Rough Idle w/Low Oil Pressure?

Skyjay · Post by **Skyjay** » Wed Jun 09, 2010 11:10 pm

Hey y'all! first I'd like to say thanks for such a huge volume of information guys, it's helped me keep my '00 neon running like a dream through a cross country hike, and several trips up the CA RT1. However I've run into a problem that seems to have a number of causes, so i'm looking to see if I can't get some insight.
This is on a '00 Dodge Neon ES, 127k

When the engine is cold, the car runs fine at idle, no problems.
Typically when I come off the highway (and the engine temperature has warmed) car seems fine until I get to a stop light, or in traffic, whathaveyou. Car idles low, RPM drops to about 850, and the engine feels rough, then I get an oil pressure light. Tapping the throttle kills the light, but it'll come right back after a second. I don't get the indication at any engine speeds. Though I have noticed the engine runs a little rough at other RPM's (and have noticed the engine bucks when I get off the Accelerator, almost like if somebody came off the clutch too quick.

The oil pressure light only came on after I changed the oil last (used the Wally world high mileage brand, and I am none too impressed). Oil levels are fine, and I don't have any leaks (aside from the valve cover gaskets). Now this happened right after I changed the oil. But would sh**ty oil cause rough idle? RPM drop?

My probable list stands at
Carbonized throttle body
Failing oil pump (not likley)
Bad Wires
Bad Plugs (Both wires and plugs changed about 80k miles ago...hmmmmmmmmm)
Dirty fuel injectors
Really crappy oil (loses viscosity under heat?)
Idle speed adjusted too low

Any thoughts guys?

glasswars · Post by **glasswars** » Wed Jun 09, 2010 11:12 pm

Auto or manual?

Skyjay · Post by **Skyjay** » Wed Jun 09, 2010 11:26 pm

OH sorry, MTX

glasswars · Post by **glasswars** » Thu Jun 10, 2010 7:28 pm

Have you tried cruising on the highway and throwing it and neutral and seeing what happens?

Post by **occasional demons** » Thu Jun 10, 2010 7:47 pm

It shouldn't run too rough/shake at 850 rpm, nor should the oil light come on. I would look to the filter as a potential cause.

Oil is oil as far as pumping is concerned. If it is a thicker viscosity than you normally run, it might make a difference. Thicker oil is harder to pump. If the clearances in the oil pump are getting out of spec, it may have a harder time pulling it from the pan.
But again, if the filter was also changed with the oil, I would try another filter first. If that doesn't change it, then replace the oil sender. They are a fairly common fail. (but usually they seep oil also)

Clean the IAC motor, and the TB. Only use a soap based cleaner on the plastic TB, not Carb cleaner. Definately give it some fresh wires, spray some Mopar Combustion Chamber Cleaner per instructions on the can, and then install the new plugs.

ZeroChad · Post by **ZeroChad** » Thu Jun 10, 2010 7:54 pm

This is why every car should come with an oil pressure gauge. I''m not sure how you'd diagnose it other than to hook one up. Being RPM related does support the oil pump theory though. With higher rpms, the more pressure its putting out.

You mean 8k on the plugs right? The idle adjustment screw is on the throttle body underneath the throttle cable pulley.

Post by **occasional demons** » Thu Jun 10, 2010 8:01 pm

I tried adjusting the idle stop on mine. All it did for me was to cause the coasting idle to go to 1500+ rpm, instead of 1000. Mine habitually idles below 850. Sometime it will idle at 850, but it is rare. The trouble with the idle adjustment screw, is it also moves the TPS. I am too lazy to experiment with a vacuum bleed, or drill the throttle plate. One would think with a 60mm TB, a low idle wouldn't be a problem.

Skyjay · Post by **Skyjay** » Thu Jun 10, 2010 8:03 pm

glasswars wrote:Have you tried cruising on the highway and throwing it and neutral and seeing what happens?

I have and it seemed normal.

occational demons wrote:It shouldn't run too rough/shake at 850 rpm, nor should the oil light come on. I would look to the filter as a potential cause.

