I have a bizarre problem with my 98 Dak (318 4x4 manual). The problem is that under heavy
load, above 3000RPM it will occasionally lose power until the RPMs get to 3000 and then
stay there. It's just like a rev-limiter at 3000RPM. Except thta it only happens at full
or near full (throttle 80-100%) throttle, and can happen in any gear. It also seems to
happen more frequently when the truck is warm, but it is very difficult to reproduce
reliably.
I just got an OBD2 cable for my computer, and I had it reading when I got this problem.
The computer correctly determines RPM and throttle position (i.e. there is no RPM doubling
due to noise that I can see). (I didn't have all of the functions enabled, since that slows
down the OBD receiver too much).
My fuel-pressure gauge fluctuates +-5psi when it goes into this 'rev-limitter' mode, but
this is what happens when I blip the throttle several times (i.e. with the fuel consumption
changing rapidly), so I don't know if it is a pump, regulator, or computer thing.
I can hear the ignition through the radio (tuned to a non-existant AM station with the MSD
connected) and it sounds smooth (there is no noticable halting of the ignition when it hits
this mode (as I might expect with an ignition-cut-out rev-limiter).
Note that this has been going on for a long time (it doesn't happen all that often, so it
isn't THAT annoying, though it seems worse since I moved to Texas).
I have swapped plugs, distributor, tried with and without the MSD6a, new injectors, added a
supercharger, second fuel-pump/regulator (to boost the fuel pressure), 180-tstat, M1 m
anifold. It has had the same symptoms through all of this (before and after). It isn't
generating any codes when it happens. I don't want to bring it to the dealer, because it
doesn't seem like they'd be able to do anything besides guessing either (plus they'll
likely blame it on my mods, which I know aren't the problem)
The OBD2 sensor indicates that everything is fine (O2 sensos both appear to read fine, as
does air temp, manifold pressure, Throttle position, RPM, Coolant, etc)
I'm thinking that it is either the tank pump/regulator or more likely the computer, but I
have no idea why the computer would do something so foolish when all of the readings look
normal
Does anyone have a clue what eles I could try? I'd like to nail this down before having
my computer reprogrammed for the blower.
I created some graphs showing RPM, TPS and MAP while this was happening, which I could
post if nayone thinks they'd be useful)
Thanks,
Geoff
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This archive was generated by hypermail 2b29 : Fri Jun 20 2003 - 12:03:21 EDT