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Pat
Dodge Dakota
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4/29/2004
17:11:44
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 Subject: RE: Stutter...Zoom!...Stutter... What gives?
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I spoke too soon. Apparently, some IDIOT that was looking at the MAP sensor, left the connector unplugged (too bad I'm the only person who's worked on this truck.). But I replaced it anyway, reset the computer again and read the codes. 55.
So I am back to square one.
Now, although I did change the Distrib. Cap and Rotor, I didn't look for points (frankly, I didn't see any) nor did I look for that mysterious Hall Sensor thing that lurks beneath the rotor (what does that thing do, anyway?). So, I'm gonna replace the plugs and wires, since it's time for it anyway, and then I'll stand there wondering what to do.
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?
Dodge Dakota
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4/30/2004
08:08:51
| RE: Stutter...Zoom!...Stutter... What gives?
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Sensor ( hall or other ? ) in dist. is used
for fuel injector syncing..
Spark timing is from CPS - mounts in
transmission bell housing - just below and
to pass. side of dist..
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Bob Lincoln
Dodge Dakota
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4/30/2004
08:47:04
| RE: Stutter...Zoom!...Stutter... What gives?
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Message:
So now that you found the problem with the MAP sensor, how does it run? You don't mention whether it behaves the same.
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Pat
Dodge Dakota
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4/30/2004
08:56:40
| RE: Stutter...Zoom!...Stutter... What gives?
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No change. Still sputters. The problem wasn't the MAP sensor, apparently. Guess it's some other gremlin in the open-loop mode, but I don't know what to check next, since I'm not gettin' any codes.
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??
Dodge Dakota
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4/30/2004
09:00:32
| RE: Stutter...Zoom!...Stutter... What gives?
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When the engine is started, the hot exhaust gases pass by the oxygen sensor. When the sensor temperature reaches 600° F, it becomes conductive for oxygen ions. If the amount of oxygen electrons on the exhaust side are equal to the amount on the ambient air side, then the electrons equalize and no voltage is produced. As the oxygen content of the exhaust decreases, an imbalance occurs and the oxygen sensor begins to produce a voltage.
Normal operating voltages for the oxygen sensor range from a low of 100 millivolts to a high of 900 millivolts. The voltage produced can occasionally be higher or lower than these figures. About halfway between these voltages is 450 mv - known as the crossover point. Any voltage less than 450 mv is interpreted by the computer as excessive oxygen caused a lean exhaust condition; any voltage greater than 450 mv is interpreted by the computer as insufficient oxygen caused by a rich exhaust condition. Anything that affects the content of oxygen in the exhaust will affect the oxygen sensor signal.
When the oxygen sensor voltage is indicating a lean condition, the computer will respond by enriching the mixture. When the oxygen sensor voltage is high, the computer will respond by leaning out the mixture. In this manner, the computer adjusts for minor errors and variations from the rest of the input sensors and controls the air fuel ratio at 14.7: 1.
The oxygen sensor itself is a very dependable unit. Occasionally the oxygen sensor will fail with an internal open circuit. The most common problem that occurs with oxygen sensors is contamination. There are three common sources of contamination for the oxygen sensor:
RTV silicone - a commonly used sealer and adhesive. The fumes from this adhesive can coat the oxygen sensor, slowing its ability to respond to changes in the oxygen content of the exhaust. When the oxygen sensor becomes con- taminated with silicone, it delivers a lean signal to the EEC computer.
Leaded fuel - not readily available now. When the oxygen sensor becomes contaminated by leaded fuel, the output voltage will be stuck above the crossover point. This is a rich exhaust indication. Although this rarely occurs by accident, be sure to check the contents of any fuel additives being used to ensure that it does not contain tetra-ethyl lead.
Soot contamination - The two primary sources are oil and fuel. Oil soot is a result of a mechanical engine condition such as worn rings or valve guides. Fuel soot is either the result of a rich-running engine or a misfire. Either form of soot impedes the operation of the oxygen sensor. The output voltage remains constant at around 0.5 volts
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Pat
Dodge Dakota
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4/30/2004
14:55:28
| RE: Stutter...Zoom!...Stutter... What gives?
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Message:
I agree that the O2 sensor is suspect, mainly of soot contamination, but that is only a factor AFTER the computer switches the engine to "closed-loop mode". My concern is that the engine is running extremely rough in "open-loop mode" - the first couple of minutes after being started, when any readings from the O2 sensor are ignored by the computer while the O2 sensor has a chance to warm up. There are other parts and sensors that are in play during these 2 minutes, and it is these parts/sensors that I must test and fix first.
If the engine only ran rough AFTER this initial 2 minutes, I would know it was a sensor or part used in closed-loop mode, such as the O2 sensor, and I could test it and fix it. But it is rough from the very start. If the engine is running far too rich - due to some other sensor/part malfunction - and I replace the O2 sensor without FIRST fixing THAT, then there is every chance I will foul the new O2 sensor with the same soot that fouled the last one. Don't know about you, but I don't have a bunch of spare $60 O2 sensors laying around.
So what I have to troubleshoot is, just what sensor or part in OPEN-LOOP MODE is keeping me from having that stoichiometric blend (the perfect blend of fuel to air, in ideal proportions) or messing up my timing, so that my little Dak is stumbling all over the place.
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?
Dodge Dakota
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4/30/2004
15:21:34
| RE: Stutter...Zoom!...Stutter... What gives?
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Have you inspected/replaced Plugs/wiring yet??
rotor ?
Does it run even for first minute , better
after resetting ?
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TAZ Miller
Dodge Dakota
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5/01/2004
20:26:58
|  RE: Stutter...Zoom!...Stutter... What gives?
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I have an 87 Dakota 3.9 with a carb. I have the same problems as you , she`ll hiccup and fart not wanna run right. I have replaced everything but the heads,block and intake,,everything is new or rebuilt, I am at loss as to what to do next, so far I have spent almost 1150 bucks on this truck and she still will go 10 or 12 miles and start hesitating and falling out from under me, I give her more throttle and she goes to pieces and wants to die. I have to stop her shut her off and let her sit for a few minutes then fire her back up go for another 3 or 4 miles then crap out again,,,any help would be appreciated ya`ll TAZ
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DiMoose
Dodge Dakota
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5/04/2004
18:20:43
| RE: Stutter...Zoom!...Stutter... What gives?
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Message:
Same problem with my 98 Dakota,also 3.9 mag v6. At first I thought it was the IAC also, cleaned it...no dice..... or a clogged Cat Conv., which could foul the O2 Sensor(upstream) I believe. My truck idles slightly rough at startup and stalls for the first 20 minutes or 10 miles at stop under load. The truck is paid for and has 85k on it. It would probably be better if I just bought another truck ; ). That decision will be made If I get it back from Pat Goss, and the problem isn't fixed. If it's fixed I'll let you guys know what it was.
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