Oil is oil as far as pumping is concerned. If it is a thicker viscosity than you normally run, it might make a difference. Thicker oil is harder to pump. If the clearances in the oil pump are getting out of spec, it may have a harder time pulling it from the pan.
But again, if the filter was also changed with the oil, I would try another filter first. If that doesn't change it, then replace the oil sender. They are a fairly common fail. (but usually they seep oil also)

Well I did some investigating. I decided to change my oil firstly. Turns out the oil that came out was like water. I'm thinking the oil broke down somewhere, and it's only been about 2k since my last change. Lemme tell you I am NOT buying wally-world crap again, back to Castrol for me! Changed the Oil filter as well (Always fram).
Oil Pressure light and roughness seems to be fixed! so I'm guessing it was a chemical breakdown of the oil when it would become hot.
Though I did notice that my spark plugs were COVERED in oil. So my next step is to change out the valve cover gasket (I had to burn out the oil that fell into the cylinders), then the plugs and wires. Apparently my No. 3 Cylinder plug wire has started to degrade from the inside (possibly due to oil contamination). The plugs themselves weren't terrible, but had started to oxidize somewhat on the plug end.

I'm thinking at this point, after all the new hardware should perhaps seafoam the engine and hopefully this will clear the rest out.

I wish we didn't have dummy lights in cars, in aircraft whole different story! Been thinking about installing an oil pressure gague, perhaps at a later time.
I have about 32k on the plugs.... christ, it can't have been that long!

fixitmattman · Post by **fixitmattman** » Thu Jun 10, 2010 8:26 pm

If wally world oil was a problem, I would have found that by now. I would suggest other problems.

heydockyle · Post by **heydockyle** » Thu Jun 10, 2010 8:48 pm

fixitmattman wrote:If wally world oil was a problem, I would have found that by now. I would suggest other problems.

x2

Skyjay · Post by **Skyjay** » Thu Jun 10, 2010 11:18 pm

fixitmattman wrote:If wally world oil was a problem, I would have found that by now. I would suggest other problems.

Well, I'll monitor it and see what we come up with. You may be right, but to be honest i've never seen warm oil that thin.

gtxtreme19 · Post by **gtxtreme19** » Fri Jun 11, 2010 12:32 am

Skyjay wrote:Well, I'll monitor it and see what we come up with. You may be right, but to be honest i've never seen warm oil that thin.

Wait... in my experience warm oil is less viscous than cold oil and it typically "expands" like and gets thinner.

I could be wrong

Post by **racer12306** » Fri Jun 11, 2010 7:15 am

Unfortunately your fingers aren't calibrated to test viscosity of a fluid.

It's not the oil, I promise you that.

I would check into the filter due to Fram's quality issues. Many people use Fram's and don't have a problem, but others have a lot of problems. It's a cheap thing to try, should only cost $4 for a new filter.

Skyjay · Post by **Skyjay** » Fri Jun 11, 2010 12:33 pm

I'm starting to think the two problems may be unrelated.
As far as idle RPM it dosen't seem to drop as far as it has in the past. Once it gets below RPM the oil pressure light beeps on which I think is below spec (this happens when I induce load on the engine at idle, Ac compressor on).

given the condition of my ignition hardware I don't think a trip to the auto parts store would be harmful.

Got free time this weekend, lets see how it goes.
Thanks for the input guys!

fixitmattman · Post by **fixitmattman** » Fri Jun 11, 2010 9:24 pm

Skyjay wrote: Well, I'll monitor it and see what we come up with. You may be right, but to be honest i've never seen warm oil that thin.

Depends on grade and temp. If my engine is quite warm and it's warm out, and I've just done a lot of driving, my superamazing walmart oil spectacular 5w30 comes out just like water. When it's cold, not so much. I can say almost for certain it's not breaking down, it's just warm.

