'96 Ram 1500 4x4, 5.2L, 5 speed. Previous Owner told me that there is approx 30K miles on a rebuilt engine, with an RV cam. Of course, I didn't get any documentation to prove it one way or the other...and the PO could have said anything...I've also noticed that the throttle body has Holley cast into it on the top...I've read that Holley made the TBs for Dodge for these trucks, but I don't know if this is one of the aftermarkets or stock.

Anyways, I've recently noticed that oftentimes when I come to a stop, that the engine idle will drop low, causing the oil light to come on. So far, I've only seen it on a warm engine. Even with the idle isn't dropping enough to illuminate the light, it still seems like it's idling low. I haven't had a chance to get a proper tach on it, but going by the factory tach, I'm guesstimating it's idling at rougly 600-650rpm. It's generally sitting a needle's width under the thin line before the number 1.

It seems to be worse if I let the throttle snap shut from 2500+rpm....it then often will go down to less than 500rpm, causing the light to go on and the gauge to go to 0, but as soon as the rpms recover, the gauge snaps back up to 40, and the light goes off. If I let the throttle close slowly, the idle will start around 1,000rpm, and slowly drop down to the "normal" idle (the 600-650 above), and if I let it sit long enough, it will drop just a hair bit more, illuminating the oil light. If I so much as just barely tap the throttle, the light goes out, but as soon as the idle settles down, the light comes back on. I've also noticed that about 50% of the time, the light comes on, but the factory gauge still shows approx 40psi. I also noticed that when the coil died, and I was just cranking the engine without it starting, the oil pressure did come up to about 20psi or so just on cranking speed alone. Oh, and if I try to hold the idle speed up with the gas pedal at a light, say right at 1,000RPMs, the speed will oscillate between about 900 and 1,100 RPMs, constantly and smoothly going back and forth.

I've recently changed the oil, putting in approx 5 quarts of Castrol 10W-40, with new Bosch filter, didn't seem to have an effect one way or the other, nor did replacing the failed coil. Check engine light is on, indicating problem with post-cat O2 (that sensor isn't installed at the moment). No other codes being shown (checked with scan tool). Also changed cap/rotor and spark plugs when I changed the coil.

 

failing TPS, or IAC could be the cause. although what yoru describing sounds like your oil pump is failing further testing would be needed.

 

I have experienced this also, I find it happens toward the 3000 mile mark since my last oil change, my local auto parts store gives a free fram oil filter away with the purchase of regular oil, and a fram toughgard oil filter away with a synthetic or synthetic blend oil purchase. I have always run valvoline maxlife and taken them up on the free filter until recently. I now buy the k&n oil filter and this doesn't happen at all ever anymore.

 

sounds like the pick up tube is clogged, and when you come to a stop the pressure drops anyways but with a clogged tube it can easily prevent flow., and when on the gas theres alot of pressure so it keeps the PSI.

 

i would check that idle control valve. sounds to me like it might be gummed up and sluggish to respond. I run castrol oil and a fram filter, my pressure never drops below 40 even at a 650rpm idle

 

Well there is no doubt about it, you have a plenum blow out. The same stuff was happening to my truck- oil pressure dropping, low idle, using oil, ect.. you need to replace your plenum gasket and this will solve your issue, its a common problem among magnum engines. It will cost you $650 @ the dealership to replace the gaskets, new o2 sensors and labor and all that crap. Or if ur handy you can change it youself with a Hughes Plenum kit for under $200. Heres the link, hope this helped!

http://www.hughesengines.com/Index/p...5&partid=22220

 

Heh....I was just reading about that a few minutes ago, then the email came through notifying me of this reply. Good timing

Not that I'm at all trying to be a cheap-**** about this, but it is really necessary to do that upgrade on a basically stock engine that doesn't get run hard? From Hughes description, it sounds like it's intended for modified/boosted engines.

I have zero concerns about doing the work myself, as I've always done all my repair/maintenance work on my own, plus built half a dozen cars from scratch..I think I'll be OK there I'm looking at Autozone's website now, and they have the Felpro MS95392 gasket set, that looks like it includes the plenum, pair of intake to head gaskets, and the strip gaskets that go on the front and rear of the intake to block. The set is less than $18.

I left the truck at my shop, so I can't go check it now to verify what else I would need, so...will I need to pull the valve covers to pull the intake? Some sites I'm reading over are also saying that I will need to pull the distributor? I'm not at all looking forward to that, given how much of a PITA it is just to get the cap off, lol.

 

valve covers and distributor do NOT need to come off for this job. Yanking one of the valve covers might make it a tad easier to get the intake out. Not sure on that yet. (I get to do this job soon....)

You can replace just the gasket for the plenum plate, but, you can then look forward to doing the job again. The steel plate, against the aluminum intake, guarantees that it will happen again. spending the extra dollars on the hughes aluminum plate means, do it once, and you are done with it.

Get the plate, and install kit from hughes, or APS, you CANNOT reuse the intake manifold bolts. Hughes install kit includes them. (along with the intake gaskets)

 

Disty doesnt need to come out, valve covers can stay in place.

No, you dont need it, but if your replacing the gasket, do the hughes kit, because steel plate on an aluminum intake, IT WILL blow out again, so youre better off buying the hughes kit, and being done with it.

also i would say 90% of these magnum engines oil consumption is caused by the plenum gasket being blown out, so in the long run the hughes kit will save you money.

 

I just went through the same symptoms with the oil pressure, plus oil loss, oinging etc. Just had the plenum gasket changed with the hughes kit but now the oil pressure is worse, the oil seems watery and the coolant is dirty. Head gasket?