98 ram 5.2 help needed

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rod7515

rod7515

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Ive bought a truck that I have another thread on. I was wondering if there are any members that have done work on a 5.2 from 1998 or similar. I did the plugs, wires, rotor, cap, dist pickup this morning and I still have a miss at idle thats very noticeable in gear. Once its off idle and above 2000-2500 RPM's it smooths out or at least seems to. I can rev the engine from 1500 and up and not feel the miss.
Now the truck has no brakes or tags or inspection so I cant drive it out on the road!
I did a compression test today before I changed the ignition parts.
Drivers side frt to back: 140, 150, 150, 150
Passengers side frt to back: 145, 150, 140, 150
I have not done a leak down test yet but will this week.
I guess I should also check the injectors. I do have a noid set. Do I just unplug one at a time while running to check them or do I check them not running?
The motor sounds good and does not have any tapping or motor noise.
I bought an plenum gasket set and have done some reading about the issues surrounding them, but havent gotten to replace it yet. I dont want to replace that gasket and still find a miss so Im thinking when or if I need to replace it I will I would do a valve job at that time.
This is going to be my towing truck so I need to fix it right, no corner cutting!
Yep I need your help with direction on this as Ive never done more than a tuneup on these engines.
Thanks Rod
 
Take a good hard look down the throttle body with butterflies open. If you see evidence of oil the plenum gasket 99% of the time is bad. The reason your smoothing out at higher rpm is that the vacuum is decreasing with the throttle open. At idle and just off the system is trying to compensate for the additional flow in to the intake system from the vacuum leak. Of course that's my opinion and how I would go about it. I had a 99 Durango 5.9 that started using oil misfiring etc. Didn't look too bad thru the TB but once I pulled it and sat it on my bench there was enough oil in it to make a royal mess dripping out of it. Others hopefully will chime in.
 
Lol funny , I have a low speed , misfire under load. I just changed the cap, rotor , wires , plugs, TPS , MAFS , IACV , O2S along with douching the TB and new gasket , and reset the computer, and it's still there , I have a feeling it's either an injector or fuel pump, although there was evidence of oil pooling down in the intake manifold.
 
DUbob, Thanks for the advice. I will look down thru the throttle body and see if there is oil. I have the air intake cover off. If I pull the plenum I think it would be smart to do a valve job as well? Ive read if you go that far you should replace the lifters. They say that the magnums use a roller system. Do they all 5.2 magnums have rollers or is it after a certain year?

73AbodEE, When you say new gasket were you meaning just a TB gasket or plenum gasket? Did you do a compression test or leak down test? Also when you say reset the computer what did you mean and how did you do it.
Thanks Rod
 
It took me a about 5hrs to change the plenum ,remove a broken bolt and replace the water pump. It's not bad and do yourself a favor and get the hughes intake plenum kit if you want to do it once.
 
rod7515 said:
DUbob, Thanks for the advice. I will look down thru the throttle body and see if there is oil. I have the air intake cover off. If I pull the plenum I think it would be smart to do a valve job as well? Ive read if you go that far you should replace the lifters. They say that the magnums use a roller system. Do they all 5.2 magnums have rollers or is it after a certain year?

73AbodEE, When you say new gasket were you meaning just a TB gasket or plenum gasket? Did you do a compression test or leak down test? Also when you say reset the computer what did you mean and how did you do it.
Thanks Rod
Click to expand...
The throttle body gasket. Any time you unplug anything or make changes you need to reset the computer. I take the negative battery cable off , turn the headlight switch on, turn the ignition switch on like you are trying to start it , then hook the battery back up.
I didn't do a compression test or leak down because it just started acting up a week ago. I drive this truck every day
 
Ive already bought a fel pro gasket set. Whats the big difference between the 2 sets. Somewhere I read if you dont replace the plate under the bottom of the plenum you should use bolts that are 1/4" shorter?
I do plan on doing a timing chain and gears as well as a water pump whie Im at it.
Rod
 
I didn't get into lifters or valves. I may have done the timing chain but that was a few years ago so not sure. My personal theory is that the intake is aluminum and the plate for the plenum is steel. Different expansion and contraction rates. Mine the gasket was pushed out between most of the bolts. I did use the hughes kit on mine. Engine at that time was at about 100k. The intake bolts are also a torque to yield application.
 
Interesting, I had the very same trouble that took forever to find the issue....
This was what I found in my situation, it may not be yours but worth a check and easy.
Pull the distributor and check the bushing for the distributor shaft pressed in the bock. What I found was the bushing worn so badly it caused the gear to wear out (the gear that rides on the cam and goes through the bushing and drives the oil pump. This wear was not noticeable just looking down in the block (except for gear teeth worn). Put a large screw driver in the slot on the gear top (where the distributor goes) and move it all over, check for slop. I found that misfiring and bucking at idle and under load was because this bushing was crap and caused the movment of the distributor and misfires....once I replaced the bushing, all was great once again! I also found oil in the intake (very common on these) as other have mentioned. I fixed that as well....but it was not what caused the issue I had nor did it fix it.
This took for ever to find an I have never had this bushing go away on any motors I have had. Well it's worth a check, easy and cheap as well!
 
marksmopar1, Your the first person that I have seen post that problem. I can see why that would have been so hard to find. What did you use to pull that bushing out and install a new one? Ive never done one of them while motor was not out.
Was the drive gear a steel or bronze gear? I know that with roller cams you are supposed to use the bronze gear. Do you know if your motor was a roller? Also so what year vehicle and was it a 5.2?
Thanks for that heads up.
Rod
 
Hi,
It was a 96 in a Dakota. Roller cam. I am unsure on what the gear was made of but it was so worn out because the bushing was sloppy that the gear teeth were like knife edges! I pulled the ditrib, then checked for slop with a large slotted screw driver by wiggling the gear, it was moving a lot. I then pulled the gear up and out and found the bushing completely worn out. The cam was ok, so i guess the gear was of a softer material. I replaced it all with factory parts. I bad a hook tool (slide hammer sota thing) and pulled it out. Tapped a new one in. There is a tool for all this. One thing, when installing the new bushing they say it must be reamed. The new gear drive will not want to slide in most likely as the bushing squeezes a bit. Google this to get a clearer idea. it fixed my issue...and it was something I would have never thought of I just happen to get pissed and start looking deeper into the issue. I had that darn distributor out many times looking in that hole in the block....just this one time I decided to go further and poof..there it was!
 
If I were you I would definitely replace the plenum gasket first, I have had alot of these trucks and they all need it sooner or later. If there is no noise, chances are the lifters are fine. Sometimes its better not to mess with things that aren't broke, so leave them alone unless you see something wrong when you have the intake off. You didn't say how many miles are on the engine, but I changed the timing chain on my 2000 durango 5.9 at 273,000 miles and it still would have gone further, for what its worth.
 
Moparman9, The truck has 183K on it. I read your mileage of 273K! Wow that makes me feel good about only being at 183K. Thanks for the reply.
Rod
 
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