ZJ Problem?

[NW-ZJ-SCOTT]

so i picked this rig up 2 weeks ago, so far i have had 2 CEL's, one is p-0320 and the other is p-0420

The first one i was told was either a faulty o2, or a bad cat.
the other one was for a Crank position sensor.

Well with both of these codes i started having running problems.
at speed on a highway, the motor would surge, like a very minor hesitation..
Just while cruising, not trying to speed up, just during a constant rpm

well, yesterday it started a light Back-fire! i decided my issue had to be a clogged cat. took it to a shop, had a New o2 installed, along with a Magnaflow cat, and muffler with 3" pipe back to the bumper welded up, it sounds great, But i still have the hesitation, and the backfiring..


I have a CPS on order, it should be here in a week. does anyone think this sensor has anything to do with it? the CPS in my renix never acted up.. it just flat out quits on you!

Im confused:dunno:

 

[Jess]

sounds like it may be a fuel issue. Is it backfiring into the intake or out the exhaust?

If it is backfiring into the intake it is caused by a lean condition. Have you replaced the fuel filter? If that does not help you may want to check the fuel pressure. I know alot of people have issues with the ZJ's fuel pump.

 

[NW-ZJ-SCOTT]

It is out of the exhaust.

 

[jneary]

have you chacked the basics, plug wires or dist, cap for corrosion under the wires. also, the v8's were known to blow out the intake gasket under the manifold. one way to check for that problem is to see if there is vacuum on the breather tube where it attaches to the air cleaner.

 

[NW-ZJ-SCOTT]

i got a new CPS to throw in sometime this week. im hoping that solves it, the problem went from nothing on the test drive, to extremely annoying now, (in 2 weeks) its starting to backfire and hesitate on WOT..

After this sensor, im going to do a basic tune up (plugs/wires/fuel filter/air filter/cap&rotor)

then i'll start wondering Fuel pump/ Intake gasket. i dont want to start replacing things randomly. but at 165k im sure it could use it.

 

[jneary]

doesnt have a fuel filter on a '98.

 

[tharlanjr]

Does have a fuel filter, its just part of the fuel pump assembly...

 

[NW-ZJ-SCOTT]

well, i am pretty sure its not the fuel pump, as the issue is not just a "Cutting out" its a mis-fire thats causing a pretty apparent backfire threw the exhaust. Randomly i get a firecracker *pop*

I am trying to do the Crank sensor asap, but on the 5.9 it is VERY hiddin, im going to have to drop the crossmember and lower the TC/Tranny down a few inches, while disconnecting the exhaust from the Manifolds and lowering that down too.

I am sure its not the pump, pretty sure its not the ECM, so i will see what the CPS does, and do a tune up at the same time. from there its a guessing game. right now im just ruling things out.

Its getting to the point where im concerned enough to stop driving it.

 

[jneary]

you can access the cps from under the hood without lowering or removing anything. it just sits on the top of the bell housing on the upper right side. you cannot see it but you can feel the bolts. they should be 6mm hex head bolts.

 

[Israel]

When you replaced the cat and o2 sensor, did the p0320 code go away?

The other code may actually be from the CPS if there was a bad wire or connection. Or, maybe the sensor really is working only intermittently. Since the computer relies heavily on the CPS for timing, I can see the backfiring being related to a bad CPS.

 

[NW-ZJ-SCOTT]

OK, so, I replaced the CPS, took 15 hours. what a job!

Result: its starts quicker! fires up on the 2nd rotation..

thats about it for the good! its actually worse now. infact after a 30mile testdrive home, it is parked untill this is fixed, witch sucks as it is a daily driver for me and my wife.

It now backfires consistantly ever 10-30 seconds, normally 3-5 times in a row. extreme shuddering randomly.

My new suspicions: Timing! i am wondering if it is possible to adjust timing slightly with the distributor on the 5.9 magnum? Im also wondering if it is, if it has come lose? i believe its running lean as it took NO gas to get home (30mi normally takes 1/8+ tank) while under heavy acceleration it fell flat on its face on the freeway and backfired twice very loudly...


So, is the Dist. a probable possibility? the next thing i suspect is ECM. but i really have a hunch on the distributor...

input?

(btw, im exhausted, so my spelling sucks more then normal)

 

[MJmk]

Here's something to look at:

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

I'd check the cap & rotor, and the super long coil wire.