DodgeTalk Forum banner

Status
Not open for further replies.
1 - 15 of 15 Posts

·
Beard's coming in nice
Joined
·
8 Posts
Discussion Starter #1
Hi all,

My apologies if this should not be a new thread, or if it is in the wrong section.

I have a 1998 dodge ram with the 5.2, and about 195k km. It is not running very well. I have done some research as to what it could be, and I have narrowed it down to either a bad plenum gasket or a clogged cat.... or both!?

The symptoms I am experiencing are as follows:
-VERY loud hissing noise coming from the engine bay. (haven't pin-pointed the source)
-Misfire under idle.
-truck wont rev past 1600rpm when parked, and very little power when actually driving it, which has gotten to the point where it's not driveable on the street.
(I removed the o2 sensor before the cat and took it for a drive. No difference in power)
-Doesn't seem to be burning too much oil. Oil levels are still good.

I did remove the airbox and look down the throttle body into the plenum. I do see some oil residue, but none of this oil pooling that people say is associated with a bad plenum gasket. (i am assuming this residue is normal because of the PCV lines)


Any input would be greatly appreciated! :grin
 

·
Registered
Joined
·
4,137 Posts
IIRC, very loud hissing is caused by bad 02 sensor, unsure; would check for codes. ... Plenum "appears" to be dirtied quite a bit by PCV (pooling oil is often at rear as engine tilts lower at rear when truck is parked level).
... And the state of tune is?????
 

·
Beard's coming in nice
Joined
·
8 Posts
Discussion Starter #4
IIRC, very loud hissing is caused by bad 02 sensor, unsure; would check for codes. ... Plenum "appears" to be dirtied quite a bit by PCV (pooling oil is often at rear as engine tilts lower at rear when truck is parked level).
... And the state of tune is?????

What about the rpms? Any difference? Might want to check the fuel pressure also. Any codes? Do you have a lot blow by? I'm surprised you made it to almost 200k with the original plenum.
Thanks for the responses guys,

After doing my research, im surprised the truck made it this far on the original plenum as well, haha! My uncle mostly used this truck only for holiday use (highway driving while pulling a trailer) so the lack of heat cycles might have contributed to preserving the plenum gasket. He never used the truck to commute.

My buddy was driving the truck when the issue started happening. It happened pretty quickly apparently, and threw a CEL. Only code was P0302 Cylinder 2 Misfire. Sounds like a symptom that could happen in either case.

I can shoot a video of the truck when it's running, and hopefully it could help somebody provide me with more insight.


Also what do you mean by "the state of tune"?? The truck is pretty much stock. The only performance mods (if you can even call them that) are a K&N air intake, and flowmaster exhaust which has rusted away :p
 

·
Registered
Joined
·
4,137 Posts
General condition/miles on cap/rotor/wires/plugs
 

·
Beard's coming in nice
Joined
·
8 Posts
Discussion Starter #6
General condition/miles on cap/rotor/wires/plugs
Oh lol,

AFAIK the spark plugs and wires were done fairly recently. Maybe 30,000km to 40,000km ago. I took a look at a couple of the plugs, one of which is in cyl 2, and they looked alright. No sure about the distributor, i will have to ask, or take a look myself.

Do these tend to go bad fairly quickly on these trucks?
 

·
Registered
Joined
·
5,210 Posts
If you got the one with the aluminum inserts instead of the brass then yes. If you have an aluminum one get a new (oem style) brass insert one. The aluminum corrodes. Check that the wires are firmly in the cap, Especially #2 .
 

·
Registered
Joined
·
4,137 Posts
If you got the one with the aluminum inserts instead of the brass then yes. If you have an aluminum one get a new (oem style) brass insert one. The aluminum corrodes. Check that the wires are firmly in the cap, Especially #2 .
X2

No sure about the distributor, i will have to ask, or take a look myself.

Do these tend to go bad fairly quickly on these trucks?
Cam Position Sensor (aka pickup coil) inside dizzy can cause issues, but its not your issue now).
..DO NOT turn/rotate dizzy or "fuel sync" will be messed up and cost you bucks to get reset! (PCM controls all ignition timing, nothing you can adjust with timing light etc).

... Being truck was just used for holidays etc, perhaps old fuel (ethanol :frown) has messed up no.2 injector (definitely rule out all things ignition first).
 

·
Beard's coming in nice
Joined
·
8 Posts
Discussion Starter #9
X2



Cam Position Sensor (aka pickup coil) inside dizzy can cause issues, but its not your issue now).
..DO NOT turn/rotate dizzy or "fuel sync" will be messed up and cost you bucks to get reset! (PCM controls all ignition timing, nothing you can adjust with timing light etc).

