How long can you drive without oil cap?

[REKCUT]

50rpm drop indicates that there is an issue, your engine should be stumbling pretty hard or stalling out when you open the cap up. When you

So i guess its just a midwest kind of thing since you say you know everything there is to know about these truck. I realize i don't have your time or experience here on mud but i can read, and post after post are telling stories of their truck idling with no issues with oil cap off. As I'm from Missouri I have that "Show-me" mentality.

1. My truck runs with almost no change of idle with the dipstick out or cap off. It does die if i pull of the hose on the PCV valve.
2. The LX450 down the street is exactly the same. No issues with cap off or dipstick out. Dies if you pull the PCV hose
3. 96 80 in club is the same
4. 97 80 in club is same
5 97 80 anniversary of Zane's in KC is same
6. Club member in Republic Mo. runs the same
7. Buddy in Bentonville, runs the same

I have contacted 10 individuals tonight that I personally know and had them pull the cap and dipstick with no issues but shut down when PCV hose pulled. So either everyone of these trucks are broken, or you statement that truck will not run with cap off is wrong. I appreciate your first statement but to continue to insist that your version is absolute is and that you know everything a crock.

I ask these questions on here because you do get good help and there is a lot of experience, but it seems that lately you always have that one member thats condescending and a bit of a jerk. So while you may think your helping, your little links to " This is a PCV" and price of grommets is what makes these threads difficult to use.

 

[REKCUT]

After getting sidetracked I'm still back to my original thoughts. I am confident that the cap was off and frozen to the winch line for the week. I am also confident that the oil only started leaking out at the end of the trip because even though the hoses and the valve cover and intake manifold were covered, none of it had run down to the exhaust manifold yet so no smoke. I am also not worried about damage. I am mostly curious about why it took so long to start blowing out. I am wondering if i was taking in a lot of moisture with no cap and if the pcv could have become frozen and then built of pressure. Doesn't seem likely as it would have quite a bit of heat there from the engine but just grasping.

 

[JeepinPete]

Both times I have done this, I got the smell once I got on the highway. But the ride from my house to the highway is only a couple miles, so the oil certainly wasn't up to temp before I got on the highway either.

@SmokingRocks, You have got things backwards, and I would say it is you that needs to check his PCV valve. The PCV system does not pull a vacuum on the crankcase of an engine. Why is this? Because there is a filtered air supply into the crankcase of the engine, which happens to be right across from PCV valve on the 1FE. That hose happens to be close in size to the PCV valve hose. Perhaps it restricts air flow enough that idle isn't effected if the PCV valve goes bad. But with a working valve, it will make no difference if the oil cap is in place or not, at least as far as the idle is concerned. The PCV valve restricts the flow through the crankcase at low RPM situations.

Here is a cut and paste from agcoauto.com:

"At an idle, engine speed is low, around 600 RPM. A relatively small amount of fuel and air travel through the intake at idle speed. If the PCV valve did not regulate air flow, the engine would act like it had a vacuum leak. Too much air flowing into the intake causes the engine to lean out [too much air in relation to the fuel] and misfire. At an idle, the PCV valve restricts air flow, to reduce this problem. At high manifold vacuum [idle], a spring loaded valve is drawn up and partially restricts flow to the crankcase."

 

[SmokingRocks]

You’re all so right I know nothing about how a simple spring valve works when vacuum is applied. And yes I am sure my fully rebuilt engine and PCv valve with 25k on them are in much worse condition than your Hundo thousand mile unit.

Others corroborated my findings and I challenge you to replace your POV valve for 7 bucks and report back to me what happens when you have a properly functioning valve and you remove the oil cap.

I was being nice and even provided part numbers and pricing. Hopefully you both will be able to figure this basic concept out.

 

[SmokingRocks]

STRAIGHT from the the FSM.

I'm done being nice.

This isn't fxxxing rocket science, everyones advice has been pointing to the same thing. Now its up to you to fix it or ignore it and chase non-existant trolls out of your engine.

Replace your damn PCV valve or go to a mechanic for this s*** since you obviously aren't willing to take advice.

 

[SmokingRocks]

Both times I have done this, I got the smell once I got on the highway. But the ride from my house to the highway is only a couple miles, so the oil certainly wasn't up to temp before I got on the highway either.

@SmokingRocks, You have got things backwards, and I would say it is you that needs to check his PCV valve. The PCV system does not pull a vacuum on the crankcase of an engine. Why is this? Because there is a filtered air supply into the crankcase of the engine, which happens to be right across from PCV valve on the 1FE. That hose happens to be close in size to the PCV valve hose. Perhaps it restricts air flow enough that idle isn't effected if the PCV valve goes bad. But with a working valve, it will make no difference if the oil cap is in place or not, at least as far as the idle is concerned. The PCV valve restricts the flow through the crankcase at low RPM situations.

