I've got a '84 Merc Grand Marquis w/ 302 CFI, AOD, 77K (original!). It pings loudly at low RPM under load (i.e. going up hills). A tank of premium didn't seem to help. Under slightly more load (i.e. with many passengers going up hills) it will 'jerk'. I can't tell if it's the motor missing or tranny (torque converter?) since I've no tach. On downshift when the revs go up, both problems stop.
Is the pinging a timing issue or something else? Any ideas what the 'jerk' is? Much thanks in advance.
Make sure the #7 & 8 spark plug wires are not routed too closely. They can cause a crossfire which sounds like a very bad ping and WILL destroy an engine if not corrected. Ford had a TSB out explaining this. Bob
"Bob" wrote in news: snipped-for-privacy@corp.supernews.com:
If it's not the plug wires (it wasn't on my '83 which had exactly the same symptoms) it may be the TFI module giving trouble. Mine progressed from the symptoms you describe to occassional stalls when the engine just would not refire until it cooled a bit.
Nice ride! I have the exact same year and engine....
Mine was VERY bad at pinging. My trouble was serious carbon buildup in the combustion chambers. I used the water trick (run a small stream of water down the intake with it running and rev until it clears up).
I did this for a few minutes, and it left a PILE of carbon under the exhaust pipe. I actually shifted it around with my finger because I couldn't believe it!
As for the bucking..... You should unwrap and check out the wire harness that runs right between the windshield wiper motor and the hood. I found a huge splice in that exact spot. But the insulation had worn off of the splice, and it was causing the poor ol' girl to buck like mad.
Scanning the computer pulled pretty much EVERY code possible (which made me feel really lost).
Isolate and tape off wires in that harness (remember, a bonch of them are actually supposed to be spliced together there, but you can tell they are supposed to be together.)
Since I taped off the wires in that location, my baby has been running perfectly.
But the ping is likely carbon buildup, or possibly a malfunction of the egr valve.
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