Odd rev behaviour on startup....any ideas? - MG-Rover.org Forums
 
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post #1 of 17 (permalink) Old 18-05-2015, 11:06 Thread Starter
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Odd rev behaviour on startup....any ideas?

Just looking for a bit of advice on what might be causing a minor irritation of late. Started over the last few weeks. Car was fully serviced by MGRMM towards end of last year and has been in use daily since, covering a small mileage each day.

Basically what is happening is only upon the first start of the day, and then not even on every start.

The car starts fine with no hesitation, I reverse it out of the garage, get out to close garage door and return to the car to find the revs going up and down in the 200-1500 range intermittently and occasionally, this is followed by a total loss of power and the engine cuts out.

She starts up again just fine, and this behaviour is non-existent thereafter - it's just bugging me as to what is causing it - as I am no mechanic by a long chalk.

So, any of you guys have any ideas for me to maybe resolve the issue?

TIA,
Steve.

Last edited by steviejones133; 18-05-2015 at 11:14.
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post #2 of 17 (permalink) Old 18-05-2015, 12:32
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When you reverse out the garage... are you on an incline? I would look at simple things first... like fuel.
Any chance you could have water in the tank?
Blocked fuel filter... lines not on fuel filter correctly...perhaps getting air in...
Fuel pump... (I am not sure where it is on MG's (only had mine a week) is it earthed properly..

I would check fuel/lines/pump first to rule that out..before looking at electrical/mechanical..
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post #3 of 17 (permalink) Old 18-05-2015, 13:42
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Try a TPS reset first (Throttle Position Sensor).
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post #4 of 17 (permalink) Old 18-05-2015, 21:10 Thread Starter
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Well, yeah....the garage is on an upwards incline so that the rear is lower than the front on reversing out. I doubt that there is water in the fuel tank. The fuel filter/pump are as per when I bought the car - don't recall them being touched in the service by MGRMM, I'd have to check.

I have been using that Redex fuel additive every full tank (for petrol injectors) so I presume that the lines/injectors are okay, but of course I could be wrong.

I think I will try a TPS reset as suggested and see what gives. Same thing as here, right?:

Throttle reset procedure why/how
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post #5 of 17 (permalink) Old 18-05-2015, 21:59
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Check the engine coolant sensor the plug may be loose or the sensor may be faulty. You will have to lift engine cover to check plug

A scanner is best way to check sensor it should show approx ambient temperature when you start the car
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post #6 of 17 (permalink) Old 18-05-2015, 22:16
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Quote:
Originally Posted by plezier View Post
Try a TPS reset first (Throttle Position Sensor).
Do this .
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post #7 of 17 (permalink) Old 20-05-2015, 20:09 Thread Starter
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Well, followed the TPS reset procedure tonight after a decent run out. She's in the garage now and I guess we'll see if it has helped in the morning. Must admit, she sounded a bit more tuneful for some reason after doing it......placebo maybe.
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post #8 of 17 (permalink) Old 20-05-2015, 22:48
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If that doesn't work, check the air intake system.

One of mine did this and garage after garage tried everything, new sensors, the lot.

Eventually a mechanic I got talking to fixed it in minutes. Somrthing in the vicinity of the throttle body hadn't been tightened properly and a quick bit of attention from a screwdriver sorted it.

Maybe with yours it's because somethings not tight and it only manifests its self when the plastic, or whatever is cold and inflexible.
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post #9 of 17 (permalink) Old 20-05-2015, 23:35
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Vacuum leak?
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post #10 of 17 (permalink) Old 22-05-2015, 12:45 Thread Starter
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Just to update - up until now, the TPS reset seems to have done the trick. I'm gonna keep an eye on it and see how she goes...fingers crossed that will be that.

Thanks to everyone for the advice, I'll be back if it returns!
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post #11 of 17 (permalink) Old 18-06-2015, 18:29 Thread Starter
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Well, the odd behaviour has returned. I've since noticed that the same drop to very low revs (around 100) also occurs when I'm dipping the clutch to change down in 2nd/1st gears.

