’88 735il rough idle;some hesitation

I have a rough idle, and some hesitation on accleration. Im new to a
BMW, so i cant quite nail it down. Did a complete tune-up, the works,
but no difference. I was reading up on my model, but they dont have
many specs for it. I go to the auto parts store and they can only pull
up the 3.4L, not the 3.5L that my car has. Could this be the problem?
I got pregapped plugs, but at the time I didnt know there was the two
different engine sizes. Or could it be something else? Where can i get
the right parts for it?

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"deznutts" > wrote
>I have a rough idle, and some hesitation on accleration. Im new to a
> BMW, so i cant quite nail it down. Did a complete tune-up, the works,
> but no difference. I was reading up on my model, but they dont have
> many specs for it. I go to the auto parts store and they can only pull
> up the 3.4L, not the 3.5L that my car has. Could this be the problem?
> I got pregapped plugs, but at the time I didnt know there was the two
> different engine sizes. Or could it be something else? Where can i get
> the right parts for it?

Although it was labeled 3.5L, it's only 3430cc, which actually makes it
a 3.4L after rounding.

Almost always, on the M30 engine, a rough idle means that you have
a vacuum leak somewhere in the system. Make sure that the oil
level stick is in all the way. Very carefully check all *all* *ALL*
the rubber on the intake side for cracks. You often have to use
a smoke source (candle) to find leaks. Check all hoses and lines
to make sure they're connected.

FloydR

"Floyd Rogers" > wrote in message
acquisition...
> "deznutts" > wrote
>>I have a rough idle, and some hesitation on accleration. Im new to a
>> BMW, so i cant quite nail it down. Did a complete tune-up, the works,
>> but no difference. I was reading up on my model, but they dont have
>> many specs for it. I go to the auto parts store and they can only pull
>> up the 3.4L, not the 3.5L that my car has. Could this be the problem?
>> I got pregapped plugs, but at the time I didnt know there was the two
>> different engine sizes. Or could it be something else? Where can i get
>> the right parts for it?
>
> Although it was labeled 3.5L, it's only 3430cc, which actually makes it
> a 3.4L after rounding.
>
> Almost always, on the M30 engine, a rough idle means that you have
> a vacuum leak somewhere in the system. Make sure that the oil
> level stick is in all the way.

And the oil filler cap is screwed up tight - I had this once!

> Very carefully check all *all* *ALL*
> the rubber on the intake side for cracks. You often have to use
> a smoke source (candle) to find leaks. Check all hoses and lines
> to make sure they're connected.
>
> FloydR
>

"R. Mark Clayton" > wrote in message
...
>
> "Floyd Rogers" > wrote in message
> acquisition...
> > "deznutts" > wrote
> >>I have a rough idle, and some hesitation on accleration. Im new to a
> >> BMW, so i cant quite nail it down. Did a complete tune-up, the works,
> >> but no difference. I was reading up on my model, but they dont have
> >> many specs for it. I go to the auto parts store and they can only pull
> >> up the 3.4L, not the 3.5L that my car has. Could this be the problem?
> >> I got pregapped plugs, but at the time I didnt know there was the two
> >> different engine sizes. Or could it be something else? Where can i get
> >> the right parts for it?
> >
> > Although it was labeled 3.5L, it's only 3430cc, which actually makes it
> > a 3.4L after rounding.
> >
> > Almost always, on the M30 engine, a rough idle means that you have
> > a vacuum leak somewhere in the system. Make sure that the oil
> > level stick is in all the way.
>
> And the oil filler cap is screwed up tight - I had this once!
>
> > Very carefully check all *all* *ALL*
> > the rubber on the intake side for cracks. You often have to use
> > a smoke source (candle) to find leaks. Check all hoses and lines
> > to make sure they're connected.
> >
> > FloydR
> >

I have the same car with 145k miles. A few months ago, it starts fine but
runs rough for a minute then goes okay. It occurs about once a week. It is
due for service but I don't know what it is. Here in Florida we stock up on
gas for the generator for hurricanes. Each summer, we take the year old gas
and toss it in the lawn mower and in the 4 cars we have. It's been okay. The
camper had trouble starting after putting too much in, so we stopped doing
it. I had put a gallon or two in the BMW but the problem was happening
before that. So check for old gas (I know, not likely). I don't know
anything about cars so the others can help. Good luck.

"boat987" > wrote in message
ng.com...
>
> "R. Mark Clayton" > wrote in message
> ...
>>
>> "Floyd Rogers" > wrote in message
>> acquisition...

> Here in Florida we stock up on
> gas for the generator for hurricanes. Each summer, we take the year old
> gas
> and toss it in the lawn mower and in the 4 cars we have. It's been okay.
> The
> camper had trouble starting after putting too much in, so we stopped doing
> it. I had put a gallon or two in the BMW but the problem was happening
> before that. So check for old gas (I know, not likely). I don't know
> anything about cars so the others can help. Good luck.
>
>

Water in the gas or just evaporation of the higher fractions if your storage
tank is not a hermetic seal?

I have a '89 735 auto and have a 'hicup' if I try to pull away quickly and
sometimes a 'miss' when cruising. I spoke to a mechanic (not BMW) who said
there could be a faulty connection somewhere and suggested a diagnostic by a
BMW garage. Diagnostics can be expensive so for the time being I have left it.
Lumpy running on tickover can be a faulty air sensor. This can be checked on
the diagnostic and if it is a nuisance is worth paying to have it checked.
Not much help I'm afraid but just to let you know you're not alone with
annoying problems.

"deznutts" > wrote in message
news:1207247_0708de71d756034665d891dec1eee4ff@auto boardz.com...
>I have a rough idle, and some hesitation on accleration. Im new to a
> BMW, so i cant quite nail it down. Did a complete tune-up, the works,
> but no difference. I was reading up on my model, but they dont have
> many specs for it. I go to the auto parts store and they can only pull
> up the 3.4L, not the 3.5L that my car has. Could this be the problem?
> I got pregapped plugs, but at the time I didnt know there was the two
> different engine sizes. Or could it be something else? Where can i get
> the right parts for it?
Bad mass air....
>
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> interface
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