Update On The LeSabre

[Taylor Martin]

The mechanic made a house call to check out my grandmother's 2001 Buick LeSabre and we ran a few simple tests.

1.) Turned the car on
2.) Put the car in drive
3.) Drove around the block

What happened was rather odd.

We start the car and it's as if the car is constantly flooding. Like, it sputtered to a start almost every time, but eventually ignited. The first time we started it, a bit of gas did come out. So is an injector injecting too much post-shutoff? The world may never know.

Put the car in drive and suddenly the slightly abnormal idle turns to a complete misfire. The car's shaking with every crank, so clearly something is up.

But wait... it gets odder...

After a couple minutes (maybe less) of just letting the car idle in drive, the engine suddenly... worked... smooth as butter, just idled like normal. Drove it around the block and it's the same story.

Also, with the brake, I mentioned it was hard to press while driving. However, when the car was in park, it was fairly soft. So it was only hard while in drive/moving the car around.

I can't make heads or tails of it, but if it makes you feel good, the mechanic also suspected a vacuum leak. I think it's something in the engine, maybe an injector just got clogged/continues to get clogged and that causes misfires?

I'm no mechanic. I welcome your thoughts.

[CB]

@taylor-martin Ghosts.

[Chariotoflove]

@taylor-martin said in Update On The LeSabre:

The mechanic made a house call to check out my grandmother's 2001 Buick LeSabre...

I have no solutions for you. I just want to point out that this statement makes me happy.

[Highlander]

@taylor-martin said in Update On The LeSabre:

the mechanic also suspected a vacuum leak

Yes.

[Taylor Martin]

@chariotoflove said in Update On The LeSabre:

@taylor-martin said in Update On The LeSabre:

The mechanic made a house call to check out my grandmother's 2001 Buick LeSabre...

I have no solutions for you. I just want to point out that this statement makes me happy.

I'm glad

[Taylor Martin]

@cb said in Update On The LeSabre:

@taylor-martin Ghosts.

Spooky

[dogisbadob]

Had the car been sitting awhile?

@cb said in Update On The LeSabre:

@taylor-martin Ghosts.

It is that time of year, isn't it?

[Taylor Martin]

@dogisbadob said in Update On The LeSabre:

Had the car been sitting awhile?

Not very long, no. It was off for two weeks, then I drove it two days ago and it felt a little weird but fine. Then yesterday it started missing, and today it's smoothed out after a few minutes... huh?

[TheBarber]

@taylor-martin What does the exhaust look like on a cold start? What is the coolant level at?

Two things come to mind when misfires on cold start that clear out. Fuel flooding or coolant flooding.

Injectors can leak down when the engine is off causing a misfire on cold start due to excessive rich condition that eventually clears out enough to not cause an obvious misfire.

IIRC these motors had an problem of coolant leaking into the intake manifold. This can also cause a cold start misfire that will clear out.

The change in abnormal idle to complete misfire is just a misfire under load. The engine is already struggling to run and then you put a load on it in drive.

It really needs to be determined whether it is a single cylinder misfire or a multiple cylinder misfire.

The brakes sounds like a seized caliper or caliper pin.

[Taylor Martin]

@thebarber said in Update On The LeSabre:

IIRC these motors had an problem of coolant leaking into the intake manifold

Oh... that sounds expensive. And the coolant does "hiss" after you shut off the car even when it's not really hot.

Coolant flooding would suck.

[TheBarber]

@taylor-martin Depending if that is the issue, which I am not saying it is... yes it could be expensive. Coolant flooding sucks, coolant hydrolock is fatal. Either way you don't want to keep having the car running like it is unless you want costs to compound.

Kinda hard to diagnose from behind a keyboard. But I would say the car should be taken in and given a good look over and properly diagnosed.

[Shop-Teacher]

@taylor-martin I suspect this car has more than one problem, but a vacuum leak is almost certainly one of them.

[AdverseMartyr]

@taylor-martin Well, I would venture random guesses if this was a 70-80s 480SL, and used that injection system. Considering I eventually just let a mechanic fix it anyway though... sounds like you are on the right track already

[MM54]

@taylor-martin Vacuum leak or sticky injector, either way it's throwing off the cold-start mapping but when it gets warmed up and into closed loop control it's able to compensate.

[RallyWrench]

@taylor-martin Odd combination of symptoms. Every internet diagnostic will inevitably say "vacuum leak," but hear me out...

With the change in brake assist and engine symptom, I wonder if the brake booster diaphragm is failing. When you hold the brakes or accelerate, it depletes the vacuum which would otherwise be held in the system. Allowed to idle long enough, it'll pull enough vacuum to build assist again and maybe reach equilibrium with the calculated airflow. The dead misfire is a little weird here, but the abnormal idle would be easily explained by an air leak like this. If the vacuum leak is big enough it could cause a miss, but I think in that case it'd be audible. I don't have enough experience with these to know if boosters are known to go, but it's certainly old enough, and I see it often enough on various VWs for it to come to mind.

[TheBarber]

@rallywrench
Good line of thought!

A quick test would be to pinch off the vacuum line to the booster.

I actually had one of these once on a CRV. In my case it wouldn't misfire, the engine would just go pretty lean anytime you hit the brake pedal.

Although if the abnormal idle is clearing on it's own that wouldn't make sense. I guess duration is the key to that? Still, a leak of that magnitude would probably set a lean code especially while driving. Alas, once again, knowing single or multiple misfire would be the first step on what path to take.

[Taylor Martin]

@rallywrench said in Update On The LeSabre:

With the change in brake assist and engine symptom, I wonder if the brake booster diaphragm is failing.

Ooh, that's interesting. The brakes felt just fine in park, and in drive while holding still, but stiffened after I set off again. In other words, your theory checks out (minus the misfire, which I think is an injector or a vacuum leak... or both).

Regardless, now all I need to do is figure out what a brake booster diaphragm is, and where the hell it is.

[speedy964]

@taylor-martin Here is a video on how a vacuum assisted brake booster works