M44: Intermittent hesitation while driving

gjm

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Our daughter's car has decided to demand attention. On a Sunday, of course. Just after we'd decided to sell it. (When else??)

While driving at a constant speed and throttle position, the engine will hesitate. It is as though it is running out of fuel - there's no warning lights (and 3/4 tank of fuel). The hesitation will last from a fraction of a second up to 2-3 seconds, during which no throttle activity makes any difference. Then the engine will pick up again and run as if nothing is wrong. No touching the ignition key, no gear changing - no action taken and it'll suddenly be fine. And then, after a random period of time, it'll cut again.

Perhaps more accurately, it is as if the fuel supply or the ignition just cuts out for a brief period of time.

It might do this several times in a minute, or it might not happen at all for several minutes. It happens under acceleration as well as under constant throttle.

When ticking over, the 'hesitation' can be enough to stall the car. Tickover - idle - is typically very (very) slightly rough but I had put this down to it being a few rpm below ideal idle speed rather than any significant issue.

When stationery the engine will typically rev freely and without problem. We have sat in the car with the engine idling for 10 minutes without an issue.

I've not been able to read any codes - I was recently made redundant, and the laptop went at the same time the job did. I do have an older Compaq which I'm waiting for a PSU for, but (of course) that's not arrived yet. I'll obviously check codes ASAP.

Any ideas? Checking the spark plugs has been suggested but I can't see how that it is going to cause a complete cut isuch as we are experiencing. Given circumstances cheap fixes rather than random replacement of expensive parts is much preferred! I was thinking of starting with a fuel filter, or fuel pump relay, given I've not replaced those yet.
 

colb

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Pretty sure you will have codes set when you manage to get them read. In the meantime whip the plugs out and have a look what they are like, sounds like a plug or ignition lead breaking down causing the misfire, maybe a dodgy coil as well.
Check all the rubber hoses on the inlet side for any splits that could cause an air leak, replace any that have holes or splits in them.
 

Ianmc

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Sounds like the camshaft sensor to me.:thumbsup:
 

hard top

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Daft question maybe but is the car overheating?
My 3 series BMW did something similar and that was what was causing it.
 

handsomejackuk

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get an obd bluetooth reader and a round socket convertor if you already have a mobile phone you can easily read the codes using the torque app and monitor a load of things too like real engine temperature as appose to what the dashboard guage tells you. you can also see intake etemperature, short and long term fuel trims boost / vac pressure, 02 sensor values in realtime.. cost you about £20 tops.. that is providing you have an android phone to run the app...
 
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gjm

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Pretty sure you will have codes set when you manage to get them read. In the meantime whip the plugs out and have a look what they are like, sounds like a plug or ignition lead breaking down causing the misfire, maybe a dodgy coil as well.
Check all the rubber hoses on the inlet side for any splits that could cause an air leak, replace any that have holes or splits in them.
Will do.
It's not so much a misfire, as a 'doesn't fire at all' - when it happens, it is as though something has temporarily - momentarily - turned off all four cylinders simultaneously.
It is a problem which has happened suddenly. No issue whatsoever, then one time out it happened several times.

Sounds like the camshaft sensor to me.:thumbsup:
I was kinda hoping that's not the case, but could be... :grumpy:

Daft question maybe but is the car overheating?
My 3 series BMW did something similar and that was what was causing it.
No indication of overheating. Everything looks fine. Nothing amiss. Except the engine. :(

get an obd bluetooth reader and a round socket convertor if you already have a mobile phone you can easily read the codes using the torque app and monitor a load of things too like real engine temperature as appose to what the dashboard guage tells you. you can also see intake etemperature, short and long term fuel trims boost / vac pressure, 02 sensor values in realtime.. cost you about £20 tops.. that is providing you have an android phone to run the app...
I'm using a borrowed phone (that went with the job too) but it does have Torque Lite installed. And while I don't have a bluetooth reader, it is something that would be useful.

Thank you. :happy: I've been having a read, and I do like the forum!
 

colb

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Likely its going to be the camshaft sensor or crankshaft sensor breaking down from your latest description, code will most likely have been set for the offending item.
 

gjm

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Likely its going to be the camshaft sensor or crankshaft sensor breaking down from your latest description, code will most likely have been set for the offending item.
A very reluctant agreement from me... (I wanted to dislike your post, but it's a bit soon for me to do something like that!)

