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Mystery problem 02 dakota 3.9

36K views 18 replies 10 participants last post by  ru4him 
#1 ·
I have a 2002 Dodge Dakota 3.9 4x4, and have had this problem for the last 3 years and 35 thousand miles. When it first starts it runs rough, not smooth at all. Then as you drive it coughs and pops (sounds like someone with a baseball hat under the hood). It will accelerate a little, how much depends on the day but usually around 25-40, while kicking and coughing. When it does this it will hit a point where it has very little power, feels like your pulling 20,000 lbs. If you keep your throttle steady, you wont accelerate anymore, floor it and in within 5 seconds, it gets full power back and kicks in strong. Like someone hit a NOS button. Sometimes it will come back sometimes its gone. The problem comes and goes randomly, its only a problem for the first 5 minutes after it starts then drives fine. I have had engine code 0300,0301,0303, Multiple cylinder misfire, cylinder 1, cylinder 3. P0351 Ignition Control. 0420, I replace driver side catalytic Converter and rear O2 sensor, and now have 0172. I also have replaced plugs, plug wires, and MAP sensor. I look on a scanner, even when I floor it the Throttle position reads 67% is that normal? The MAP reads close to 100 kPa. As for the engine codes I usually clear the code and it will go away, this hasnt been a consistent problem. Usually will last for a week or two, I put in a bottle lucas fuel injector cleaner and it goes away for a month or too. I cut back my driving by about 150 miles a week for a year and during that entire time I never had this problem. It seems to be more frequent when the weather is colder. Im not sure to what degree the timing should be advancing but im thinking I either have a crank position sensor, cam sensor, TPS, ignition coil or maybe a bad ecu? If anyone has any idea or suggestions please let me know. Thanks for the help.
 
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#2 ·
seems like you replaced the least likely components and left the most likely ones in place.

The throttle position does not sound normal, and when mine died I experienced similar (but less severe) issues with it having a 'dead' spot while accelerating. The TPS is a cheap part, so I would replace it next.

A bad upstream oxygen sensor can cause odd surging and bucking too without ever throwing a code. If you are getting p0172 and it is bucking and popping, I'm betting that the sensor is stuck rich and your bank 1 is running lean. 10 years is past the expected lifetime of an oxygen sensor, so it is probably wise to replace both UPSTREAM sensors as routine maintenance. You can get denso sensors fairly cheap on rockauto.

in my experience a bad crank sensor or a bad coil will cause the engine to completely cut out and not be isolated to a single bank. Not sure why fuel injector cleaner would clear it up.
 
#5 ·
Plenum gasket? I'd take a peek inside of the intake and see if you can see oil. Also a good indicator, if you check your oil regularly, is higher oil consumption. A bad plenum can cause all sorts of power issues and weird irregular problems depending on how bad it is. Every 3.9 or 5.2L engine I have had from Dodge has had the plenum bulging out to some degree if it was factory. Even the 40,000 mile 5.2L engine I bought to do a swap had a bulging plenum in it and it was only 2 years old when we pulled it, so it can happen at any time.
 
#6 ·
"Mystery" Problems Sound Very Similar ...

Thanks for the posts, bgrant. I've got very similar problems that have me stumped since last last Autumn. First the truck just started stumbling and quitting, then got worse over time (1998 Dak 3.9L, V6 basic with >100K mi). Only codes were some P300 cylinder misfire codes. Replaced the TBS. Got better for a few days, then came back.

Cleaned TB well, replaced some minor parts, ran Seafoam through the TB and tank, and problem got better for a few days. Then replaced TPS, then MAP sensor. Problem solved for a week. Then came back and now in addition to P300, P301, P303 and P305 codes I get a mysterious P351 code that indicates problems with coil. Finally replaced coil. Problem solved for a few days. Then came back, but subtly different symptoms. The "stumbling" and engine shut off for no apparent reason had gone, but started throwing same codes.

Had a mechanic spend many hours diagnosing and he ended up fussing with and tightening connectors to computer. He thought PCM was OK (but I still wonder). Ran great for two days. Now throwing P300 /302/ 303 /305 codes again (but not 351) and I have a complete loss of power about 40-50 mph with symptoms almost exactly as you describe.

It seems that there are more than one or two things in combination going bad, and/or there is some sort of cascading effect going on. BTW, my cat is now rumbling quite a bit and overheating the engine. Never had cat codes, but good guess I've ruined the cat in all this.

Now I'm reading here about intake manifold /plenum leak as well as O2 sensor, plus TPS issues. I think I'll do another complete tune up as well and replace the rotor (and maybe "pickup coil" in there as well) if I can afford all of this.

Anyway, keep posting about the "mystery problem" and maybe we'll get some sort of combination right to finally put this thing to rest... Can't help but believe our problems are caused by some things very similar.
 
