RE: RE: misfire/backfire 02 Dakota 3.9

From: Bernd D. Ratsch (
Date: Tue Dec 08 2009 - 06:25:00 EST

Swap out the #1 and #3 plugs - see if the popping, swap the plug wires, again...check for the popping. Narrow it down as much as you can before spending any large amounts of money. Compression sounds ok. I'd be curious on the vacuum though when it's popping.

- Bernd

-----Original Message-----
From: []
Sent: Monday, December 07, 2009 10:01 PM
Subject: Re: DML: RE: misfire/backfire 02 Dakota 3.9

Ok, tested Compression, cranking I got around 160/165

Running I got around 90/100.

I wasn't able to get vac as I dunno where my vac guage disapeared to!

I disconnected #1 injector, measured around 13 ohms (engine was hot) and compared it to the other 2 on bank 1 and all were about the same.

With it unhooked I got no popping, so it's cyl #1 for sure...

Plug (new 1 week old) was very white confirming lean cond.


was told it could possibly be a valve guide came loose?

have to have to spend $$$ to have that torn down :( I just don't have time to be pulling heads rite now.


--- wrote:

From: "Bernd D. Ratsch" <>
To: <>
Subject: DML: RE: misfire/backfire 02 Dakota 3.9
Date: Mon, 7 Dec 2009 05:18:51 -0600

P0172: Fuel Trim System Rich Bank 1 (Driver-Side)
P0301: Cylinder #1 Misfire (not necessarily an injector)

Definitely sounds like something is wrong with #1....i'd be checking compression and actual engine vacuum before replacing anything else. Compression, running compression, and vacuum will give you the direction to go.

- Bernd

-----Original Message-----
From: []
Sent: Sunday, December 06, 2009 11:48 PM
Subject: DML: misfire/backfire 02 Dakota 3.9

Well, after replacing cap rotor, plugs, wires. it still pops thru the intake under load at low rpms, (sometimes) and for the 1st time the eng light came on!

Got po172

misfire only cyl 1, new plug & changed out wire again still no go.

I did look down the TB for oil, pretty clean, very very little oil or anything.

I'm looking at injector next????

when it's popping in OD if I step on it hard it goes like a bat outta hell...

$72 for an injector, figured I'd post my findings befor I spend $$$ if it's not gonna help!

thanks much!


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