Oil Pressure scare!

[Mudman]

Hey all,

Car is: '89 LS TII

Last week I was driving the Lancer around the city during a hot day, temps were up to just past the middle of the "normal" range on my stock gauge.

When I would idle at a stop, my oil pressure would drop the the very bottom of the normal range and the "check gauges" light would flicker on. If I gave it a bit of throttle to bump the RPM's up, pressure would rise and the light would turn off.

This was super concerning so I made sure to keep my pressure up at the stop lights.

Few days later, oil pressure had been good (as our days of been cooler). I did a coolant system flush and fill and drove her around a good while to fully heat cycle and mix my coolant. When I drove back home, upon idle, the oil gauge would then hover for a couple seconds and DROP all the way. Like the gauge was turned off almost. "Check Gauges" came on and if I hit the throttle, the gauge would jump back up to a normal range.

This scares me. I have a mechanical oil gauge on order and will be connecting that once it arrives to really get a reading pressure in psi. I'm thinking perhaps it's the oil sensor since I never heard any signs of poor oiling. No knocks, scraping sounds, etc.

I wanted to ask if you guys have come across an issue such as this. I'll post my findings over the next few days with the oil pressure gauge.

As long as the engine doesn't reach higher operating temperatures, the oil pressure remains normal even while idling. If the engine is not (thinning out the oil) that's when I get idle pressure issues.

Thoughts?

[Reaper1]

IIRC the minimum operating pressure at idle for a 2.2/2.5 according to the FSM is either 2 or 4psi. It's stupid low! On top of that, the "Check Gauges" switch that turns the light on has a higher threshold than that (I think it's 10psi). I have seen and had this problem happen to me before as well. Most recently on the 8V Masi. I found that there was oil down in the electrical connector, plus the retainer clip is broken off, so it tends to come out easily.

You are already getting a mechanical gauge, so that's good. I'd suggest popping the oil pan off and inspecting the rod bearings, just in case.

How old is the oil? What weight is it? What is the oil level? Is the oil contaminated?

I HIGHLY suggest an oil cooler! I have seen the difference between oil pressure at idle with and without one when living in Florida. I preach the oil cooler thing!

[Mudman]

I believe the lowest normal range is 4psi for these motors. Oil was almost a quart low when I noticed the pressure issue the first time. I straight parked the car and walked to the nearest autoshop and grabbed a quart. A little more background, I had the lady with me last week and we took a romp in the Lancer together. She likes going fast, I like people appreciating my car, it's a match made in heaven. Making several full throttle pulls 2-4th gears and diving into the corners to test all my late suspension work, we ran her pretty hard. Harder than I have in a while. I never revved past 4500rpm, and she performed beautifully, not a single misfire or complaint. However, I lost oil on that run. Excessive blow-by it looks like. Looks like I drained half a quart in the couple hours we were running around.


I normally run Mobile 1 5-30 full synthetic oil in the car, and it's never given me problems before. Current oil is probably still 1000 miles away from changing, though it does look "blacker" than normal for the amount of miles. Oil level is back up to full, and I have been checking it the past couple days, no visible loss since topping off. I've thought about going thicker as a bandaid for this issue but actually want to get some readings with the mechanical gauge on the current oil.

I'd rather not pop the pan unless I have to, mine has ALWAYS been a PITA to seal perfectly. If needed, I'll do it, I won't skip out on proper diagnostics, but only if needed haha.

[Vigo]

Well then you should probably do a compression test before doing anything else to the engine like resealing or even changing the oil. Might want to see if the bottom of your intercooler is full of oil too.

[going4speed]

If you have marked blow by you are fuel diluting your oil thus driving your viscosity lower than anticipated.

[Mudman]

Well then you should probably do a compression test before doing anything else to the engine like resealing or even changing the oil. Might want to see if the bottom of your intercooler is full of oil too.

Compression test is definitely on the "to-do" list. I'm working 12 hour shifts today and tomorrow and won't be able to drive out to my dad's shop until Wednesday, but I'll be doing that. This engine was rebuilt about 6-7 years ago and never had excessive blow-by issues before. Looks like it may have some problems with it now..

I did take the intercooler out and some charge piping off to inspect. Oil residue present, perhaps a bit more than a "perfectly" sealing engine, but nothing excessive. Just a little pool about the size of a quarter collected at the bottom-most point on the bottom IC connector and some oily residue in the charge piping (keep in mind this is after a couple years of driving without ever taking those parts off for inspection)

[Mudman]

If you have marked blow by you are fuel diluting your oil thus driving your viscosity lower than anticipated.

Aha, you make a good point here. I gotta say, that thought didn't occur to me as I only really drove her hard for one good session. I guess I didn't think that one incident of blow-by could thin my oil so much as to cause oiling issues. I will be inspecting the oil again after work tonight and smell for gas, etc.

[going4speed]

The blow by is a constant and not only a result of spirited driving. If you plan on just driving it top up oil with 20-50 instead.

[Mudman]

I closely inspected my oil, stupid me for not catching this sooner, but there is definitely gas making it into my oil. It was visibly thinned this time and smelled of it.

Being that these issues magically showed up after a very hard run, I think there's something potentially serious happening here, such as a cracked ring landing.

The Lancer is parked for now, I have Wednesday off so I'll get to tinker with it then. The oil is so fouled that I will be changing it and popping the oil gauge on there Wednesday.

This may not be the "smartest" way to go about things, but after the oil change I plan on taking her for a drive. Nothing risky but I want it to see moderate boost a few times, then inspect my oil again. If I can sense gas from a short moderate run, it's probably time to tear down the engine. A compression test will be done before as well, my dad's going to drop off the test gauge tomorrow at my house while I'm working.

[Reaper1]

Before you go on your drive, pop the fuel rail off, prime the fuel system and see if you have a leaking injector. Also inspect the vacuum line on the FPR and make sure it doesn't have fuel in it.

[Mudman]

Before you go on your drive, pop the fuel rail off, prime the fuel system and see if you have a leaking injector. Also inspect the vacuum line on the FPR and make sure it doesn't have fuel in it.

Good call, I was just looking into leaky injectors being one of the main causes of gas-in-oil issues (for not only TM cars, just in general). I've never actually messed with my fuel rail/injectors, they've stayed securely mounted to my intake mani whenever I was working around those components ha. Time to break out the Chilton manual and get a feel for it. I'm sure it's pretty straight forward.

[Vigo]

Being that these issues magically showed up after a very hard run, I think there's something potentially serious happening here, such as a cracked ring landing.

Thats exactly why i went straight to the compression check. Let us know what you find!

[going4speed]

I prefer leak down test

[Vigo]

Leakdown test tells you more but it's a lot more tedious and lot more sensitive to 'doing it wrong'. Plus compression is a reflection of leakdown, so if you have good compression you have good leakdown. Compression just doesn't tell you WHY something is bad when it's bad. That's where leakdown becomes necessary instead of just nice to know.

[going4speed]

yea I like the why