... Being truck was just used for holidays etc, perhaps old fuel (ethanol :frown) has messed up no.2 injector (definitely rule out all things ignition first).
I will definetly check all the ignition stuff. It seems like a good place to start.:rck:

The hissing noise is quite the mystery. I took a quick video and uploaded it to youtube to demonstrate what it sounds like. It seems pretty severe. Could this be a blown exhaust manifold?? potentially as a result of a clogged cat, potentially caused by this misfire that happened out of nowhere :/

https://youtu.be/DE2Dp9LW7GY
 

·
Registered
Joined
·
4,137 Posts
The hissing noise is quite the mystery. I took a quick video and uploaded it to youtube to demonstrate what it sounds like. It seems pretty severe.

Could this be a blown exhaust manifold?? potentially as a result of a clogged cat, potentially caused by this misfire that happened out of nowhere :/

https://youtu.be/DE2Dp9LW7GY
... As said earlier, IIRC others with very loud hissing ended up having 02 issues.
..Sorry, kinda deaf, only heard rough running; but engine was cold in vid (open loop) so 02 is not a factor, but idle sure seemed very high, always over 1000.
..When fully warmed up (closed loop) what is idle rpm? (if it's high, maybe hissing/issues are caused by a major ish vac leak; check for missing vac cap/plug on intake, or line to brake booster, faulty TB gasket, orrrr)
..Could try the "finger trick" for IAC in post 12 of link

http://www.dodgetalk.com/forums/showthread.php?t=138174

... Doubt its exhaust issue but have been wrong before.
 

·
Registered
Joined
·
28 Posts
ya know key I too have allot of these symptoms wish there was a video of the finger trick. is it just choking out the aic valve when it tryed to open and suck all that vacuum in forcing the plunger to pull all they way back then resetting the pcm?
 

·
Registered
Joined
·
4,137 Posts
ya know key I too have allot of these symptoms wish there was a video of the finger trick. is it just choking out the aic valve when it tryed to open and suck all that vacuum in forcing the plunger to pull all they way back then resetting the pcm?
finger trick steps were laid out in Stevs? post/link; who knows, might be a vid somewhere, gooo
 

·
Beard's coming in nice
Joined
·
8 Posts
Discussion Starter #13
I will definitely check for the finger trick. Thanks for the heads up!

Thats not the truck idling. The truck has been sitting for a while. Normally after it has sat, the truck will forget how to idle, and it will stall out when i remove my foot from the gas. I usually have to run it while controlling the throttle for 5 minutes or so before the truck remembers how to idle again.
 

·
Pin it to win it
Joined
·
1,279 Posts
I will definitely check for the finger trick. Thanks for the heads up!

Thats not the truck idling. The truck has been sitting for a while. Normally after it has sat, the truck will forget how to idle, and it will stall out when i remove my foot from the gas. I usually have to run it while controlling the throttle for 5 minutes or so before the truck remembers how to idle again.
Sounds like your problem is in the Throttle body somewhere, either the gasket to the TB has gone bad, or the sensors on it are failing. There should be a rubber piece of hose on the front of it, see if it has a hole, I can hear the hissing, and it sounds like a vacuum leak to me. Easiest way to find out, spray brake clean, if the engine reacts to it, you got a leak! don't spray it down the butter flys try to spry under it and around it, if any gasket has a leak it will suck it in and you'll hear the engine rpm rise. As far as the cat if you think its clogged just remove the sucker, unless you live in a state that checks for emissions.
 

·
Beard's coming in nice
Joined
·
8 Posts
Discussion Starter #15
Sounds like your problem is in the Throttle body somewhere, either the gasket to the TB has gone bad, or the sensors on it are failing. There should be a rubber piece of hose on the front of it, see if it has a hole, I can hear the hissing, and it sounds like a vacuum leak to me. Easiest way to find out, spray brake clean, if the engine reacts to it, you got a leak! don't spray it down the butter flys try to spry under it and around it, if any gasket has a leak it will suck it in and you'll hear the engine rpm rise. As far as the cat if you think its clogged just remove the sucker, unless you live in a state that checks for emissions.
I actually dropped a dentists mirror into the throttle body while i was looking for oil pooling in the plenum. Therefore i had to remove the throttle body to retrieve it, hence I have a new throttle body gasket :D

Developments on this story have been slow, since i haven't really had the money, nor the resources to pursue this issue.

I boosted the truck a few days ago. Now that it is warmer out, the truck has been able to idle on its own.

You can hear the hissing noise from a good distance away. You can hear it pretty clearly from under the truck.
https://youtu.be/jjmx9B8cRLc


I took a look underneath the truck while it was running, and i noticed that one of the flange in one of the downpipes before the cat seems to be leaking a bit.


Seems to be pointing towards a clogged cat. Why else would this exhaust gasket be blown.

Gotta find a vacuum gauge and test the back pressure levels in the exhaust...
 
1 - 15 of 15 Posts
Status
Not open for further replies.
Top