Mechanics

ENGINE PINGING

1984 Ford F-150 • 6 cylinder 4WD Manual • 99,000 miles

1984 ford f150 4.9 litre engine pings under load. Timing set to 10 degrees BTC. Does not seem to advance (or increase) the spark when going up hill. Otherwise, runs well
Avatar
Ukeboy
August 3, 2011.



Does DIST have a vacuum diaphram?


Docfixit
Aug 3, 2011.
No it doesn't. It has the EEEC 4 distributor with the ignition module attached to the distributor. 84 was the first year for this. I wish it had a vacuum diaphram.

Somehow, the computer is supposed to advance the spark?


Tiny
Ukeboy
Aug 3, 2011.
Then it is TFI and they can be a head ache. Remove on side DIST take to parts store have tested.


Docfixit
Aug 3, 2011.
Does the module on the side of the distributor control the advance? Or is spark advance controlled by the ECM? Any other solutions to advancing the spark? Probably not linked to carburation.

Again, Thanks for the reply


Tiny
Ukeboy
Aug 4, 2011.
TFI interfaces with ECM to advance and TFI modules plagued with failures


Docfixit
Aug 4, 2011.
It should have a omputer bypass that has to be removed in order to set timing. If this is in when timing the engine it wont be right.


Tiny
Bigjim79
Aug 5, 2011.
It does have the bypass. It is a single black wire plug you disconnect next to the module. The process is to unplug, set it at 10dg advance, plug it back in and the engine idle speed increases. The timing is then about 13 df BTC. I hear that these run between 13 and 15 df BTC after set at 10 with cpu bypass wire off.

I am beginning to think it is not timing. Might be better to look at the EGR system. Possible carbon build-up in the head.

It runs very strong and accelerates well. Only at about 55 - 60 mph on a hill does the pinging occur.

Tires are 31x10x15 which are oversized. Hard to believe that it is over "tired" so to speak.

All help is greatly appreciated.


Tiny
Ukeboy
Aug 5, 2011.
Thing got centrifugal advance, down inside the distributor?

If a spring is broke, weights are thrown out 100% of the time

Stays at max mechanical advance

Upon checking the timing, it appears timing is too high

You compensate by moving the distributor to make it right

Now, all you have is Computer Advance (Vacuum advance, with my Older Jeeps)

Really, Now. At idle, timing is right, as engine speed increases. There is no "Mechanical Advance". Computer advance cannot make up for "lost" mechanical advance

May not be the case with yours---Happened with my Jeep, several times with the Prestolite distributors I once ran--I upgraded to newer Motorcraft used in '79 on up, for this and other substandard attributes of the original distributor

Regardless. It was a good story, anyway, wasn't it?

The Medic


Tiny
CJ MEDEVAC
Aug 5, 2011.
There are no moving parts in the distributor other than the stator. No springs etc. All computer generated. I would change the distributor to a more conventional vacuum or mechanical advance, but I doubt that the computer would find it.

Ford wants the distributor at 10 dg btc with cpu bypass. That way, when plugged back in. You get the 13 dg.

Wish it was all that easy. And yes, I liked your story.


Tiny
Ukeboy
Aug 5, 2011.
Plugged back in, watching the timing marks w/ gun----does it climb on up as RPM increases?

I don't know. Are there specs as to what advance should be a certain RPMs?

Got 2 more things to offer--one is check really good for vacuum leaks. Won't hurt anyway, should do it periodically, just to stay on top of things!

And 2nd

GET REAL JEEP BE HAPPY!

Ex. Of Reliability--CJ 5 made '55-'83, CJ 7 made '76-'86----see their forums, # of questions, vs: this new stuff!

Mr. Jeep is 35, Willy is 65. Jeep. Name alone, speaks volumes!

I hope you get this figgered out, trade in valve might be higher!

Good Luck.I'm still watching this, don't let me down!

The Medic


Tiny
CJ MEDEVAC
Aug 5, 2011.
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