No, I don't have it backwards. Read the FSM. The PCV valves main job is not regulating flow, thats not what its there for. Its an emissions control device that sucks up hydro-carbons from the crank case and puts them in the intake manifold to go through the process of combustion.

TEST THE PCV as follows (But since both of yours obviously aren't flowing under vacuum condition they both need to be replaced) IIRC Toyota has them set as a 20k mile service item

 

[SmokingRocks]

So i guess its just a midwest kind of thing since you say you know everything there is to know about these truck. I realize i don't have your time or experience here on mud but i can read, and post after post are telling stories of their truck idling with no issues with oil cap off. As I'm from Missouri I have that "Show-me" mentality.

1. My truck runs with almost no change of idle with the dipstick out or cap off. It does die if i pull of the hose on the PCV valve.
2. The LX450 down the street is exactly the same. No issues with cap off or dipstick out. Dies if you pull the PCV hose

ANY mechanic would STOP HERE. You get a gold star because you found the problem, not only for your rig but apparently every 80 in a 150 mile radius.
You may choose to ignore my advice but don't ignore the Toyota Repair FSM advice...

Then again.... if you like to learn the really hard way I'll shut up "be wrong" and watch this thread grow as you search for unicorns in your 1fz.... good luck.

 

[Rifleman]

I'm amazed it run at all. With my cap off it borders on dying

My truck won't run at all with the oil cap off, if i try to remove the cap while the engines running, it creates such a big vacuum leak that it kills the motor right away.

 

[baldilocks]

Its funny the varying effect leaving the cap off has. On my '95, there is no change in idle or performance. Done it twice, made a mess both times, but other than the smell of the burning oil on the exhaust manifold, I had no other indication.

I’ve had three 80’s of the 93-94 models. Two would stall as soon as the oil fill cap was removed. The other one wasn’t bothered at all by removing the oil cap.

 

[gummycarbs]

I was curious, so after a drive around town to warm everything up, I tried it. The moment I unscrewed the oil cap, the engine idle dropped way down. It stumbled and almost died, then bounced around 375 - 425 RPM for several seconds. Over the course of 12 - 15 seconds, the idle recovered to a steady rate just over 600 RPM. I screwed the oil cap back on and the idle shot right up to 650, then settled down to its normal 625. (These RPMs are all estimations from watching the tach, as recorded on my phone)

This is on a '94 that has had all vacuum hoses replaced over the course of the last year. The EGR is still bypassed (need to rewrap the harness before restoring the EGR), including plugging the tube that goes to the bottom of the EGR modulator (a common cause of vacuum leaks, based on reading 'mud).

Having taken an 80 from running despite numerous vacuum leaks and observing the improvement as I fixed each one, it's my opinion that if you can unscrew your oil cap without affecting your idle, then you need to get to work fixing your other vacuum leaks.

 

[SmokingRocks]

It’s likely your IAC valve (idle air control valve) correcting to maintain the intake manifold vacuum

 

[REKCUT]

what is it/where’d you get it?

ANY mechanic would STOP HERE. You get a gold star because you found the problem, not only for your rig but apparently every 80 in a 150 mile radius.
You may choose to ignore my advice but don't ignore the Toyota Repair FSM advice.

What problem do you seem to think i have? I never said I had a problem. My truck runs perfect. I have no lights on. I have a new PCV valve. My thread was about how long you can go without a oil cap off.

I do see one discrepancy. All of the truck I have tested have been 95-97 trucks. IT seems from reading the bylines that everyone that is saying there truck dies when the cap is off is listing a 93-94. Don't know if this make a difference or not.

 

[SmokingRocks]

The engine will continue to run fine with a blocked pcv. That doesn’t mean it’s not functioning correctly. This is what is frustrating with your ‘diagnosis’ you claim that because the engine runs fine that there is t an issue with your valve.

There is one valve from Toyota for both the 93/4 and 95-97 1fz’s. It functions exactly the same way. A blocked valve will cause your engine oil to get contaminated much faster which could lead to sludge buildup. I know you’re thread was about how long you can go with the cap off but upon reading further information you provided it began to point to another issue which may have contributed to your oil cap popping off.

The oil cap test is an indicator and should be followed up by the test shown in the fsm. I suggest you follow the Toyota FSM.

I'm glad you are reaching out to other 80 owners to see if it happens to them but thats not how mechanics troubleshoot.