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Rough idle, running rich

13K views 16 replies 3 participants last post by  zach98ram 
#1 ·
Hey everyone, im new to the forum and i'm having troubles with my truck. Its a 1998 dodge ram ss/t 5.9 and its running rough at idle and misfiring on cylinder 2 and 4. I changed the plugs (copper champions), wires (msd super conducter 8.5mm), cap and rotor (standard blue streak with brass contacts), and pre cat o2 sensor (ntk from dodge dealer). I checked for vacuum leaks and can't find any. Fuel pressure is around 49psi, all the injectors show 12.2 ohms. Fuse for the o2 sensor is good. I tried unplugging the front o2 sensor and it didn't help. Cleaned iac and throttle body. I reset the pcm after each time i changed or checked something. I'm running out of ideas and need suggestions. Thanks everyone
 
#2 ·
Check/separate 2 and 4 plug wires; double check plug wires for correct firing order (18436572).
... Being they're neighboring cyls could be head gasket; would do compression test. ... Welcome to DT
 
#3 ·
I got my truck back together. I ended up replacing the heater hose pipe. I changed the o rings on the injectors too. I took it for a drive an there is no more misfire codes, but there is a p0132 and p0138 codes. Its running really rich too. It wants to stall when i slow down for an intersection. I did a compression test to

Cyl 1 - 160 dry 170 wet
Cyl 2 - 160 dry 165 wet
Cyl 3 - 165 dry 173 wet
Cyl 4 - 145 dry 155 wet
Cyl 5 - 158 dry 160 wet
Cyl 6 - 150 dry 158 wet
Cyl 7 - 153 dry 158 wet
Cyl 8 - 160 dry 165 wet

I'm a little concerned with cyl 4. Its a little over 10% difference. I don't think this would cause the engine to run rich, but i'm not happy to see this on a longblock with 25000 kilometres on it. Does anyone know how to test the o2 sensor and the wires going to it. I already tried unplugging it and it didnt make a difference. Thanks
 
#4 ·
I got my truck back together. I ended up replacing the heater hose pipe. I changed the o rings on the injectors too. I took it for a drive an there is no more misfire codes, but there is a p0132 and p0138 codes. Its running really rich too. It wants to stall when i slow down for an intersection. I did a compression test to

Cyl 1 - 160 dry 170 wet
Cyl 2 - 160 dry 165 wet
Cyl 3 - 165 dry 173 wet
Cyl 4 - 145 dry 155 wet
Cyl 5 - 158 dry 160 wet
Cyl 6 - 150 dry 158 wet
Cyl 7 - 153 dry 158 wet
Cyl 8 - 160 dry 165 wet

I'm a little concerned with cyl 4. Its a little over 10% difference. I don't think this would cause the engine to run rich, but i'm not happy to see this on a longblock with 25000 kilometres on it. Does anyone know how to test the o2 sensor and the wires going to it. I already tried unplugging it and it didnt make a difference. Thanks
,

Ya, not happy, "imperfect", but that's life I guess.

... Anyway; did no 2 plug appear too clean (as if it was ingesting coolant); if so, would recheck/snug/torque all the intake bolts as there's a coolant crossover passage beside no 2 intake port (watch/feel for anything abnormal here; including how all the bolts feel/respond/move etc).
... On a side note; the pass side rear coolant passage in head that is blanked/blocked off by intake seems to be a common area for seepage, and sweating bolts (and broken stock TTY bolts) on many engines.

... Just a novice at this stuff; but both codes show high voltage which is normal when rich; did by any chance the dizzy get turned/moved and now fuel sync for injectors is way off???
... Helpful to mention what all the plugs looked like, or were they all the same, "rich"?
 
#8 ·
Cyl 2 was covered in black soot. All plugs except 5 and 7 had that black soot coating. I'm pretty sure i didnt move the distributor, unless the hold down clamp is loose i dont think that happened.
There's another blocked coolant passage beside paired intake ports 7,5.

... Injectors ohm tested ok: but are all 8 injectors known/proven to be good and correct? (some have pulled their hair out and gone half near crazy over E-Bay injectors!!)

