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reapist
Gen I
 
11/04/2007
09:15:37
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 Subject: Stumbling at WOT
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Message:
Last spring I decided to change the oxy sensor in my 94 Dakota w/5.2 not because it was running poorly, but because it had 150k miles and had never been changed. I went to the parts store and they sold me one that I discovered was kind of generic. I had a different hole pattern than my original and while it performed well with normal driving it fell all over itself at WOT. I went to the dealer and got an original replacement and it worked fine.
Since then I've replaced the factory breather with one that can breath well and it's still doing fine...untill yesterday. I put new headers on and had a new exhaust system run with a free flowing cat, muffler and 3" pipes. At partial throttle it does great. I can feel it has more power. But at WOT it surges then stumbles, then surges and stumbles again.
The guy didn't replace the Y pipe and that's where the oxy sensor is at so I kind of think that's not it. I don't think it's the leaky plenum gasket, but I do have a new M1 intake in the garage, just waiting for the gaskets to come in. I think maybe it's the fuel supply.
My guess is that the 19# injectors just can't keep up now at WOT. What do you guys think?
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Marv
Dodge Dakota
JOIN HERE
11/04/2007
09:30:53
|  RE: Stumbling at WOT
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At WOT, the engine computer disregards O2 sensor inputs and uses a pre-programmed fuel delivery scheme. In fact, at WOT, all emissions sensors are taken out of the loop, and pre-programmed parameters are used. That's why your engine has a WOT switch.
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daddio
Dodge Dakota
JOIN HERE
11/04/2007
18:45:26
| RE: Stumbling at WOT
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you haven't done near enoug mods to require bigger than 19# injectors. have you checked for any codes? when was your last tune up?
Marv, what is a WOT switch? never seen such a thing on any Dak i've seen.
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Marv
Dodge Dakota
JOIN HERE
11/04/2007
22:00:05
| RE: Stumbling at WOT
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Message:
Perhaps "switch" was the wrong word.
It's one end of the Throttle Position Sensor variable resistor.
Shamelessly cut and pasted from my pdf version FSM:
The TPS is a 3wire variable resistor that provides the Powertrain Control Module (PCM) with an input signal (voltage) that represents the throttle blade position of the throttle body. The sensor is connected to the throttle blade shaft. As the position of the throttle blade changes, the resistance (output voltage) of the TPS changes.
The PCM supplies approximately 5 volts to the TPS. The TPS output voltage (input signal to the PCM) represents the throttle blade position. The PCM receives an input signal voltage from the TPS. This will vary in an approximate range of from .26 volts at minimum throttle opening (idle), to 4.49 volts at wide open throttle. Along with inputs from other sensors, the PCM uses the TPS input to determine current engine operating conditions. In response to engine operating conditions, the PCM will adjust fuel injector pulse width and ignition timing.
The PCM needs to identify the actions and position of the throttle blade at all times. This information is needed to assist in performing the following calculations:
Ignition timing advance
Fuel injection pulse-width
Idle (learned value or minimum TPS)
Off-idle (0.06 volt)
Wide Open Throttle (WOT) open loop (2.608 volts above learned idle voltage)
Deceleration fuel lean out
Fuel cutoff during cranking at WOT (2.608 volts above learned idle voltage)
A/C WOT cutoff (certain automatic transmissions only)
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Reapist
Gen I
11/08/2007
10:23:16
| RE: Stumbling at WOT
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I'm watching the tach and beginning to think it's the rev limiter. Does the performance PCM have this rev limiter? It's down the road but it is in the plans.
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modain
GenIII
11/08/2007
11:39:17
| RE: Stumbling at WOT
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Message:
I was thinking rev limiter. At what RPM does this happen? I'm pretty sure the stock RPM limit is somewhere above 5200, maybe around 5500.
The Mopar performance PCMs do raise the limit. Are there Mopar PCMs produced/available for your truck's year? If not, you'll need to look into a custom flash if you want to run those high RPMs.
What's your left foot doing?
==============
2002 Graphite QC SLT Plus, 4.7L, NV3500, Superchips 3715, 3.92 LSD, R/T rear swaybar, no chrome, loads o'fun...
2001 Patriot Blue Durango SLT, 4.7L, 45RFE, Superchips 3715, 3.55 Open (for now)
1999 Forest Green Dakota RC Sport, 2.5L, NV1500, 3.55 Open
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Reapist
Gen I
11/08/2007
17:14:01
| RE: Stumbling at WOT
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It's stumbling aroun 5k and the tach is redlined at about 4800. I've been told the 94 computer is not flashable but yes, there is a performance PCM which I will probably be picking up in about 3 weeks.
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Uh Oh
Dodge Dakota
JOIN HERE
11/08/2007
23:46:40
| RE: Stumbling at WOT
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I think there are two different WOT definitions going on here.
In engine control, WOT is throttle fully open, regardless of engine rpm or vehicle speed.
I get the impressiion that to Reapist, WOT means engine running at the rev limit.
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Reapist
Gen I
11/09/2007
09:48:47
| RE: Stumbling at WOT
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Message:
Not really. I just haven't run the RPM that high at partial throttle. But I probably should try that. I would guess that if I'm hitting the rev limit the shift points should be lowered. Not sure if a shift improvement kit would take care of that or if it just is what it is though.
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