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2007 Dakota Quad cab 4x4, multi issues need some sugestions please

2698 Views 14 Replies 3 Participants Last post by  FaceDeAce
I have owned this low millage ( about 80K) Dodge Dakota 4.7 for about a year and a-half, most of the time it seems a good and reliable truck but some strange recurring and intermittent issues. First some history, initially showed up as drive-ability issue that happened twice about 4 or 5 weeks apart about 10 months ago. Both times with about a 1/2 tank of gas. After idling for several minuets it would stumble, have no poor and seem to be choking out and not able to make head way more than to get out traffic. Once after limping to gas station and filling up all was good again. Anther time simply waiting 15-20 mins all was OK. No CEL or code until later. First Though fuel pump issue since the code that eventually showed up was something about lean mixture ( don't recall the code exactly ) had the Truck checked out full expecting needing to put in a new fuel pump but they said it was fine and could not find any other issue that might need attention. All was fine for several more months, but when getting an air inspection was told the gas tank cap was bad so replaced. ( again no CEL and no issues) including letting the tank get to or below 1/4 several times...
Fast forward several months ( and after a move to another state) with no issues...
Have now had a couple of times the CEL was on, first though fuel cap and after the next fill up CEL out and all was OK again for a few weeks. Now CEL on again - no codes? tried to check the codes twice on different days - nothing shows up. No recurrence of the drive-ability issue like before but have noticed that sometimes it seems to idle a little rough on start-up and of late the mileage is down from normal ( which has never been that good but better that the current 9 or 10 MPG) Also twice, once a couple of months back (no CEL) and again recently ( with CEL on ) it would surge on idle after start up and be idling rather high (over 1200RPM) have been keeping the top half of the tank full most of the time but this has now happened again with about ( just over) 1/2 tank.
Like this truck but begining to like it less.
Any help would be appreciated, in the mean time I am going to try and look for the obvious stuff like a vac hose off ERG valve etc, and some other things I was able to find here in the forms.
Thanks in advance!
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First two things that came to mind, you have mentioned you will look into checking or replacing: look for vacuum leaks, check PCV and vent tubes, check vent tube orifices for blockage, replace the EGR. The third item you did not mention, replace the spark plugs. Use copper only. Best in mine are the NGK 2262.
Usually, if the check engine light is on there is a code. Really odd if there isn't. With no codes, it can be difficult to get down to what is the root problem. There are many things that will turn on the engine light. It gets expensive fast just replacing each one of them until the culprit is found.

Thinking and going the easiest route first. Spark plugs can definitely be a cause. It could be having random misfires from bad plugs, different cylinders at different times, etc. Perhaps because it isn't consistent the PCM does trigger anything specific, just showing that something isn't right. If you haven't changed the plugs within the past 30k, they are overdue. Low cost, easy to do, only an hour or so of your time.

The canister, is part of the evap system. Based on your feeling and fuel cap notes above. Perhaps it is related. Best to get the truck up on ramps so it is easier to scoot around underneath for checking the related lines.

A sticky or just generally dirty throttle body can also cause such things and periodic cleaning of it does some wonders. That is quite easy to do too.
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I strongly suggest you start with the spark plugs and do only that plus add a bottle of fuel system / injector / engine cleaner to the tank to clear up the combustion chamber of residue from old half firing plugs.

O2 sensors rarely fail. Emissions issues and codes are easily affected by plugs and throttle body. See what happens afterward with some runtime of a tank or 2 on the new plugs and TB cleaning before going to next items. Do think about those other things, but start simple.

Also, what gas are you putting in the truck? The high ethanol blends of 85 and some 87 can cause weird issues. As a trial you should try a tank of 89 or even 91 and see what happens.
Yeah, getting to the EGR is a real pain in the knuckles. Not all that bad, just patience and contortions to get it done. Hopefully you do not have to go there. If you do, this other thread may be helpful to get your head around what you might find.

Crossing fingers for you that a new set of NGK #2262 spark plugs (V-Power) will completely resolve this for you.

Looking forward to letting us know if the scanner shows any more codes that can be helpful!
Although the P0420 code indicates O2 and/or catalyst, remember that anything upstream of those sensors that is not operating properly will cause the exhaust parameters to go out of range thus indicating a problem downstream. Because your mileage and power are suffering somewhat, looking things like spark plugs, vacuum leaks, dirty fuel injector, EGR are the first places to look and verify. If those check out 100%, then look more closely at O2 diagnostics to determine which one(s) to replace. If the O2 sensor data is active, meaning the "live" raw numbers are changing fairly rapidly 2 to 3 times per second then they should be fine. A pause in O2 reading is dependent on the running condition. For example if sitting at idle, such as just started and during warm up, the PCM would go into a fail safe mode which means it force sets the O2 reading to some default number. Once the truck is moving, above idle, rolling down the road, the data point becomes active and is used in the fuel management loop. If you see a data point paused, blip the throttle, that would cause PCM to drop out of that default mode, if only momentarily.

... yes, spark plugs first. Cheapest, easiest, largest impact and benefit from least effort. Pun risk: biggest bang fo the buck.

Hope that helps!

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Pleased to see the advice was helpful and things are sorted out. Enjoy!
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