I reset the pcm by unhooking the battery. Whats the hard dump?
As Moparite said, do the hard dump; it's below the blue line.
... When reconnecting positive cable, unsure exactly what it means when it says: "Careful, no sparks now"; safety connotation aside, I'm assuming it may also mean cable should only contact batt post once and remains in contact (circuit to PCM etc is completed and remains completed, not broken); in other words, lineup cable with post and then "stuff it on post in one stroke" to avoid breaking circuit (sparks). ... Hope I'm not overthinking this.

=============================================
From a past DT thread...

You can do what is often called a "hard dump".

We (techs) often do this when we need to totally reset the ECU and either don't have the proper tool close by (too lazy to walk to toolbox and get it) or just are "in a hurry".

First, disconnect positive+ battery cable at the battery and ground it to the chassis. Yes, the POSITIVE CABLE.

Wait a few seconds, 30 won't kill ya.

Now reconnect the positive cable. Careful, no sparks now.

Get in the vehicle, turn ignition key to on (run) position, now depress fully and release the gas pedal 5 times to set the TPS to WOT. (Make sure the floor mats do not keep the pedal from going WFO)

Turn the key to off, wait a min, and you should have cleared everything in the ECU except for the factory programming.
=============================================

The hard dump does not effect the (factory) alarm, the only thing I noticed is my radio presets, as this method came from a working Chrysler tech, I doubt if there are any negative effects.
=============================================
 
#9 ·
I tried resetting the pcm doing the hard dump method. Like usual the truck ran fine until it went into closed loop. Then it started bucking at light throttle, and idling bad. Check engine light came back on. 4 codes showing now. P0132 rich sensor 1, P0135 heater circuit malfunction sensor 1, P0138 rich sensor 2, P0141 heater circuit malfunction sensor 2.

I have already replaced the precat o2 sensor twice because of the heater curcuit. After the second sensor i decided to check the first o2 sensor's heater circuit (should have checked it first but i didnt know how) and it had continuity. The two sensors had a different part number but the second sensor is from the dodge dealer. I have also tried unplugging the front o2 sensor but that didnt make a difference. Does anyone know how to test an o2 sensor with a multimeter? Or any other suggestions? Thanks
 
#10 ·
i decided to check the first o2 sensor's heater circuit (should have checked it first but i didnt know how) and it had continuity.
Continuity to where? Are you checking across the pins on the 02? You need to check if you have a ground and 12V(+) going to the 02. 02's need to heat up by supplying voltage12(+) and aground to them. This helps them get up to operating temp fast so the pcm can get an accurate reading. You will need a wiring diagram to identify the wires going to the 02's
 
#11 ·
Yes i checked across the white wires on the o2 sensor. I have a factory service manual but i'm having trouble finding which is power and ground. Do you know what each wire is for? Also do i need to check it with the truck running? I put a test light on the o2 sensor fuse and it is only getting power with the truck running. I also noticed there is spots in the pdc fuse/relay box under the hood for o2 sensor heater relays. But when i put a relay in those spots they didnt clip into anything. Is that how these are on gas engine trucks? Its always been like that since i got the truck and i wasnt having o2 codes except p0420 because the cat is gutted. I was told to check out the tps, try unplugging it and see if the problems go away. To me that seems like it would cause more problems and the pcm wouldn't know how much fuel to put into the engine because it wouldn't know how much the throttle plates are open. Does that make sense?
 
#12 ·
If you have the factory manual all the wiring is in it. look up your configuration(5.2 5.9 v10 etc) in the wiring section and find the 02 sensors. There should be dark letter/# like C385 (for example) by it. Look this # up in the pin out section and it will tell you what every wire is. As far as i know all the second gens use the asd relay to supply voltage to the heater side of the 02's. There may have been some changes among the years with Cali emissions(four 02's). All of this will be in there.
 
#13 ·
Ok thanks. I wasn't sure exactly how they had everything in the fsm. I noticed something about the new pcv valve i bought from the dealer. I can blow air through it both directions. One way is more restricted than the other but i can still blow air through it. The old on from napa only lets air through one way which is how i thought they worked. Is the new pcv valve from dodge no good?
 
#14 ·
For 98, PCV valve should rattle when shaken; FAIK should not be able to blow backwards thru it, unsure (some earlier dodges had fancy spring types).
 
#16 ·
Doubt it, vac is high at idle so there will be constant flow thru PCV valve; at idle, pull it out of valve cover; it should be hissing and vacuum can be felt at hole in bottom of valve.
 
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