching their heads. Gas was ruled out, as I had the fuel at the only station I purchase fuel from tested by Weights & Measures (91.4 Octane was the result) and have since burned through another half tank of fuel from another station. The dealer tells me they have run every test possible and no codes are showing. My gut says the MAF (P#XL3F 12B579 AA) is the issue, but they insist it checks out fine. Any ideas (besides to find another dealer)?

[Mark2378A]

Update: Changed out the MAF sensor, replaced the fuel, fuel pressure checks out ok, but the ping remains. Is anyone aware of problems with re-manufactured MAF's?

Update: Now told the problem is the intercooler coolant pump. Coolant temp is too high at 160 degrees. Anyone have an idea of how long a skilled mechanic would take to change one out?

Update: New intercooler coolant pump solved the problem. IAT#2 went from 160º to 105º (max reading should be 120º). Check e-bay & buyfordracing.com ($89) and Fordracing.com ($145). If the dealer is asking $300, it is because they are not in the Ford Racing program. Ask about warranty when you are checking prices.