Hi Jon,
Try it again after it warms up. I think you'll find it is ok. One place
where I used to work has several stop and go's before reaching the street.
I would get to about the third or forth one when leaving for the day, and
the same thing would happen to me. "POP", this was a moderate backfire up
through the intake and TB, but very noticeable. This is the only place it
ever repetitively happened, so I believe there is a "critical region" during
warm-up where the conditions are just right for this to occur. Outside this
parking lot, I think it might have happened once.
Rich - Ashburn, VA
(your twin '96 CC 318)
-----Original Message-----
From: Jon Steiger [mailto:jon@dakota-truck.net]
Sent: Friday, April 07, 2000 4:05 AM
To: dakota-truck@buffnet.net
Subject: DML: Throttle body backfires
Does anyone know what causes a backfire through the TB? I've got the
4bbl bolted onto my Dak and the sensors sort've hooked up. (Nothing
permanent, just to get the engine fired up.) Anyway, after checking the
readouts on the sensors I fired it up. It ran exremely rich for maybe
20-30 seconds or so, then started to level out. The temp came up a little
bit and it went into closed loop; the computer seemed to be able to switch
rich/lean to maintain stoich without any difficulty. I don't have the
throttle cable hooked up yet, so I just moved the throttle linkage by
hand. I never let the rpms get really high, but I noticed if I opened it
slowly, it seemed ok, but if I snapped the throttle open relatively quickly
like what might happen if you blipped the throttle, I would sometimes hear
a pop inside the intake, which sounded like a backfire to me. Is it
possible that the engine needed to warm up some more? (I think the coolant
temp got up to about 150-160 or so.) Or could it be something else? I
didn't push it; I had visions of this expensive work of art blowing off my
engine and taking my hand with it. ;-) Speaking of which, how much power
can a naturally aspirated intake backfire create? Enough to damage the TB?
Anyway, I think I'll let the truck warm all the way up and try again,
but I thought I'd throw this out there to see if anyone had any ideas, and
to find out exactly what causes a backfire through the TB. (Could it be
too much air?)
For the record, the engine is a '96 318, MP computer, 4bbl TB, MPI
intake, JBA headers with 1 5/8 primaries dumping into a 2.5"->3" Y pipe,
then 3" all the way back through a Gibson muffler (no cat).
Thanks!
-Jon-
.--- jon@dakota-truck.net -- or -- stei0302@cs.fredonia.edu ------------.
| Jon Steiger * AOPA, DoD, EAA, MP Race Team, NMA, SPA, USUA * RP-SEL |
| '92 Ram 150 4x4 V8, '96 Dakota V8, '96 Intruder 1400, '96 FireFly 447 |
`---------------------------- http://www.cs.fredonia.edu/~stei0302/ ---'
This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 11:50:37 EDT