325iX starts but won't stay lit.

It's a high mileage '91 325iX, and suddenly today, at cold, it cranks, fires and starts fine but the engine won't stay lit unless I continually goose the throttle. It's not engine speed related, I can
goose it up to 2,000 rpm but when I try to hold it there, it dies, like it's not getting fuel.
Bentley says that a vacuum leak has to be huge for Motronic 1.1 not to be able to adapt to it. All the vacuum hoses appear to be connected and intact, so I'm guessing that's not it.
Bentley says test the fuel pump next. Maybe, but the engine will run smoothly so long as I keep goosing the throttle. Doesn't *seem* like the fuel pump's bad, does it? Maybe it's not seeing the engine speed signal and I'm somehow compensating for that with the throttle activity?
Bentley says that Motronic 1.1 cold starting is entirely managed by the ECU, so there's nothing mechanical to check in the cold start system. It seems like something isn't seeing and/or reacting to an engine idle signal or condition, though.
No fault codes are present.
Any suggestions for what to check next? I'm an M20 newbie, so be gentle with me.
--
Dan.

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It does sound like one. But I'd also check the rotor arm isn't fractured.
I had this on my 635, it WAS a vacuum leak. But it was hard to find.
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I would say check your fuel system for proper operating pressure, also check injectors for proper flow. My friend had a problem like this on his 94 E36 325i and it turned out to be a faulty Mass airflow sensor. You also might want to disassemble and inspect your intake manifold / throttle body.

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On 29 Jan 2007 06:53:46 -0800, snipped-for-privacy@hotmail.com wrote:
Thanks, both, for the suggestions. Being a working stiff and given the time of year it's going to be next weekend before I get around to doing any more with this.
I'll post the answer once I figure out what it is.
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Dean Dark wrote:

Most likely the fuel pump is dying on you, or you have a clogged fuel filter. Check filter first, then the pump.
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Well, this past weekend I dismantled pretty much the whole intake side without finding any vacuum leaks. I don't doubt that the fuel feed is the next logical thing to check but I'm puzzled as to why goosing the throttle keeps it running fine. There's no rush, I'll do it and write up whatever the answer turns out to be.
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I still think fuel pump or FILTER... have u replaced the filter recently?
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On Mon, 5 Feb 2007 20:21:21 -0500, "SharkmanBMW" <sharkmanbmw at gmail dot com> wrote:

Yes, filter first is the plan. I have no idea when or if it has ever been replaced.
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I finally got around to it again today, and replaced the fuel filter. Problem solved. And this past week here in the NE US, I could really have made good use of the car...
Thanks for the suggestions.
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My mechanic always changes the fuel filter first when any issues arise... it solves most idle or running probs. I have an xi also... been fun this last week!
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On Sat, 17 Feb 2007 12:51:12 -0500, Dean Dark

Well, I spoke too soon.
Today, the problem suddenly came back while I was on the road. I could barely keep the engine alight enough to keep the car going. I had to pull over on the shoulder, and then I turned the engine off. Straight away, I started it again and it ran like a champ and I zipped the remaining 10 miles or so home like a bastard. I guess the fuel pump is next on the list, unless anyone has any other ideas...
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Fuel Pressure Regulator would be high on my list of suspects. Especially if it seems to run ok for a while after being restarted. Have a look at your catalytic converter after the next time you've kept it running by goosing it for a while. Cherry Red means too much fuel = fuel pressure regulator.
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wrote:

Thanks for the suggestion. I appreciate it.
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