Same f*cking problem

[McLin]

Hi,

we have every year the same problem, today my gf is driving and parks the car and let her child out with running engine.
After she does it she press the brake pedal and put into reverse and the brake pedal is very hard and the car is shaking, like stutter.
The upper Intake Manifold is replaced, the brakes are new, the Air filter is new, the fuel filter is new, spark plugs are new, wires are new, ignition module is replaced from another Lumina, fresh oil and cooling water.

I still desperate, please help me. Oh and no trouble codes...

98 LTS 3.8L V6...

[McLin]

The Lumina did this failure once or twice a year.

[jeffcoslacker]

You know, ever since it was new, my '97 has once in a great while, especially in cold weather, had a rock hard brake pedal and misfire...

I always suspected the booster had a relief inside getting iced or something, but of course I could never get it to do it at the dealer, so it was considered unfounded problem, no warranty fix.

I've watched TSB and recall info for similar problems, but never found anything useful.

Anyway, like I said, I suspect a ball check or something in the booster gets stuck, and opens the vacuum side of the diaphragms to atmosphere or something...creating a huge manifold vacuum leak and no power assist...

[j cAT]

Originally Posted by McLin

The Lumina did this failure once or twice a year.

a hard pedal is usually the booster as the total cause...

however it can be vacuum lines feeding the booster.

I would hook up a vacuum line to the intake manifold at idle it should be 15-21 inches. have GF push down on brake pedal. if the vacuum drops the booster is NG...also make sure the hose to from booster is good and the ends securely attached.

[McLin]

It happened again, I replaced all parts on same time this summer which I replaced with new LIM gasket.

Its hearing like one cylinder is not running and smells like Firecrackers.

I checked the vacuums line and spray it so no leak is there. After 30 min. I drove home and no symptoms anymore.

[jeffcoslacker]

Did you replace the booster's vacuum check valve yet?

Mine does the hard pedal and misfire occasionally, usually in cold weather, right after start-up. But just for one or two pedal applications, then it's gone. This keeps happening for a while to yours I guess? I'd replace the booster check valve, vac hose, make sure the grommet in the booster is in good shape, etc.

When we first got the car it would "lope" and misfire slightly sometimes if you barely pressed the brake pedal while stopped...push it harder and it would stop doing it. I've heard other Lumina owners have similar issues. I think there was some problem with these boosters, but I've never seen anything official about it. It seemed to grow out of that problem after the first year. But it continues to suck air every now and then...

[gmtech1]

If the vacuum lines are ok, check valve ok and seal at the valve ok, I'd be looking at the booster.

[Schurkey]

Originally Posted by jeffcoslacker

Mine does the hard pedal and misfire occasionally, usually in cold weather, right after start-up. But just for one or two pedal applications, then it's gone.

Also. Somewhat disappointing as this is one of the "rebuilt" boosters I installed about three years ago when I did both Luminas. OTOH, it's so rare I can't work up the gumption to rip it back off and hand it over for warranty replacement.

Failed--or partially-failed--boosters seem to be a major problem on (at least) the first-gen W body.

The vacuum hose from the rear side of the upper intake manifold to booster was quite rotted on one of my 3.4 Luminas; I noticed it when I replaced the booster. Common part; seems to be the same as used on the 3.1. If perforated, there'll be a vacuum leak that might vary depending on engine shake (engine pulling on the hose)

[Tech II]

Never ran into a booster problem......but have run into the check valve being the problem......

[McLin]

Thank you all, did I have to remove the cylinder head to check the valves?

[Schurkey]

Originally Posted by McLin

Thank you all, did I have to remove the cylinder head to check the valves?

No. You're being asked to inspect the plastic check valve pressed into a rubber grommet in the brake booster that the vacuum hose to the booster attaches to.

That little check valve, or an internal booster problem, seem to be the most likely cause of your engine running poorly.

[jeffcoslacker]

http://auto.howstuffworks.com/auto-p...wer-brake1.htm