Hesitation and boging down

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scarland
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Hesitation and boging down

Post by scarland »

Help I have a 1988 Hi line BMW 635 December make . At rest the engine idles beautifully and smooth on driving it starts to hesitate and restricted to 40km it then coughs .As soon as I put it in neutral it idles beautifully .
I have replaced fuel pumps, plug leads, rotor button and cap, put in new crank angle sensor, had airflow meter checked and repaired, had computer out and sent away for checking, said all was okay , a new o2 sensor and a new Mrp sensor,
still does it can anyone advise, I have just purchased a new engine temperature sensor also.

Can one use the stomp technique to get the fault to show on the engine light

Help any ideas. Scarland
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sharkfan
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Re: Hesitation and boging down

Post by sharkfan »

Have you checked fuel pressure under load? The symptoms you're describing exactly matched mine which was traced to a dirty fuel pick inside the fuel tank.
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scarland
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Re: Hesitation and boging down

Post by scarland »

Hi Sharkfan

Thanks for that I did replace the two pumps but did not think about pick up will get it checked. Scarland
scarland
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Re: Hesitation and boging down

Post by scarland »

Hi Dean Has anyone used smoking to test for vacuum leaks or leaks in the boot after the airflow control ?? scarland
scarland
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Re: Hesitation and boging down

Post by scarland »

Hi also have noted that the engine light does not come on when switching on ignition does this indicate anything serious or just a bulb gone all other lights come on ?? any ideas Scarland
Pod
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Re: Hesitation and boging down

Post by Pod »

scarland wrote:Hi also have noted that the engine light does not come on when switching on ignition does this indicate anything serious or just a bulb gone all other lights come on ?? any ideas Scarland
Change the bulb and then you'll know!
wattsmonkey
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Re: Hesitation and boging down

Post by wattsmonkey »

Is this a US thing? What engine light?
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hornhospital
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Re: Hesitation and boging down

Post by hornhospital »

The CEL (check engine light). All the warning lights are supposed to come on for a few seconds when you start it up, just as a check to show they're working. A CEL that doesn't illuminate when the key turns is a fail in most states that have inspections (M.O.T. in your case).
Ken Kanne
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miklilmag
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Re: Hesitation and boging down

Post by miklilmag »

Hello,
after extensive parts replacement like you did on a '88 this might be for you:
On my 90 735 they say you should disconnect both leads on battery ( negative/positive) and touch them together, best to remove battery!
After battery gone and they together, turn ignition to on position and wait two/ three min.\. Supposed to reset it,
shogun trick
good luck
scarland
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Re: Hesitation and boging down

Post by scarland »

Hi Miklilmag

Thanks for that . Not being a electronic man what that that do to the engine and circuitry,it wont damage anything will it ??
where does that Idea come from ???

What does it reset

I suppose its like closing down your computer and re booting it is that right ??

Qwilkin
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miklilmag
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Re: Hesitation and boging down

Post by miklilmag »

Hello, yes, reset to factory,
the only way to make sure not to damage anything is to remove the power source,
The idea came from bimmerforum.com, e32 section,


Good luck
scarland
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Re: Hesitation and boging down

Post by scarland »

Hi MIklilman

Many thanks for that by the way I have been offered a 90 735i for engine parts if i need them are thy similar to a 635 ??

Scarland
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miklilmag
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Re: Hesitation and boging down

Post by miklilmag »

Hello
Always good to have parts,
and yes, both m30's,
you can check on
http://bmwfans.info/parts-catalog/E24
for fitment
scarland
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Re: Hesitation and boging down

Post by scarland »

Thanks Millilmag

I search and yes lots of parts will accept his suggestion and raid it for parts

Scarland
scarland
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Re: Hesitation and boging down

Post by scarland »

Hi Miklilmag

Well down to just a hesitation now, took it our yesterday from cold had the hesitation but as it got warmer it seemed to clear then only every now and again hesitated .Created it also by holding foot on brake then accelerating so under load and it happened so back to it again.

thanks for all your help

Scarland
scarland
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Re: Hesitation and boging down

Post by scarland »

Hi Miklilmag

Just smoked it and zero leaks hurrah , but found the new Crank angle sensor put on is one which does not have a solid bracket on it can shake so buying a new one with a solid bracket on. It seems there are many on the market to match but there is only one with a solid tube and bracket . Had a oscilloscope on the sensor and it shows periodic hesitations.

Hopefully that's it then fix the engine light bulb and hurrah back on the road

Scarland
scarland
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Re: Hesitation and boging down

Post by scarland »

Hi Miklilmag

I just was curious have replaced the sensor on the front of the engine does the Dec 1988 635 have 2 flywheel reference sensors in the bell housing as well ??? these could also be the headache ???
Scarland
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miklilmag
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Re: Hesitation and boging down

Post by miklilmag »

[quote="scarland"]Hi Miklilmag

I just was curious have replaced the sensor on the front of the engine does the Dec 1988 635 have 2 flywheel reference sensors in the bell housing as well ??? these could also be the headache ???

Possible, anyhting they say!
scarland
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Re: Hesitation and boging down

Post by scarland »

to Milmlilmag

still no results have still to check fuel pressure reg and idle valve also the crank sensor I believe is the wrong sensor ( get a spike on the oscilloscope when running )for the front unit as I understand 1988 models have two one in the bell housing and one on the front crank. Does anyone have the correct part number for this one it seems there are ytwo types one long and skinny and the short fat ones which I believe are the one I am looking for help ???
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hornhospital
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Re: Hesitation and boging down

Post by hornhospital »

I'm not sure about the 88 model, but on previous models the front sensor serves no function other than for the diagnostic port. It isn't connected to the rest of the harness and has no effect on running.
Ken Kanne
'84 633CSi "Sylvia"; '85 635CSi "Katja";'85 325e "Hazel Ann"; '95 M3 "Ashlyn"
scarland
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Re: Hesitation and boging down

Post by scarland »

Can some one help me . I am in Australia . I am having trouble getting a front crank sensor for my BMW 635 1988 model, I am told the same engine is in E 34 and E 32 is the sensor the same ?? and can someone advise the actual part number please

Thanks Scarland
scarland
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Re: Hesitation and boging down

Post by scarland »

Hi I am still having periodic hesitation or missing or it just dies in my 1988 635csi . Put it into neutral and it starts up perfectly. I have replace fuel pumps, filters , temp sensor, main relays, new leads, new rotor cap and arm,new front sensor , had CSU checked and also flow box so what is the cause also had it smoke tested for leaks . Runs and idles beautifully but once running it starts and gets worse when it swarmed up out on the road helppppppp scarland
GazM3
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Re: Hesitation and boging down

Post by GazM3 »

Have u adjusted the tps. There is an audible click when it switches from control via the idle control valve to control via the ecu. What can happen is the adjustment is in range (just) when cold and then as it heats up it moves out of range and stumbles. It would be worth checking.
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