Our Community is 940,000 Strong. Join Us.


96 Lumina Rough Idle, no brakes


jeranamo
11-06-2007, 10:36 PM
My girlfriend's 1996 Lumina LS has been working fine since we got it a few thousand miles ago (it's at about 122,000 right now). When she went to start it tonight after work it idled very rough and wouldn't stay started. She told me she attempted to reverse out of a parking space and the brakes were very hard to press. I met her at work and tried starting the car and giving it gas to increase RPMs for a while. I thought it may have been a clog in the fuel lines or filter possibly. Maybe it still is a possibility. Even at the proper "warmed up" temp for the car, it still idled rough and you have to literally STOMP the brake pedal in order to get ANY braking at all (i tried test driving the car around the parking lot). Also, I should note: the check engine light was NOT on for the longest time. Then near the end I shut off the car for a minute, turned it back on and the check engine light came on. We left it in the parking lot and I drove home. I will go back again tomorrow afternoon and try a few things before calling a tow truck I guess.

Anyway, I'm stumped on what to do and I'm not necessarily looking for a way to fix this right now on my own, but I'd like some insight as to what this problem could possibly be and/or if anyone else has experienced the same or similar situation.

Thanks,
Ryan

jeffcoslacker
11-06-2007, 11:21 PM
Sounds like it blew the vacuum line for the brake booster off...just follow the hose from the booster and see what happened...

jeranamo
11-07-2007, 08:47 AM
Is the brake booster right next to the reservoir?

Also, do you think the engine acting how I described above could be due to dead spark plug(s)? If there isn't any ignition in a certain cylinder, causing it to misfire, would that cause the engine to run so rough that it won't stay on without giving it any gas? The engine shakes in the same fashion as if it's turning over when the RPMs get to the "idle" range.

Her dad said it could be a bad PCM, is there an easy way to bypass the PCM just to see if the engine will run better?

jeffcoslacker
11-07-2007, 10:28 AM
A vacuum line off presents a majorly over-lean condition...lean mixture causes misfiring...with something as large as a vacuum booster supply hose off, it will struggle to idle, and probably die. The injection system can only overcome so much extra air bypassing the throttle plate.

It's not uncommon for these motors to "sneeze" back through the intake when shut down or if short-cranked accidentally and blow a vacuum line off...especially once they get older and the hoses don't fit as good...

The only way to explain the sudden behavior and the lack of power brake boost is catastrophic vacuum leak. I wish you'd just check it before going all mental on it....

Do I understand it runs ok at part throttle in park? It will overcome the vacuum leak when the throttle is opened...if you can't spot the leak try plugging the vacuum line to the booster at the engine and see what happens

If you have no brake assist even with the engine revved I'm positive this is what happened.

Your ECM is not the problem, and no, the car will not run without it.

jeranamo
11-07-2007, 02:14 PM
You were correct. The vacuum line from the brake booster blew off. I wasn't being "mental" though. I replied to your post from my home and the car was in a parking lot about 10 miles away and it was pitch black. I wasn't about to drive home with no brakes.

Anyway, I thank you for your help because that's what the problem was. I slipped the line back on the booster and the car started right up. It had the check engine light on due to it being triggered as multiple misfire (I took the car into autozone after I got it running to have it scanned and reset.) but it is obvious it isn't misfiring now. I picked up a hose clamp from autozone to keep the hose on the booster for good. (btw, do these cars even have a clamp over the booster when they came from the manufacturing plant? Just wondering why there wasn't one there to begin with).

Once again thanks for you help, jeff.

jeffcoslacker
11-08-2007, 05:24 AM
I just didn't want you overthinking it...I was pretty sure that was the issue.

Lotta times they don't clamp vacuum lines, since they are under suction rather than pressure, they don't tend to come off...but when they get older and fit a bit looser, the occaisional intake backfire can sneeze them off...I'd take a look at the others and make sure there's no more on the verge of popping off too...

Gotta love a cheap fix, huh? :iceslolan Glad that was the problem.

Add your comment to this topic!