1999 Pontiac Bonneville Bonneville in need of help!

MGMYERS

MEMBER
1999 PONTIAC BONNEVILLE
6 CYL
2WD
AUTOMATIC
231,000 MILES

I was coming home yesterday, down a series of hills, and my car quit out of nowhere. I coasted through several stop signs (got lucky) and tried to start it up again. The car would start but die without pumping the gas pedal. Upon putting it in gear, the car dies no matter how much gas is given.

Managed to get it home despite a large hill to get here, and did some experimentation. It would still start but idle was choppy. Putting it in gear up and down the driveway caused no problem but choppiness. Now I have it idling fine at 1k rpm. After revving it to 3k, the idle gets choppy, then self-revs to 2k, then returns to normal 1k rpm.

Update: After ten or so minutes, a slight rev makes the engine play with the idle, it goes up and down, to 2k then almost stalling, settling at 1k and then moving up and down again.

The check engine light is on, and the battery appears to be working with less charge than before the problem started. Also the heater core was leaking, so I cut and reconnected that hose. What came out was a viscousy red gunk.

5 Replies

MIKE H R

MECHANIC
3,094 POSTS

I would first start with the fuel filter, sounds like the fuel filter is getting clogged up. I suggest that after that, the cooling system be looked at, it should be flushed and the thermastat relaced. If there is that much gunk in the coolant the thermastat ciould give you problems if not changed. The fluciation in rpms is from a little gas getting through the filter to barely keep the car running, just like you were out of gas.

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Sunday, June 14th, 2009 AT 8:19 PM

MGMYERS

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3 POSTS

I could see the fuel filter being at fault for much of this, but.
I can still rev the engine with no problem. In fact, it sounds better the more gas I give it. Same goes for when it is in gear. The problem, stalling out or fluctuating idle, happens when I stop supplying gas.

Could the fuel filter still be at fault?

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Sunday, June 14th, 2009 AT 10:15 PM

MIKE H R

MECHANIC
3,094 POSTS

With the car ideling in gear or out, the fuel demand is less since its not moving the car. The more load you put on the engine the more fuel you use. Being a 1999 with over 231,000 mniles on it. Get some throttle or carb cleaner and clean out the throttle body, sometimes over time air holes can get clogged with carbon, Had to do it on my subaru a couple of times. Follow instructions on the can. See if that helps with the idle.

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Thursday, June 18th, 2009 AT 7:06 AM

MGMYERS

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3 POSTS

Got a chance to run the scanner code, and it said the mass air flow sensor was suspect. We took that out and sprayed some cleaner on it, which returned the car to normal for a short while. We'll be changing the MAFS, but I have one more question.

Is there another problem that could cause the MAFS to malfunction? Should I be changing anything else out at the same time?
Thanks so much for all your input!

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Thursday, June 18th, 2009 AT 12:26 PM

MIKE H R