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bigb7000
Dodge Dakota
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10/27/2002
22:11:31
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 Subject: '97 3.9 loss of Power @ 70mph
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Message:
Ok, so I change the plugs and the old ones are toast gap ranges from 60-90 and two are really looking bad. New plugs gapped at 40 and truck seems to run fine up until I get on the Interstate. Seems like if I stay a steady 70mph after a little while I lose engine power so if you stomp the gas nothing happens back off and let it slow down to like 50mph I can gas it back to 70 or so. Also when this happens I noticed it was hard to break passed 80mph.. I have been well passed 120mph plenty of times before so I know something is wrong.. Is this an 02 sensor and which one I was told there are two top and bottom ones...
Also the check engine light came on and went away with the plug change. While the light was on I had AutoZone do an error code check and I believe he said top side 02 sensor but since the light does not stay on constant I was not sure if it was bad of wiring. So how many sensors are there where are they and also what is the correct plug gap for the 3.9?
Any help would be appreciated,
B
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Smitty1000
Dodge Dakota
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10/28/2002
00:08:40
|  RE: '97 3.9 loss of Power @ 70mph
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Message:
What's the milage?? It could be a number of things. The first thing I would do is pull the plugs back out and check the insulator for cracks. somtimes somthing as simple as a cracked plug can mess things all up. Make sure u use a spark plug socket to reinstall.Other than that,
a bad cat,wires,cap,rotor,cloged fuel filter, O2,ect. If its not the plugs I'd lean towards the Cat.
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Texas97
*GenIII*
10/28/2002
01:43:21
| RE: '97 3.9 loss of Power @ 70mph
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Message:
I seem to remember that the gap on my 97 was .35? I am not sure though, i cant remember, i changed those bad boys about 6 or 7 months ago, so i dont know. Dont know much about the O2 sensors, but I would be interested to find out...
Gig 'em Ags!
Kick the tires and light the fires!
97 Dakota CC 3.9L 5 speed
Mods: A lot of fun stuff
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BigB7000
Dodge Dakota
JOIN HERE
10/28/2002
09:02:55
| RE: '97 3.9 loss of Power @ 70mph
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Message:
I believe the milage is around 86K... I did use a spark plug socket the first time but I will pull them and check again... Funny thing is while I was changing them some other guys where there talking about car stuff and one guy had a story about a trip he took and his truck started having issues and he had some shop work on it with some fancy computer and could not figure out the problem. So as he went to spend the night he started talking to this older man who was like bring your truck over and I will help you look fix it. After working on it for a while they realized that one of the spark plugs had a crack in it... Doh...
Personally I have broken a plug in half before but never a crack... I will pull them tonight and look.
Thanks,
B
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rtdkota
R/T
10/28/2002
16:23:07
| RE: '97 3.9 loss of Power @ 70mph
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Message:
The fact the truck falls on it's face above 70 (should happen at the same rpm, regardless of speed)-- and you get a check eng. light that goes away, sounds like a misfire code. Don't skimp-- replace all of the plugs $.99 autolite 3923s or 3924s are fine (24s are stock heatrange)... Also make sure you have good wires-- test them-- you cannot always see cracking internally. ALSO-- you may have an issue with plugged fuel filter if the plugs are generally DRY, white in color. If they are wet (fuel), you most likely have an ignition problem (check the cap and rotor too). Fuel sync and other items could also be the culprit-- but not as likely.
Sam
RTDKOTA
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BigB7000
Dodge Dakota
JOIN HERE
10/28/2002
16:41:50
| RE: '97 3.9 loss of Power @ 70mph
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Message:
I did just change all the plugs...
The old ones were more off white than anything else except the last two I took out they had a dark line on one side...
I have not replaced the plug cables so I can do that... As far as RPM I would say just a little above 2K and it only has happend when at 70 for a few minutes steady... Normal driving the truck seems fine plenty of power and shifts fine. The check engine light seems to come and go so I was thinking the old plugs must have been letting alot of unused gas out and caused the sensor to become dirty... So I will get new plugs and wires but as for other things to check they might be too advanced for my skills...
Thanks,
B
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BigB7000
Dodge Dakota
JOIN HERE
10/28/2002
21:05:43
| RE: '97 3.9 loss of Power @ 70mph
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Message:
Ok, went to Napa and talked to them and the guys there think it is a fule pump issue... So I got the top side o2 sensor and I will attempt to change that out tonight... Any tips on that o2 sensor location and best way to get it out and back in?
Thanks,
B
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BigB7000
Dodge Dakota
JOIN HERE
10/31/2002
23:08:06
|  RE: '97 3.9 loss of Power @ 70mph
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Message:
***Update***
Ok, been 3 days and the truck has been running great... After changing the o2 sensor it has been fine... Just took it on a little trip 20 miles on the Interstate at 70mph and it was fine... Got it up to 90mph with no problem and backed off before getting a ticket... So I will keep you posted just in case it happens again...
Thanks for all the help,
B
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