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Discussion Starter · #1 ·
So basically my prblem is this.
If i start my car when its cold, starts up fine and all that, no EM light or anything strange on the dash. However when i get to about 3300-3600 RPM, doesnt matter what gear im in, the car kangaroos like ****. Enough to shake me about in my seat. This continues to happen until the engine has reached operating temp, and instead of it kangarooing i can just feel a loss of power, but when the engine is hot im able to power past it and into the 4000's+.
But when its cold it doesnt matter what gear im in, it physically will not go over 3300-3600 revs, it just kangaroos and i look like an idiot.
As an example it happened today on a dual carrigeway in 5th gear at 3300rpm, starts jolting around so i have to stick to 60mph.
Crankcase sensor fitted not long ago. Its been like this and has progressively got worse for about 3 months. I think i remember it starting to happen when i drilled my airbox. However no one else has this issue so i dont see why drilling the airbox should do anything.
My only theory is the MAF, i ordered a new one about 2 years ago off ebay and that recently packed in, so the mechanic salvaged an official Vauxhall MAF from an old corsa off the scrap and put that in about 3 months ago. So is it the MAF yet again? Or would taping over the airbox holes fix the issue? Its getting ridiculous and dangerous now.
Thanks
 

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Two things to try, which won't cost you anything to try.

Firstly I'd do what you suggest and try taping up the airbox.

Secondly, try disconnecting the AFM/MAF (whatever you want to call it) and try it. It will run, and if the problem disappears then you know what was causing it.
 

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Discussion Starter · #6 ·
But when its hot it runs fine just with a flat spot at 3500, i can still get 60+mph when its hot, no chance when its cold though.
And ill try disconnecting the MAF, but wont the car run terrible with it unplugged?
 

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But when its hot it runs fine just with a flat spot at 3500, i can still get 60+mph when its hot, no chance when its cold though.
And ill try disconnecting the MAF, but wont the car run terrible with it unplugged?
If you unplug the AFM then the car won't run as well as usual due it being forced into limp mode - but it ought to run reasonably OK.

The point is that if it runs consistently then it gives you an idea that the AFM could be the culprit. If you still have a misfire even with the AFM unplugged then you know it's something other than the AFM causing it. It's just a process of elimination - and trying it is simple and doesn't cost anything, so worth doing before you start messing about with anything else.
 

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OK - you've eliminated the most obvious suspects. When it starts jolting at around 3000rpm what happens if you floor the throttle? You said originally that you could 'power past' the hestitation. If that's the case I'd try cleaning out the EGR valve - not promising that's what it is - just suggesting a logical next thing to check. Again, it's a check/action that won't cost you anything.

Just worth checking the obvious - are the air and fuel filters clean?
 

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have you tried going up past 3300rpm in neutral? see if you get same responce from engine. could have something to do with the load of the car but then again you wont have a MAP sensor so i don't know how that could measure up to anything.

just babbled on and got lost in my own words there, try it anyway though!
 

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Discussion Starter · #11 ·
OK - you've eliminated the most obvious suspects. When it starts jolting at around 3000rpm what happens if you floor the throttle? You said originally that you could 'power past' the hestitation. If that's the case I'd try cleaning out the EGR valve - not promising that's what it is - just suggesting a logical next thing to check. Again, it's a check/action that won't cost you anything.

Just worth checking the obvious - are the air and fuel filters clean?
If i floor it it jolts even more when its cold. When its hot it hesitates like a normal flat spot then powers over 3000rpm.
Yes air and fuel filters are clean
 

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because the dont drive the car in the mot they just let it run and dont rev it much if i recall
 

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mine has the same problem near enough but my car when cold runs like a dream but soon as it gets hot it jolting at 3500-4000 revs when its cold it gets up to like 65mph when hot it will get upto 60mph if i push it any one found a solution
 

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I would Try Your Cam Shaft sensor i heard they can Go faulty

Camshaft controls Your Rpm
More throttle Alerts the sensor to Letting in more Fuel And sucking more air :) I know you know that...

It could be faulty
I Just replaced mine when it was starting Sometimes and starting not
now it starts every time

Also when it started the Throttle was all over the place!
good luck
 

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If you've had recently replaced the timing belt or recently bought the car, there's a chance they didn't replace it properly that could also send the car into limp mode too. Especially if the car is surging at 3500 rpm and throwing and error code, but if it's not surging, check your air intake system (intake tube, air filter, idle control valve, throttle position sensor...)
 
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