#10 ·
So i bet you'd pissed to know that i just replaced both of my upstream o2's, with Denso's, and i got both of mine for 60 shipped to the front door? lol

I was going to post and tell you " hey man, order them from rock auto and use the forums discount code" but I was too late..
 
#13 ·
mystery problem as well

first a back story. i bought my 98 dakota back in december of 2012. a week later check engine light came on showing both o2 sensors, but the vehicle seemed to run good. a week and a half ago i drove it approx. 30 min parked it. an hour later when i started it back up it was idleing somewhat rough. if i would give it gas it would clear up. i decied to drive home. every stop light i would keep my foot slightly on the gas to keep it running smooth. 3/4 of the way home it bogged down and was jerking if i would give it gas. it was jerking very hard. i had to barely give it gas (5mph) and pulled into the nearest parking lot. i shut it down and looked over the engine for around 5-10 min. nothing looked unusual. i started it back up and made it close to 1/8th mile down the road before it came back. with nowhere to pull over i decided to try to make it home at the 5mph pace. 2 miles later it came back to life. dropping power after every shift, then instantly coming back. i rechecked the check codes and it said cyl 2 mis fire. along with bank 1 sensor1. I replaced the cyl 2 plug and wire. I then took the same 30 min trip and no prob until i came back home. i the replaced the dis. cap and rotor. took trip waited then came home, no problem. drove a 45 min trip to work, no problem. 1 mile from leaving work it was the worse it has ever been. i pulled over and even giving it gas wouldn't clear it up. i had it towed to my mechanic. they replaced the bank 1 o2 and said it was all good. i picked it up and it seemed fine. the next day 1/2 mile out of the drive way i could tell something was up. i pulled it back into my driveway and let it run. after about 15-20 min it went to the VERY ROUGH idle. check code now says bank one and two sensors voltage high. i drove it back to the shop. it drove ok, but not great. they said when they started it up in the morning it would barely run. side note: i ran some test on the cat before i took it back and it had metal and ceramic coming out the tail pipe. it had a bad rattle and also after a heat test the front of the cat was double the temp of the back. the shop said the cat is bad but not the problem. they claimed to test every sensor and couldnt figure it out. they said they unplugged both o2 sensors and it is running fine. i told them to keep it and to drive it often. any ideas on what it could be? me and my shadetree mechanic friends and the so called professionals are stumped.
Also not sure if it matters but everytime it does this it is either raining or very wet. the dry days it was fine.
 
#14 ·
first a back story. i bought my 98 dakota back in december of 2012. a week later check engine light came on showing both o2 sensors, but the vehicle seemed to run good. a week and a half ago i drove it approx. 30 min parked it. an hour later when i started it back up it was idleing somewhat rough. if i would give it gas it would clear up. i decied to drive home. every stop light i would keep my foot slightly on the gas to keep it running smooth. 3/4 of the way home it bogged down and was jerking if i would give it gas. it was jerking very hard. i had to barely give it gas (5mph) and pulled into the nearest parking lot. i shut it down and looked over the engine for around 5-10 min. nothing looked unusual. i started it back up and made it close to 1/8th mile down the road before it came back. with nowhere to pull over i decided to try to make it home at the 5mph pace. 2 miles later it came back to life. dropping power after every shift, then instantly coming back. i rechecked the check codes and it said cyl 2 mis fire. along with bank 1 sensor1. I replaced the cyl 2 plug and wire. I then took the same 30 min trip and no prob until i came back home. i the replaced the dis. cap and rotor. took trip waited then came home, no problem. drove a 45 min trip to work, no problem. 1 mile from leaving work it was the worse it has ever been. i pulled over and even giving it gas wouldn't clear it up. i had it towed to my mechanic. they replaced the bank 1 o2 and said it was all good. i picked it up and it seemed fine. the next day 1/2 mile out of the drive way i could tell something was up. i pulled it back into my driveway and let it run. after about 15-20 min it went to the VERY ROUGH idle. check code now says bank one and two sensors voltage high. i drove it back to the shop. it drove ok, but not great. they said when they started it up in the morning it would barely run. side note: i ran some test on the cat before i took it back and it had metal and ceramic coming out the tail pipe. it had a bad rattle and also after a heat test the front of the cat was double the temp of the back. the shop said the cat is bad but not the problem. they claimed to test every sensor and couldnt figure it out. they said they unplugged both o2 sensors and it is running fine. i told them to keep it and to drive it often. any ideas on what it could be? me and my shadetree mechanic friends and the so called professionals are stumped.
Also not sure if it matters but everytime it does this it is either raining or very wet. the dry days it was fine.
That points to bad plug wires and / or bad distributor cap and / or bad coil. I'd suggest replacing the spark plug wires (and routing them correctly) and distributor cap before doing any more troubleshooting.

Have you routed the spark plug wires correctly per the TSB?

http://dodgeram.info/tsb/1998/18-48-98/18-48-98-v8.htm
 
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