I agree with Andy. I had the same problem...replaced my throttle
position sensor and that fixed it.
Rascal
-----Original Message-----
From: owner-dakota-truck@bent.twistedbits.net
[mailto:owner-dakota-truck@bent.twistedbits.net] On Behalf Of andy levy
Sent: Sunday, November 17, 2002 11:02 PM
To: dakota-truck-moderator@bent.twistedbits.net
Subject: Re: DML: Re: Disappointing day at the dyno... Advice needed!
This small surge may be indicative of a bad Throttle Position Sensor.
Might want to check and possibly swap it before you start reprogramming
or taking other drastic measures.
William H. Hiatt III wrote:
> Well, I hooked up my OBD-II scanner on my laptop, and read the short
term
> fuel trim. It seems to be running rich (Average was about -12% for
bank one
> and -11 for bank 2). I would however constantly see -18% or so on both
> banks, with peaks of -25% on the banks. I can't read the long term
fuel trim
> (It's at 0) because the PCM hasn't learned yet.
>
> The reason I bring this up is after about 200 miles after the PCM
learns,
> the truck will start to surge about 200RPM here and there while
driving not
> under acceleration. Then it'll throw a a few 20X codes (Injector
control
> malfunction)
>
> Could this be because it's running way to rich? I do have those 21#
FMS
> injectors, coupled with the extra fuel in the LEACH PCM flash, minus
the
> extra timing in the flash?
>
> I'm going back to LEACH on Tuesday, and Tom is going to flash my box
and set
> the timing back up to 28.5 (Where he sets them all). Is the extra 3.5
> degrees enough to burn the rest of this fuel causing the truck to run
rich?
>
> Thanks
> william
>
> ""news.verizon.net"" <wE@.com> wrote in message
> news:ar1i83$dr9$1@bent.twistedbits.net...
>
>>Well I had a disappointing day at the dyno today. Only gained 1.4RWHP
and
>>5RWTQ, this is after the HO cams. This brings me to 225.4RWHP and
>
> 283.5RWTQ.
>
>>
>>
>>My guess is that 3.5 degrees of timing out of the PCM is making a big
>>difference! Also, you can see a steady decline after 4400 RPM of the
of
>
> the
>
>>TQ/HP curve.
>>
>>
>>
>>Changes between this run and last run:
>>
>>
>>
>>- HO cams
>>
>>- 21# FMS injectors
>>
>>- (-3.5) degrees timing on the PCM
>>
>>
>>
>>Other things that may make a difference between this run and last run:
>>
>>
>>
>>- I have a bolt in cat for the third cat now. There is a minor leak
around
>>where the cat bolts to the exhaust. I can tell this because water
leaks
>
> out
>
>>from where you bolt the cat in (I got ripped on the install job I had
this
>>crappy shop do)
>>
>>
>>
>>- I'm running a Robertshaw 330-180 thermostat. The problem is it's
such a
>>HIGH FLOW tstat, the truck doesn't warm up a lot of the times, and
trips a
>>check engine light. I'm thinking I should change it to a GT755-180
>>thermostat? Could this be affecting HP/TQ?
>>
>>
>>
>>Here are my questions:
>>
>>1) I think I need to get that timing put back in! 3.5 degrees must
make a
>>big difference
>>
>>
>>
>>2) HO intake?
>>
>>
>>
>>3) I'm going to remove third cat, and weld in some pipe between the Y
pipe
>>and muffler. My question is, should I go 3" between Y pipe and
muffler, or
>>go 2.5" to like halfway to the muffler. I DO NOT want to loose any
more
>>power, and I know our engines aren't that large, so we need to be
>>conservative on pipe size. Is this even worth doing?
>>
>>
>>
>>4) Anything else you can suggest based on my mods. Do I need to change
my
>>exhaust?
>>
>>
>>
>>Again, my mods are as follows:
>>
>>
>>
>>- Mike Leach PCM (With 25 degrees of timing instead of 28)
>>
>>- FMS 21# injectors
>>
>>- HO Cams
>>
>>- 4" Z-tube
>>
>>- Magnaflow 3" IN 2x2.25" OUT exhaust
>>
>>- F&B Throttle body
>>
>>- Robertshaw 330-180 Tstat (180 degrees)
>>
>>
>>
>>Sorry for the long post, this whole thing was kind of frustrating.
>>
>>
>
>
>
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