Crank sensor is around $200 here; cam sensor about half that. Definitely worth trying to track down which one is the problem rather than randomly throw money at it.
 

DavidM

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Welcome from Ireland! In addition to the above - a quick check to ensure all leads are pushed firmly home. Hope you sort it soon.
 
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gjm

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Welcome from Ireland! In addition to the above - a quick check to ensure all leads are pushed firmly home. Hope you sort it soon.
Thank you! I hope it is sorted soon, too!
We've had a bit of a run on car problems recently - anyone got a 'how to' for bleeding the fuel system on an E46 320d (M47TU) ? Replaced the fuel filter, and it's not run since. :(
 

Slam

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Hi and welcome from London, bad luck comes in 3s !!
 

Mint

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Hi @gjm,:welcome: to the forum from me too in Staffordshire, UK. Hope you get your problems sorted soon, definitely need to read the codes.
 
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Shelly

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:welcome: Hi and welcome from me too :coolsteer)
 
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MartinN

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welcomke from Hertfordshire, hope you shake the gremlins out of the Z, it looks like a sunny weekend is coming!!
No use with Diesels but is there a schrader valve or some thing like it near the fuel filter or even a thing like a blood pressure pump to re presurise the filter?
 
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Jack Ratt

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Hello and welcome to the forum
 
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Brian4

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Thank you! I hope it is sorted soon, too!
We've had a bit of a run on car problems recently - anyone got a 'how to' for bleeding the fuel system on an E46 320d (M47TU) ? Replaced the fuel filter, and it's not run since. :(
Title says its for an E90 but looks as if it is the same engine code re diesel priming.
https://www.pelicanparts.com/techar...UEL-Diesel_Engine_Fuel_Filter_Replacement.htm

I read a thread some where about running the pump under the rear seats from a 12v supply to fill the filter.

When I changed the filter on our petrol Z3 it takes quite a while to fill the filter.
 
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gjm

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Title says its for an E90 but looks as if it is the same engine code re diesel priming.
https://www.pelicanparts.com/techar...UEL-Diesel_Engine_Fuel_Filter_Replacement.htm

I read a thread some where about running the pump under the rear seats from a 12v supply to fill the filter.

When I changed the filter on our petrol Z3 it takes quite a while to fill the filter.
There's three pumps in the 320d - the lift pump in the tank, a mid-pump to raise pressure, and the high pressure pump on the engine. There's a decent flow of fuel from the front of the mid-pump.
I cracked the fuel feed to the injectors (remove inlet manifold first!) and there is diesel there, too, but not at what I would consider any pressure.
There's no DDE codes for the engine whatsoever. (I was able to get this car read, but didn't have a round adapter for the Z.)

I'll have a read through the link. Hopefully it'll help!
Thanks.
 
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t-tony

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You can run the tank pump through a code reader, if it's up to it, to prime the fuel system. An alternate option is to spray brake cleaner (in a very fine mist) or similar into the airbox whilst cranking the engine to fire the engine.

Tony.
 

gjm

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I've successfully confused this thread!
OK - Z/M44. Took it for a drive this morning. Absolutely no problem whatsoever for 15km into the nearest town. Pulled up and the engine stalled, but as I was stopping anyway... Hmm.
Came out. Started first turn, then stalled. Continued to chug, splutter and generally not be happy while I moved to another stop on my errands. Coughed and spluttered - I was holding the throttle and the brake which kept the engine (barely) running while pullinginto and out of a parking space.
Drove home... Absolutely no problem at all. Again.
Definitely candidate for code reading, so it'll have to be parked up until I can sort that.

E46 will wait 'til my frustration levels have dropped slightly. ;)

@Slam : bad luck comes in 3s...? The alternate car, a W126 S-class Mercedes, stank of petrol when I started it this morning... :inpain:

In better news, I've been offered a job at a local Repco store. :eek: For those unfamiliar with them, think Halfords or similar. I've been there a few times over the years and the manager overheard that I was out of work, and asked if I'd like to do something with them. A few hours, a day, a few days, part time, full time, my choice. Even suggested it'd be something I could do to just keep my brain going and get out of the house for a while, until I found a 'proper' job! Pay is terrible, but there are discounts on parts... Hmm. Certainly something to think about.
 
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