318 hunting on acceleration

My friends 1997 318i coupe seems to be suffering badly on acceleration in first gear only. It hunts severely unless the clutch is slipped, it seems to step up the revs in 1000rpm steps as if you are jumping on and
off the accelerator at those points.
Other gears power seems to be normal, but I'm not sure how powerful this should be.
It hasn't been all that well looked after, still has same spark plugs in from when he bought it, but he would change them if he thought it would help.
Feels more like an engine problem rather than clutch or drive related, just too severe and on/off.
Any clues?
-- Tony
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How many miles does it have on it since he bought it? Does it have the same fuel filter, air filter, and oil?
If it were me, I'd first do all the preventative maintenance on the schedule that has been missed, then I'd do a general look over for vacuum leaks, then I'd pull the codes off the computer and see what it's saying. All kinds of things can cause this sort of behaviour, including believe it or not, the oxygen sensor. But vacuum leaks are high on the list. --scott
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"C'est un Nagra. C'est suisse, et tres, tres precis."

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I agree with Scott, good chance it's a vacuum leak. Most likely one is a ripped hose from the throttle body to the air flow sensor (the biggest hose in the enge bay), you'll likely need to flex it to reveal the rip.
If the car has no history you really need to fit new spark plugs and change ALL the fluids and filters.

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Email: snipped-for-privacy@unixnerd.demon.co.uk, John G.Burns B.Eng, Bonny Scotland
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John Burns wrote:

We did a basic service for oil, oil filter, air filter recently but spark plugs no and fuel filter no. I agree these should be done anyway, but I just thought that as all other gears accelerate normally it wasn't a fuel/spark problem, but you never can be sure.
I don't know the milage, probably around 90Kmiles. He's kind of running the car into the ground, but is prepared to do whatever is needed. I know this is not a good attitude but he doesn't have alot of money, and isn't really into cars. I try to explain that a newer car will be more expensive than good maintenance but most people just don't get this.
I will have a look at the vacuum hose the next time I see it. Thanks for the help, I'll post an update if anything to report.
-- Tony
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Tony wrote:

The owner says he can see cracks in a inlet rubber duct, seems to be the likely cause. Thanks for the suggestions, they really helped.
-- Tony
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