Post by **racer12306** » Fri Jun 11, 2010 10:25 pm

fixitmattman wrote:
Skyjay wrote: Well, I'll monitor it and see what we come up with. You may be right, but to be honest i've never seen warm oil that thin.
Depends on grade and temp. If my engine is quite warm and it's warm out, and I've just done a lot of driving, my superamazing walmart oil spectacular 5w30 comes out just like water. When it's cold, not so much. I can say almost for certain it's not breaking down, it's just warm.

He's also never seen hot 5w20.

It's not the oil, I promise.

Skyjay · Post by **Skyjay** » Thu Jun 17, 2010 3:03 pm

Damn fram, turns out it was the filter (I nabbed another bottle of the wally-world brand to check).
I've never had a problem with fram, and i've been using them for 10 years now!

Okay, SO....going from here I want to swap to synthetic oil and perhaps a larger capacity oil filter.
Stupid question the first: Do I need to do anything specific to changeover to synthetic, like change first oil in 1000 miles or something?

Stupid question the second: Is a larger-capacity oil filter a GOOD idea?

Final stupid question of the morning: Should I change my valve cover gasket after draining oil out of the crank case?

Thanks again guys, I am humbled in the presence of your answers.

eastwoodsn352 · Post by **eastwoodsn352** » Thu Jun 17, 2010 3:09 pm

you're not suppose to change from conventional to synthetic on a high mileage engine from what I understand.

Post by **occasional demons** » Thu Jun 17, 2010 3:45 pm

Skyjay wrote:Damn fram, turns out it was the filter

.
Stupid question the first: Do I need to do anything specific to changeover to synthetic, like change first oil in 1000 miles or something? No today's synthetic is 100% compatible

Stupid question the second: Is a larger-capacity oil filter a GOOD idea?
Only if there are no clearance issues.

Final stupid question of the morning: Should I change my valve cover gasket after draining oil out of the crank case?
? not sure why you would...

Thanks again guys, I am humbled in the presence of your answers.
Someday, you too will be a neon expert.

Post by **occasional demons** » Thu Jun 17, 2010 3:46 pm

eastwoodsn352 wrote:you're not suppose to change from conventional to synthetic on a high mileage engine from what I understand.

The only problem that might occur, is that the synthetic will find the weak links in the seals. It only shows you where the leaks are, it does not create them.

Skyjay · Post by **Skyjay** » Sat Jun 19, 2010 1:10 am

the only reason I'm thinking of draining the oil during the valve cover gasket replacement is just to keep less oil in the picture while I'm working. Granted gravity should take care of most of the picture, but I figure it can't hurt, can it?
(also might help me have a better look at engine components. I've noticed there isin't a HowTo for the valve cover gasket, I know it's a simple install, but maybe I'll break out my tripod for this one.

Post by **occasional demons** » Sun Jun 20, 2010 8:53 pm

The valve cover/head will have the same amount of oil lying in there regardless if you drain your oil or not. With the engine off, all the oil is in the pan, that can drain there. (The oil does not fill the entire engine, if you were thinking that.)

If you are taking pics, you could soak up the oil lying in the head, if that's what you meant. There is a fair amount that is retained under the cam for lubrication at start up.

Skyjay · Post by **Skyjay** » Mon Jun 21, 2010 12:10 am

occasional demons wrote: If you are taking pics, you could soak up the oil lying in the head, if that's what you meant. There is a fair amount that is retained under the cam for lubrication at start up.

Sounds like a fair bit of work, I guess I'll have to take a look and find out!

Skyjay · Post by **Skyjay** » Sat Jun 26, 2010 10:11 pm

OKAY...so...
Oil changed to synthetic, mobile1 filter, new plugs, wire, and gasket.
Still the same problem with the low oil pressure.

When the engine is cold, engine idles fine, no warning light.
When the engine is warm, and I have kept RPMs low, engine idles fine, no warning light.
After I drive on the highway, engine idles a little rough, and the warning light comes on. When it does, it's any time the engine hits idle, so if I'm in traffic, really annoying. I am also getting a burning oil smell from my vents after the engine has idled with the oil warning light on. Once engine RPM's are over 1100, oil light goes off.

Any clues folks?