mokes

RPM surge when turning right

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Here's a weird one for you. I have always felt a sensation of rising revs on a particular bend on my way to work, but assumed it was my imagination.  Recently I have been looking at the gauge on this bend and it does rise slightly, accompanied by the engine note.

I have now noticed it happenng in certain conditions. They are - going around a right hand bend, usually on an incline and always at a tad over 2k rpm. The RPM and throttle position are the most relevant areas I've noticed as speed isn't usually relevant, but generally 40mph.

There was a sweeping bend recently where it happened and the revs rose by around 250rpm.

What do you chaps reckon?

It's a 1.6 automatic.

 

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No one?

I have checked hoses for leaks and the oil levels. Was thinking maybe the throttle pedal itself was at fault but doubt that.

In my opinion an increase in RPM would be due to:

Involuntary input at throttle ( electronic fault)?

Vacuum leak ?

Fuel pressure issue?

But why only on a RH bend???

 

 

 

 

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A couple of thoughts - which may or may not be useful to you :

When trying to identify a problem it is helpful to identify what the problem is and when it occurs - it is equally useful to consider what the problem is not and when it does not occur.

In your case - Since the problem only occurs when turning right there appears to be some sort of centrifugal force acting on a component which reacts by increasing RPM

I don't know enough about your car set up to point to specific components but I would be looking for a loose connection or component in the throttle and/or pedal areas which is just loose enough to respond when turning forces apply but which is not affected by the opposite turn or ordinary usage.

The only other thought I had was that I have heard in the past of cranks sliding in their bearings when worn and affecting sensors which could also throw up an electrical signal to increase revs OR it could be a duff engine sensor

Finally are there any engine fault codes recorded which might point in the right direction of the fault?

Hope that helps in some way

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Is it various RH bends or only that particular long, uphill bend?  I'm just thinking the EHPAS motor might be fighting a bit and requesting more rpm from the PCM.  I don't even know if the 1.6 auto gets EHPAS though or if it's just the old hydro pump?  Also seems odd that 2000rpm wouldn't be enough for the alternator to maintain enough charge for it.

I also wonder if you're wearing heavy boots?  You might be very slightly leaning/shifting to counter the centripetal corner forces and push the pedal a bit more without knowing?

 

Interestingly, I've known of a few RPM drops on right handers because the fuel pump & pickup is usually on the right and the fuel moves left and away from it.

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I don't know what style of auto box these have.

Years ago my brother had a Rover P5 3.5l V8 auto. It had a slow transmission fluid leak. We always knew when it needed topping up as on a particular left hand uphill bend it would lose drive for a moment (revs rose and car slowed) due to the fluid not being sufficient level for the pickup pipe due to the cornering chucking all the fluid to one side.

so is it the fluid level?

 

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Just a really outside chance, check your Crank Position Sensor. Mine was really strange- Turned out to be the plate that held it in had become unbolted from the engine casing and was free to move around..

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Hi chaps. I'll look at all the suggestions on my days off, but noticed that if does the same on left handers too. It may always have done but I've been really looking lately.

It does it on any bend that lasts more than a few seconds, often straight away as I turn the wheel at the right rpm and throttle position. 

Im not wearing heavy boots and very aware of keeping my feet in the same position. It was my first thought too.

No tranny leaks or low fluid. It was serviced recently, new fluid and filter. The old fluid was like new the chap said.

The increase in RPM means a boost in acceleration too, quite interesting on the long bend I mentioned.

Sensors...maybe. On some rare occasions it wont fire up on the first go, like the cam sensor is playing up.

Cheers

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Cam Position and Crank Position Sensors are a neglected and oft forgotten source of problems in modern engines

Plenty of stuff on the web on how to check them

Good Luck with the investigation

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I was wondering if it had cruise control, to see if it fluctuated then. 

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Not changing gear and no cruise. If I put it in 'manual' it still behaves the same within the same parameters.

Will need to get codes read but Id hate paying £50 to be told there is nothing there.

 

 

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Obd reader less than 20 quid from tunnelrat (recommended on here many times). Forscan free for windows, about 6 quid as an app for android/apple

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Hi..not getting notifications so slow to respond, but I didnt realise you could Forscan for free  I have an ELM127? reader but its pants on most cars I tried it on. I'll  contact tunnelrat. How do I ?

Wirey when wet...did your crank sensor cause surges at all?

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Cheers. Which is the best option for general use? WiFi  USB or the auto switch version.

My experience with ELM 327 is using a cheap clone which didn't really work, so any of these would be better I assume.

The WiFi one sounds good  as my laptop is not up to much, so is that ok for general use and I'm  not sure what  "high speed module " stuff is?

 

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15 hours ago, mokes said:

Cheers. Which is the best option for general use? WiFi  USB or the auto switch version.

My experience with ELM 327 is using a cheap clone which didn't really work, so any of these would be better I assume.

The WiFi one sounds good  as my laptop is not up to much, so is that ok for general use and I'm  not sure what  "high speed module " stuff is?

 

Loads of us on here have used oen of the Tunnelrat cables, they're definately the ones to go for.  I've got the Wifi one and the USB one, personally I'd say go USB as the wifi one can be a little flaky/less stable if your car is having electrical issues.

 

The "high speed" module stuff is basically just that Ford's gave to canbus systems instead of one big one like some manufacturers.  If you use a dongle that doesn't support the high speed bus, it just means you won't be able to see all of the modules and sod's law would make it so that the module that you need to see/reset is one of the ones on the high speed bus!

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Ok. I ordered the USB version.

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