No April Fools on this one guys and gals - this one is for real. I have
finally solved my pinging problem. Not sure if this will help others
but this is how it played out... I was doing some brainstorming before
sleeping last night - this pinging problem keeps me up at night. I
starting listing out in my head every possible thing that normally
causes pinging. I love the KISS principle but I never seem to be able
to follow it 8-). Timing - advanced timing - yep, when I use the
performance computer - sure enough my pinging gets much worse. This was
my biggest hint and I didn't even dive into it until now (10k+ miles
later). On our trucks - timing is controlled how? Entirely by the PCM
- I've said that many times. Timing is a PCM output - to get this
output, what inputs are considered? For the most part that would be rpm
and load. rpm and load - rpm and load - rpm and load. Ok next step -
must check out these inputs for validity. Load is measured how - hmmm -
that would be the MAP sensor (the basis for our fuel injection system) -
wow - thats a pretty important sensor huh. Wonder what the specs on it
are? <digging through manuals> Bingo - diag procedures say read voltages
with key in the on position - should be 4.5 to 5.5 volts. More diag
stuff that I'll read later. Will check it in the morning...
Fast forward to this morning - digital volt meter in hand. KISS - I
know how the MAP sensor should act - skip reading the rest of the diag
procedure. Blip the throttle and it should change right? Its reading
Manifold Absolute Pressure anyway - more throttle - more difference in
the reading... Wheres my truck....Reading voltage on MAP sensor - 3.0V
hmmm - ok rig volt meter so I can start truck and watch voltage while
working throttle. 3.0V hmmm - blip throttle - 3.0V hmmm - nail throttle
to floor (WOT) - 2.99V hmmm. MAP seems to not be responding very well
(understatement). Ok - it doesn't seem to be working with this
arrangement (wondering if my test conditions are valid). Luckily I have
another Indy to check also - rig same MAP test - key on - 5.13V hmmm -
crank truck 4.5V hmmm - blip throttle..wild fluctuation - Bingo!
Start thinking about how this might relate to pinging. My truck with
bad MAP sensor is not able to accurately gauge load - duh - that has to
be it. Final sanity check - swap the known good MAP onto my truck -
test drive - NO PINGING WHATSOEVER! Not only that but huge difference
in power especially in the low end. I promise this isn't an April Fools
joke 8-). Ok now the big test - with a half tank of 87 octane in tank -
drive to Chevron and fill up with 93 octane. Back home - swap computers
to the performance one with more advanced timing - test drive - NO
PINGING!!! Massive power increase also most notably down in the low end
(where I thought my MPI had taken it away).
Sorry to be so long winded but I just wanted to relate my thinking
process in case it might help someone else. I am truly elated of my
results. To further prove this was my root cause of the pinging - I put
the expected bad MAP sensor on my other truck that has never pinged -
guess what? - pinging like a SOB! Confirmation.
The only down side was the fact that I left the bad MAP on my other
truck (wifes) - she probably won't even notice because she likes the
radio and I mostly just listen to the engine - nah she'll never notice
it. Major wrong answer - guess I should have married a blonde - dog
house big time 8-O
Enjoy!
Shane
-- '96 IndyRam-HisIndy-MPI/TB/Pulleys/Coil/Wires/CompTAs '96 IndyRam-HerIndy-numbered(#142)"Track Truck" '74 Triple-Black Dodge Challenger Rallye 360 home-brew EFI R&D vehicle '68 Black Corvette Convertible 427 (For Sale)
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:50:35 EDT