My first thread, so bare with me.
Just got this 94 dodge 1500 4x4 5.2L. It has 200k miles. And well, I've noticed a few things other than bad gas mileage. First, after 20 mins of driving, engine light comes on, then the oil pressure gauge comes on a few min after. Oil gauge will bottom out, then back up to 40psi, and flutter back and forth at lights until I give it gas. Then, the truck will start to run a little rough only at lower RPMs. Once I back off and give it gas, it'll jump up to 3k RPMs and run smoother.
A throttle issue? vacuum leak? I plan on replacing and cleaning a few things around the intake manifold as well as cleaning it out. Tips on that would be helpful!!

Btw, as I drained the old oil, noticed only about a quart came out... Not good..

I just changed the oil, filter, air filter, new PCV valve and hose. I bought a new oil pressure sending unit, but haven't installed it yet. I've read other post and this seems like a regular issue..

I should also mention, I have 36/15.5/15 tires, 8" lift, so my highway speed is not good, around 65 mph at low rpms. If it engages to a lower gear I can get up to 70+. Gotta be bc of the tires.

HELP!

 

Could be many things. IAC, TPS, plenum, 02 sensor, etc. You will have to get a code reader or go to a shop. Most shops will read the code for you for a price. Your symptoms are telling me you may have a leaky plenum among other problems. Take off your air intake, open up or take off the throttle body and look down with a flashlight. If you see oil there is a plenum leak. Wouldn't hurt to clean throttle body at the same time. I recommend checking oil level very regularly. Also, with those tires, you need to change your gears. 4.56 or 4.88 will work fine with highway speeds and in town. They are pricy but less pricy than a tranny rebuild.

Another thing to add.. There is always the chance the oil pressure guage is faulty. My old 95 ram had a similar fluctuating oil pressure guage. After checking everything, I came to the conclusion it was faulty. Drove it for 3 years like that. But let the pros chime in.

 

Yeah it'll be my first throttle body clean but I'll manage. Any links that are step by step might help. What is the IAC again?? I'll try and replace the gauge and TPS in a few weeks.
I tried the on, off, on, off, on with the ignition and flashed 35.
I think it's code for radiator relay.. Which the guy at the auto store said my yr doesn't come with an electric fan?? Not sure but my buddy has the OBD1 and I'll see what codes are flashing.
How much and where can I get the plenum?
It's just a gasket correct?

 

Here's a link to answer all of your plenum questions:

https://dodgeforum.com/forum/2nd-gen...um-thread.html

As for IAC (Idle Air Control), its behind your throttle body. Two screws, one connection and it comes out. Clean it with a parts cleaner (I used brake cleaner) and reconnect it. TPS ( Throttle Positioning Sensor) is located on the side of the throttle body if I remember correctly. This sensor cannot be cleaned and reinstalled but there is a way to check it. Use the search and you'll find it pretty easily.

A good tune up also may be the fix. When was the last tune up (02 sensor, plugs, cap/router, etc) Hard to say without an engine code. Don't forget to undo the battery before changing any sensors. This resets the PCM

 

Thanks for the help. I'll keep ya updated.
Looks like I have some work to do with this truck..
I have a fuel leak coming from the tank now. Looks like it from the connection on top.

 

A leak will beat the crap out of your gas mileage..... and these trucks don't get the best even when everything is right.....

 

UPDATE
Ok I found the gas leak. It was in the fuel hose just above the tank. Fixed it and all better now. I could tell a HUGE difference in driving already. I also installed the oil sending unit. Oil gauge seems to be ok.. The oil light is staying off and not bouncing up and down anymore.
I'm able to keep my speed on the highway now too.. Was able to keep low rpms and maintain my speed even up hills. (Normally it would downshift and run over 3k rpms).
I also cleaned the IAC and reconnected it. Not sure if anything changed but it was pretty dirty.
I checked to see if the plenum was already changed and looked down the TB with a flashlight and NO oil! Just a little dirty.
I also took a telescope magnet to see if it stuck to the bottom as the link said, it did. So I'm assuming its the original TB and plenum???

I'm still going to do more such as plugs/wires, dist cap, tps.

I still feel as there is a slight miss but I'm not sure, it's like a bumping shaking the truck. It's small but it's like a bubble in one of the back tires... It very well could be just a bubble in the tire.

 

Yup it's the oem plenum. I can't talk because I have the oem plenum but I would look into changing it. It WILL leak eventually. Keep watch on it. How's the truck running now? Better than before? As for the miss, it could be misfiring. I would start with the obvious tune ups if the truck is due for one (plugs, wires, cap, 02 sensor) and go from there.

If you plan on keeping the truck for any period of time, i still recommend changing your gear ratio for those tires. Your tranny will thank you and the added power alone is worth it.

 

The truck is running much better actually. So far so good.
I will do the full tune up and few more add ons.
Dumb question but if I were to do gears, tough job??
Or better off going to a 4x4 shop?

 

Yeah it's a pretty tough job. You can save at least $500 by doing it yourself. There may be a DIY thread on this forum. If you are pretty mechanically inclined then yes, it's possible.