98 Ram problems

[Sungazer]

Within a few months of buying my 98 Ram 5.2L (used in 2001) it started running poorly.

The symptoms:
- poor acceleration
- exhaust smell
- downshift on very slight inclines
- slowly getting worse

What I've done:
- replaced spark plugs, wires, coil, cap & rotor (this helps for about 3 days)
- injection system cleaning
- 3 or 4 shops claim catalytic converter is fine
- replaced downstream O2 sensor (it coded in mid-2002)

Any suggestions would be welcome, but I'd like to figure out what is wrong with it before spending too much more money it. I do have access to a laptop and AutoTap for reading the sensors. I don't really know what the sensor readings look like on a properly operating vehicle, though, so it's not much help to me at this point unless there's a fault code.

Thanks in advance!

[04HemiBeast]

How many miles are on the truck?
If the cat is original and high mileage it still
may be the problem. What do you mean when
you say the exhaust smells?? A sulfur type
odor is a good sign of a bad cats. The cats
on Dodge trucks flow quite well but don't last
worth a damn. Mine went out in 35K miles.
You may want to change the pre-cat 02
sensor. It tends to build up more carbon
that the post-cat sensor. It can still effect
performance even though you may not get
a check engine light.

[spirit-dodge]

When was your last tranny service and was it at a dealer/tranny shop or an instant oil change place? Is your tach jumping 200 RPM when the cruise is on? If your driving a steady speed(55) and increase to 70 with normal gas padal depression does it not respond and all of the sudden it kicks down and goes? Ok I ran out of Questions!

[Sungazer]

Thanks for the responses.

To answer the questions:
- the truck has about 87k on it now
- I got the truck at about 45k and have not replaced the cat (I don't know prior to that)
- the smell is of sulfur, and is strongest after driving for a while
- the last tranny service was about 15 or 20k ago at a dealer.
- there is no change in the tach while on cruise, except when it downshifts
- even the slightest gas pedal depression will make it downshift. It will make a lot more noise, but not accelerate much faster.

I warmed it up yesterday, then plugged in the AutoTap to look at the O2 sensor readings. I'm rather confused by what I get. The readings that show up as non-zero are O2 Sensor 1/2, O2 Sensor 2/1, and O2 Sensor 2/2. 1/2 varies between 0.1 and 0.9 volts like I'd expect, but it is rather eratic and spends most of the time above 0.6. 2/1 and 2/2 both sit at about 4.6 volts and don't really vary much at all (less than 0.05). If these are true readings I would expect to see a trouble code from the PCM. Maybe AutoTap is not reading them correctly, or maybe the PCM is bad, or maybe it isn't supposed to give a code so long as it reads something - I don't know.

I am considering replacing the cat and the O2 sensors, but I'm a little hesitant. That's a lot of money to spend if it is not the problem. I have wondered about the transmission, but it doesn't seem to fit the symptoms I read for bad transmissions. Basically the truck feels like something is holding it back - like I'm dragging my house behind it everywhere I go. I think I'll try to find some time to do a physical check of the O2 sensors next weekend, and maybe drive without the upstream one in to see if the release of pressure helps any.

Thanks again for the replies.

[Big Blue]

I would have to agree with the "bad cat" theory. I had the same problem on a Ford I used to own. Stinky exhaust and lack of power due to a blockage in the cat. It finally got so blocked up that the car wouldn't run anymore......the ol' banana in the tailpipe situation.

Can't say for sure if that's your problem, but the symptoms are the same.

[KellerSS/T]

When my cat went out the smell was very strong also. Upon startup does your exhaust make a rattling sound? The honeycomb inside my cat actually broke away from the walls when it went out.

[Sungazer]

Replaced the cat and both O2 sensors. I don't notice much difference, but my wife claims it's a little better. It still downshifts at the slightest tap of the accelerator and doesn't provide much acceleration. I didn't notice a smell anymore, but I bit more concerned about the performance and gas mileage than the smell! Autotap shows the same readings on the new sensors - I don't know what to make of that. Is it possible the muffler could be restricting the exhaust flow enough to make it behave this way?

[wh22366]

Did the material that broke up in the cat migrate into the muffler? It's happened to me with several cars/trucks.

Is your truck burning oil? If it's a symtom you didn't mention, it's possible you have a leaking plenum gasket under the intake. Take a look down through the throttle bores for an oil puddle -- that'd foul up a cat in a hurry. :)

[rob_ryche]

sungazer, something you can also check, is your plenum gasket. with the enging off, just remove your air cleaner cover that sits over the throttle body, crack the blades a bit and look down inside with a flashlight, if you see alot of oil at the bottom of your intake, then ur gasket blew out. that's a common problem on our engines, and it will cause a decrease in performance as well because of all the oil getting sucked into the combustion chambers. i finally had the chance to replace mine about 2 weekends ago, and it's running much better now.

[AlaskanRam]

Are you still having this problem these days? Well i had a few of your problems recently, bad accelaration and plenty of uneeded downshifts. Heres a question: did the prior owner throw in a K&N air filter, or any aftermarket drop in filter? It turned out for me that the one that was in my truck was very very dirty and restricting. I had my truck serviced on many occasions prior to this, and i think what may have happend is that once the technician cracked open the air box and saw a K&N, he knew that a new air filter (what you would get in a regular tune up) would not be nessary and he just left it alone. Well i suffered through some bad gas milage and poor acceleration before i decided to check it out, and then bought some filter cleaner by K&N. $11.00 and about an hour a had a brand new looking filter, and it flowed like it too. Power was much better, and the tranny didnt need to downshift as much because it had much more power to work with. Its sounds like a simple thing after all your advanced computer read-outs and what not, but just make sure at least...

-Jason-

[Poisonous]

I would guess plenum and cat right off the bat. Went through everything you stated above last summer. If you can fix it yourself, its cheap repair. Ordered my cat from ebay and had it put on locally for $30. Was easy to do the plenum, considering i never opened a motor that much in my life.

Hope it helps
Check your oil, if its drinking it like water, its definately the plenum

Poisonous :rck: