Ugh... 92 Explorer Hell..

[natenkiki2004]

They're both systems that control the fuel & air mixture for the engine.

I will say though, unplugging the FPR vacuum line while running shouldn't affect the engine a ton. It'll just mean that the injectors will see higher fuel pressure than normal and you might get slightly more fuel at idle because of it.

You have an imbalance somewhere in the air/fuel ratio. Have you cleaned the MAF? Does unplugging either the ECT or IAT sensor make a difference how long it runs?

At this point, we don't know if it's a computer or mechanical issue, that's what makes it difficult to track down.

 

[MistahYebba]

I have cleaned the MAF recently, yes.

I have unplugged and capped each at a time the 3 that are the standard vacuum line size.

There are 3 on there however that are bigger than the standard size. I don't know the names of those ones.

I have a feeling that it's not electrical though, because remember, earlier when I was fooling around touching all the vacuum lines and stuff... I did get the truck to work with the IAC Valve plugged in. I was turning on/off the AC, hit the brakes, turning the wheel, putting it in to gear, etc.. everything was working at what I would call "great"..

I didn't really do much though..

So that makes me want to say it's not electrical and it's something that can be easily knocked in/out of place to work?

I must have gotten it working by accident and when I wrapped up and walked away, whatever I did went back into position to not work again?

 

[MistahYebba]

I can try to unplug those 2 sensors one at a time tomorrow but right now it's far too late. I'd post an update of course.

 

[MistahYebba]

I know I've been saying it's turning off the AC all this time that contributes greatly to stalling..

but one thing I've noticed is that, really, it's anything that adds extra load to the engine..

For example, if I'm at a stop light and I'm getting massively fluctuating RPM's as if my truck is trying to save itself from stalling--and then I turn on my headlights--the RPMs drop even more...

Or my hazards, or my wipers, or my ANYTHING that uses power.

This would point to the alternator at first glance, but I believe it's only because the alternator calls for power from the engine, and then when the engine calls for power, "insert here" goes wrong and I stall.

Still pointing to vacuum leak?

 

[MistahYebba]

In theory, is it possible to unplug and cap EVERY vacuum port at the same time on the vacuum tree and the car will still run?

In other words, is there any vacuum line that the engine is absolutely dependent on having in order to stay running?

I would imagine so, but which one is this?

 

[MistahYebba]

One more thing, does anyone have the name of the black plastic 3-way connector valve that has a discus shape with a stem on the left, a stem on the right, and a stem on the bottom?

 

[natenkiki2004]

Yes, you should be fine removing all the vacuum items. You technically need the fuel pressure regulator but it should still run without it.

As for turning lights on/off affecting RPM, it could be you have a bad ground for the computer. Check the battery cables, see if there's any corrosion or bulging near the ends. It may be alternator related too. RPM should never change no matter how much electrical load is on the system. You should be able to draw more amps than your alternator can provide and still run the engine, it'll just die when the battery is depleted.

 

[MistahYebba]

Well I know someone said that how hitting the brakes assists in causing it to stall could point to a brake booster vacuum leak?

But I almost want to say it's the fact that power brakes use power consumption as well...

and then I'd even venture to say that plugging in the IAC Valve electronics takes up power consumption too??

Just as turning on/off the AC is power consumption; turning the wheel is power consumption; basically everything is power consumption..

But once again, don't forget that I got it temporarily working yesterday.. That almost nullifies the possibility of anything being "broken"... and more or less something being disconnected I would imagine? "Hanging on by a thread" per se...

My idle is pretty bad. I mentioned how if I'm in gear at a stop light, it'll "VROOM VROOM, nearly die, quick save itself, VROOM VROOM, repeat".. as the battery voltage meter follows the sound of the revving.. dropping to very low, then going up to normal again.

Well, if I switch it into neutral it kinda stops that.

 

[Number4]

Is your brake fluid down?

 

[MistahYebba]

Not at all low on brake fluid. That would be too easy of a fix

If I turn my engine on with the IAC Valve unplugged, and then plug it in while the engine is running, it stalls literally INSTANTLY once the IAC Valve is plugged in.

I can't figure out how I managed to get it running yesterday with the IAC Valve plugged in... I hate that I temporarily fixed it and don't know how. :/

 

[natenkiki2004]

On Chevrolets, it's common for a heavy stroke of the brake to affect idle briefly. Think of it, the brake boost is full of vacuum generated by the engine. You dump that vacuum and it has to 'refill', it makes sense that it will affect the idle briefly and slightly. However, if it causes the engine to die or come close, that's not normal and it could be a leaking brake booster.

 

[Number4]

So your brake fluid isn't leaking into the booster, but you may still have a booster issue.

I don't recall, did you line this one off your list? Remove the line to the booster and plug it?

 

[MistahYebba]

But just note Natenkiki that the brake is only one teeny contributor to the possibility of stalling.

I've been driving around since yesterday and have only stalled a handful of times.

It's only when either coming to a stop, or at a stop completely.

I can cause it to stall whenever I want by turning off the AC and turning on my headlights at the same time while stopped and in gear.

I can also cause it to stall by plugging in the IAC Valve while the engine is running.

I can stop it from "HIGH REV, nearly stall, HIGH REV, nearly stall" when at idle by kicking it into neutral... which is a fix that lasts for like 10 seconds.

and most importantly, I got everything in working condition yesterday for like 10 minutes by messing around with vacuum lines and stuff... until I wrapped everything up and walked away.

That bit of information must narrow down the list of possible culprits greatly, shouldn't it??

 

[MistahYebba]

I don't know which one the brake booster is.

There is 3 smaller, standard size vacuum lines, and 3 then big vacuum "hoses" that are larger than any caps I have, so I did not attempt to cap off any of the 3 bigger ones. I will have to swing by the autoparts store and by a variety pack of caps to try that.

Which one on the tree is the default brake booster "nipple"?

I think maybe we are focusing too much on the "brake" aspect of this all and forgetting the fact that when I plug in my IAC Valve while the car is running, my engine stalls right away as soon as it's plugged in.. and with it unplugged, the car runs -- albeit very roughly.

That can only be a few things, right?

 

[MistahYebba]

Oh and then of course the 7th "nipple" on the vacuum tree which is capped off by default.

 

[MistahYebba]

and by "rough running" with the IAC Valve UNPLUGGED..

I mean, when I take off from a stop for example, it hesitates big time. It makes my whole body rock back and forth like 3 times before it steadies out.

And at a stop, of course I've already said how rough the idle is.

 

[MistahYebba]

You may say..

"Hey, if the car works with the IAC Valve unplugged, and it instantly stalls after starting with the IAC Valve plugged in... just leave that crap unplugged!"

Well... that's how I've been getting to and from work!

But I want it plugged in!!!! I'm sure you can imagine why.

 

[natenkiki2004]

All we know is that there's a fuel/air mixture issue. Where, that's the big question.

The brake booster is the big black canister under the fluid reservoir. The big vacuum line coming off of it is the biggest one by far on the tree.

When you're stopped in gear and idling and can make the engine die, try taking your foot off the brake and then try to get it to die. This all could be related to the brake boost. Like I said, I had many vacuum leaks on my Ex when I got it. 4 holes in various plastic lines and a severely leaking brake boost grommet. Even with that and a faulty IAT sensor, the engine never wanted to stall out or die. This makes me think that yours is a HUGE fuel/air problem that the engine computer cannot compensate for.


On a side note, you shouldn't be driving the vehicle like this. First off, it's a safety hazard. If the engine dies and you need to brake/steer/accelerate out of the way of a hazard, you're boned. Second, if it's a rich condition, you could destroy your catalytic converters. If it's a lean condition, you can cause internal engine problems.

 

[MistahYebba]

I went ahead and unplugged EVERY vacuum hose/line at the vacuum tree and capped every one of them off at the SAME time.

What result should I have expected?

 

[MistahYebba]

As shown in this video, every port on the vacuum tree is plugged/capped.




The truck was running...... I guess okay, maybe, possibly.

As you can see, once I connect the IAC Valve? Stall.

Same as when all the vacuum lines are connected.

So doesn't that rule out a vacuum leak?