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1Farmer
Dodge Dakota
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7/28/2010
18:28:13
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 Subject: 98 Misses during warm-up
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My 98 3.9 will start to miss after driving a couple miles from a cold start. Seems fuel related. Will almost die if running 1500-2000 rpm's, but only does it for a couple miles. Starts good, runs good up to that point, and runs fine after it is fully warmed up. No codes. I suspected O2 senser, but parts store says no. Help!
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jandjauto
GenII
8/07/2010
01:36:55
|  RE: 98 Misses during warm-up
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Message:
could be a number of thingsbad
cap and rotor
wire
plug
or posible injector prob check all the injector
connections
what I usualy do is spry them with carb or brake clean
than either let them dry or blow them dry with air
Larry
J&J Auto
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1Farmer
Dodge Dakota
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8/18/2010
18:06:49
| RE: 98 Misses during warm-up
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Thanks for the info. I tried the cap and rotor. I was going to do the wires, but it seems strange that it only does it when you first start driving. It runs fine if the first 1/2 mile or so, and then will act up but only for the next mile or so. Then it runs fine again. I was thinking it must be temperature related. I was thinking about changing the Manifold Air Temp sensor, or coolant sensor but the parts guys talked me out of it without getting a code. I would think if it were injectors, I would have more symptums. I could try the wires if you still think that could be it.
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yea
Dodge Dakota
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8/18/2010
20:18:15
| RE: 98 Misses during warm-up
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Possible Dist. bushing or gear.
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daddio
Dodge Dakota
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8/18/2010
21:36:52
| RE: 98 Misses during warm-up
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Have you checked for codes? It sounds like a temp sensor related problem. And it seems like when the PCM is transitioning from Open Loop to Closed Loop.
Check for codes and if none found a DRB Scantool would be your friend and you could see exactly what's going on when it starts to act up.
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1farmer
Dodge Dakota
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8/19/2010
12:20:04
| RE: 98 Misses during warm-up
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I think you are on to something. I don't get any codes, but the temp sensor thing makes sense. I don't have access to a DRB scan and am trying to avoid a dealer service. Do you think it would be worth the gamble to try replacing the air and/or water temp sensors? If so, which one would you try first, or should I just do them both at the same time?
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1Farmer
Dodge Dakota
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8/19/2010
15:09:38
| Open Loop vs Closed Loop
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I had another thought. Thanks to Daddio's feedback I did some research on open loop verses closed loop operation. It seems possible that if the PCM is switching to closed loop prior to the O2 sensors being operational, that I would experience a fuel mix problem. Could this be as simple as an O2 sensor heater failure? I'm thinking that when the 02 sensors heat up from exhaust they begin to provide accurate data and the mix is corrected. My original first guess was O2 sensors but after describing the problem, my parts guy assured me that could not be the issue.
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daddio
Dodge Dakota
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8/19/2010
20:35:47
| RE: 98 Misses during warm-up
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Temp sensors are cheaper than O2 sensors. And if it is a temp sensor it would be the engine temp sensor. That is the one that the PCM uses. the other is for the gauge only.
Usually a faulty O2 heater will trip a code. If you could find the info you could check the heater circuit on the O2's. I'm sure there is a specific range of resistance that would indicate their condition, good or bad.
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1Farmer
Dodge Dakota
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8/19/2010
23:37:10
| RE: 98 Misses during warm-up
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Thanks. Sounds like a good place to start. One thing that puzzles me is that it will do this even if the guage shows water temp is hot. For example, I can start cold in the morning and it will do the typical stunt. If I go to a store and shop for a while, It will do it again when I leave even though it hasn't sat long enough for the coolant to cool down. I've watched the coolant guage to see if the problem occurs when the temp guage hits a specific point, but that doesn't seem to be the case. But as you said, for the money I think I'll try that first. Thanks again.
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daddio
Dodge Dakota
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8/20/2010
11:48:13
| RE: 98 Misses during warm-up
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Remember, change the coolant temp sensro for the PCM NOTR the gage. They use 2 different ones and even if the sensor for the gage does not work properly it will not affect the data the PCM uses for input.
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TomN
Dodge Dakota
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8/21/2010
18:04:48
| RE: 98 Misses during warm-up
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Where is the temp. sensor for the gauge? I thought there was only one temp.sensor on a 1998 which is located right next to the tstat.
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