Hi. I’ve been reading up on some old posts regarding the red oil light coming on during low rpms, usually when coming to a stop. The motor will bog up and down some with the chime and light. This goes away once the throttle is increased. Just recently had the valve cover replaced along with new plugs, exhaust, upper o2 sensor, and recent oil change. The light just started coming on before the oil change when the oil was down almost a quart. Light still comes on. I’m not getting any fault codes with a cheap scanner as expected. I’ve read several possibilities but didn’t know if this has been pinned down to a more common problem and repair. Any new updates? Thank you!

 

First thing is to check the oil level and if down top it up. Do not overfill but my SOP is to regardless if the engine requires 5 quarts or 9+ quarts of oil to run the oil level at or close to the max full level.

A too low an idle speed can result in a low oil pressure light. Chances are the condition that cause the low idle speed is the problem. The low oil pressure arises from the low RPMs.

To state the obvious idle RPMs going up and down is not normal. Had another car manifest this behavior two different times. First time was from what proved to be a bad air/oil separator (AOS). It had failed and was subjecting the crankcase to full intake vacuum. This was to some degree an intake air leak with air coming into the intake after the MAF so it was unmetered air.

The 2nd time was when what proved to be a bad variable valve timing system (solenoid/actuator) went bad. In this case the RPMs varied enough that at their lowest level -- by the tach -- which is not a precise instrument -- of around 500 RPMs the low oil pressure light would come on. And as the RPMs climbed the light went off.

A general rule when a problem shows up out of the blue is last thing touched is first thing suspected. With this in mind my eyes instantly zoomed in on the new valve cover (and I assume a new gasket). The behavior suggests this is leaking.

A smoke test would likely confirm this one way or the other. Another way is with the engine idling and manifesting the up and down idle to spray carb cleaner (from an aerosol can) along where the valve cover bolts to the head and any hose connections. If there is a leak the engine will (probably) react. Unfortunately the leak is not like a true intake leak in which the carb cleaner has a straight shot so to speak into the engine. So the carb cleaner trick may not work even if there is a valve cover leak.

But the variation in idle speed could arise from a problem with the camshaft drive system: Worn/loose chain, weak tensioner.

To me job #1 is the source of that idle speed variation needs to be found and addressed.

 

Thank you so much for the info! Oil level has been fine since. It was just brought to my attention that it was doing this before the valve cover was replaced. The wife failed to mention that. Won’t hurt to try the carb cleaner spray. Yes, OEM valve cover, new gasket, and sealed at certain areas as documented. I might’ve chose the wrong words about the idle up and down. It runs great, doesn’t have the issue until we’ll after it’s been warmed up and driven for a bit. At that time is when the car slows to a stop then the idle starts to drop, motor starts to chug some, and the light comes on until you hit the gas.

 

Just to get this out there: An unstable idle, an idle that doesn't stay pretty much at the hot idle RPMs, is *not* normal.

An engine that manifests a drop in idle speed and after some engine run time this can arise from several possible reasons. An alternator that is not working right. Its output drops or the flip side is it is signaled to make more electricity and this loads the engine. Generally the engine controller is capable of compensating to keep the idle speed on spec but there is a limit. Absent a battery voltage gauge on the dash all you might have to available is a battery symbol that lights up. I have seen techs leave a car parked in a service bay with the engine idling and a volt/ohm meter connected displaying battery voltage to "catch" the alternator when its output starts to drop.

Yet another possible explanation is a fuel pump. In cars with direct fuel injection this is most often the low pressure fuel pump.

One has to be careful. On the surface a monitoring of the voltage level could show the voltage level dropping as the RPMs drop but this could be the result of the RPMs dropping. The ECU sheds load by dialing back how much power the alternator puts out. The dropping voltage is a side effect of the fall off in RPMs.

The fall in RPMs could be due to a fuel supply problem. But there could be other explanations. Really this is probably not a problem one can diagnose on his driveway. A professional tech's expertise will be required.

 

I recall the mechanic telling me that he removed and cleaned the vanos solenoid while they replaced the valve cover. He said they can cause some erratic idling when they get dirty. I’m not sure if he did both. Not sure if he swapped them. I really don’t want to just start throwing parts at it with uncertainty but it could be worth a shot replacing them before paying for a full diagnosis.

 

With another brand of car when the VarioCam (Vanos) was suspected of acting up the tech replaced both the solenoid and actuator of the affected cylinder bank.

Cleaning was not a solution.

In the case of the MINI I gather cleaning is a possible solution. But if one VANOS needs cleaning I would just assume the other one would too. A tech might clean the 2nd one -- depends upon how much extra labor is involved -- but if he didn't at least he should advise the customer that it would be a good idea to clean both and get the customer's permission.

After he should take the time to confirm both VANOS were working properly. If not then replacement is probably required and the customer advised of this.

 

I was told this only has one solenoid, which is the one he cleaned. Thank you for your help! I’ll start with this and check for any loose ends while I have things pulled out of the way. If it continues then I’ll be off for a diagnosis.

 

Well yeah, if only one VANOS then only one to clean. I was thinking there would be could be two. One for the intake cam and one for the exhaust cam.

Even with just one VANOS after the cleaning its proper operation needs to be confirmed. This in case the problem wasn't due to dirt but something else.