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98 3.9 v6 misfire under powered, sometimes
#739801 August 26th 2018 11:11 am
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Dw89xj Offline OP
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I have a 98 1500 with the 3.9 v6, it's been a great van and only has about 120,000 miles, but recently developed a misfire, sometimes, and sometimes seems to lack on power, not always while it's misfiring though. It is not throwing a code. It has had the plugs wires cap and rotor, air filter, module in distributor, and crank sensor all replaced within the past two months. Tried disconnec5ing battery, no change. I have a new cat to put on it since I can smell it sometimes, usually I notice the smell when it feels under powered, I have not changed it yet though. I have had it plugged into 3 different scanners none showing any trouble codes, any ideas why I get a misfire occasionally and other times it will run as good as a 6 can in a full-size van? Could it all be just a bad catylitic converter maybe o2 sensor causing it to lean out or be too rich due to a faulty cat? Sometimes you can smell unburnt gas at the tailpipe as well, but like I said no check engine light and no codes when it's plugged in. It doesn't get quite the economy it used to either, used to get about 380 miles per tank now getting about 320 give or take.

*** Edit *** also any plug wires that cross do so at 90° angles per the manual to avoid spark crossing wires.

Last edited by Dw89xj; August 26th 2018 11:13 am.

98 Dodge shorty hitop mark iv
95 Chevy van 20 regency hitop conversion van
Re: 98 3.9 v6 misfire under powered, sometimes
Dw89xj #739893 August 28th 2018 10:23 pm
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A plugged cat can sometimes cause those issues. I'd be initially more suspicious of something simpler. Have you checked and set base timing?

- Rich


1991 Dodge B250 Zephyr Conversion. "Bi-frost" 89,000-ish original miles and counting.
- 318TBI; has headwork and other bolt on upgrades. Runs strong and smooth!
- Powertrax locker
- 3" aluminum radiator.
- Rear air springs, rebuilt suspension, steering stabilizer.
Re: 98 3.9 v6 misfire under powered, sometimes
Dw89xj #739894 August 28th 2018 11:04 pm
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fuel filter on the frame my ford did the same think

Re: 98 3.9 v6 misfire under powered, sometimes
RichardB #739918 August 29th 2018 12:10 pm
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Originally Posted by RichardB
A plugged cat can sometimes cause those issues. I'd be initially more suspicious of something simpler. Have you checked and set base timing?

- Rich

I have not.


98 Dodge shorty hitop mark iv
95 Chevy van 20 regency hitop conversion van
Re: 98 3.9 v6 misfire under powered, sometimes
markdh #739919 August 29th 2018 12:13 pm
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Originally Posted by markdh
fuel filter on the frame my ford did the same think

I don't think this has your normal fuel filter, I think it's just a sock or built into the pickup and pump assembly, noone can find one under there unless it's very well hidden or very well camoflaged.


98 Dodge shorty hitop mark iv
95 Chevy van 20 regency hitop conversion van
Re: 98 3.9 v6 misfire under powered, sometimes
Dw89xj #739925 August 29th 2018 2:17 pm
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My tank is Midway under the van instead of in the back behind the axle. If that makes any difference for where the fuel filter might be hidden unless it's an in tank setup. My buddy says his Dodge pickup has the filter in tank with the pickup and pump assembly it's just the sock though. His truck is a 98 as well but a late model with the back doors not sure if which end of the year would matter either. I will say this, for replacement parts it's rare I get the right ones on the first shot. The van has roughly 120k. Mi.


98 Dodge shorty hitop mark iv
95 Chevy van 20 regency hitop conversion van
Re: 98 3.9 v6 misfire under powered, sometimes
Dw89xj #739926 August 29th 2018 2:26 pm
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Originally Posted by Dw89xj
Originally Posted by RichardB
A plugged cat can sometimes cause those issues. I'd be initially more suspicious of something simpler. Have you checked and set base timing?

- Rich

I have not.

It seemed to get slightly better after the distributor module, but still after it warms up or a long trip it seems to lose power the warmer the cat gets and you can smell it on long trips.


98 Dodge shorty hitop mark iv
95 Chevy van 20 regency hitop conversion van
Re: 98 3.9 v6 misfire under powered, sometimes
Dw89xj #739931 August 29th 2018 5:49 pm
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Change out the cat, its clogged .... if you can smell it ...its done,

More air thru more hp out


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'93 CHEVY G30 454 4X4 SPORTVAN EXT 146" WB
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Re: 98 3.9 v6 misfire under powered, sometimes
Dw89xj #739941 August 30th 2018 11:28 am
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I'm going to check the gap on the plugs too, I'm not 100% sure they're right. Don't know how much difference it might make but every little bit will help I'm sure.


98 Dodge shorty hitop mark iv
95 Chevy van 20 regency hitop conversion van
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