Last October, she had a full service with new plugs, fuel filter etc - also had a small oil leak from the cam cover fixed that was leaking into one of the plugs. Not sure if that has reappeared or if could be a potential cause if it has.....I have noticed the very occasional 'pop' from the exhaust (misfire?) however, that only ever happens once and not really that often if it does happen at all - generally just after started if she does 'pop'. Now, the odd clutching behaviour makes me think it's something else, but I'm no grease monkey.....



Any further ideas? - apart from this behaviour, she's running really well.....
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post #12 of 17 (permalink) Old 18-06-2015, 19:03
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I can tell you its not the plugs, the coil packs or the two plug leads. It is not the tps sensor or the aits sensor or the pre cat sensor.

I know because I have replaced all of these attempting to stop this behaviour. Eventually it will misfire on one cylinder and stutter on pulling away.

When mine was last in for an mot 2013, he noted the engine light was on and the mechanic read the fault and got the same result as me- misfire on no3 cylinder! He cancelled it, redid the mot and it was fine. He pulled it off the ramp and it came back on! I told him what I had so far replaced and his advice was to get an auto electrician. It is one of those faults that you can chase forever and replace everything, but it will still come back.

My TF has been parked in Spain ever since the mot ran out last November. I suppose I should really get around to sorting it out and making it roadworthy for over here!
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post #13 of 17 (permalink) Old 18-06-2015, 19:47 Thread Starter
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I've not got any lights lit on the dash when this happens, nor have I ever had any warning lamps lit.

As it happens, just been to the chippy in her and as reversing down the drive, she cut out after dipping the clutch while reversing....so, I took her for a blast to get her up to temperature and I have done another TPS reset - this time, followed a different procedure of stomping the accelerator into the carpet 5 times in 20 seconds before turning back off. Let her stand another 30 seconds and fired her up again.

Instantly noticed smoother revs and a much steadier return to normal idle after revving her up a bit.

God knows if that will last - the morning will reveal all I guess.....
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post #14 of 17 (permalink) Old 25-07-2015, 17:38
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Quote:
Originally Posted by steviejones133 View Post
I've not got any lights lit on the dash when this happens, nor have I ever had any warning lamps lit.

As it happens, just been to the chippy in her and as reversing down the drive, she cut out after dipping the clutch while reversing....so, I took her for a blast to get her up to temperature and I have done another TPS reset - this time, followed a different procedure of stomping the accelerator into the carpet 5 times in 20 seconds before turning back off. Let her stand another 30 seconds and fired her up again.

Instantly noticed smoother revs and a much steadier return to normal idle after revving her up a bit.

God knows if that will last - the morning will reveal all I guess.....

So did you cure the problem or did it return ???
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post #15 of 17 (permalink) Old 25-07-2015, 20:39 Thread Starter
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Originally Posted by I.Am.Spartacus View Post
So did you cure the problem or did it return ???
It still happens intermittently. To be honest, I haven't done any exploratory fixes other than the TPS reset which does not seem to hold. Not being very savvy under the bonnet (or boot lid), I'm not really sure what to look for or how to attempt to resolve the issue.

If there are any 'how to's' or ideas that I can try to follow instructions for, I'm all for giving them a whirl.......
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post #16 of 17 (permalink) Old 26-07-2015, 12:59
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Hiya, you say the plugs an two leads have been replaced, why not all 5 leads ? Has anyone checked the distributor cap and rotor arm ? Any minor looking abnormalities in either will cause misfiring..
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post #17 of 17 (permalink) Old 26-07-2015, 15:09 Thread Starter
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Originally Posted by cars and bikes View Post
Hiya, you say the plugs an two leads have been replaced, why not all 5 leads ? Has anyone checked the distributor cap and rotor arm ? Any minor looking abnormalities in either will cause misfiring..
I had the plugs changes during a service, but not the leads - or distributor. What 'abnormalities' would one look for in the above?
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