Accelaration and engine management problem possibly linked to the airflow sensor ?

[tony lucas]

iv just recently had my car a vauxhall astra 1.7 td serviced and now when i drive in any gear at approx 3000 revs i lose the ability to accelerate and the car will not go past 3000 revs the engine management light also comes on. iv had it on to the tester at a vauxhall garage but they can find no fault because this does not happen when the car is static and you rev it. its only when it is moving it happens. iv noticed if i disconnect the air flow sensor the car does more or less the same thing where it wont rev past 3000 revs and the engine management light stays on... Please help ?

[adamuser]

I have a feeling this is the throttle potentiometer. This tells the engine managment system the position of the accelerator. When broken it can think that the accelerator is not fully down when it is, and therefore not accelerate to its fullest. However this should come up on the EM System tester. Have the garage been testing it when the Engine management light is on?? I have had an intermittent problem with the throttle potentiometer whereby when the car is moving, it vibrates the unit and causes shorting out.

[tony lucas]

the management light doesnt come on when the cars just sat tickin over adamuser thats why the tester couldn pick up on the fault. yr idea sounds a good 1 cos obviously when the car is movin its vibratin however for instance if im in 3rd gear doin 30 miles anh hour at 2 - 3000 revs if it starts to happen i can accelerate past 3000 revs slowly and the management light goes off and the car pulls properly again. its when im doin 60 or 70 on the motorway at about 3000 revs that its causin most trouble bacause when it comes on then it wont allow me to accelerate past 3000 revs so my cars only doin 70 miles an hour max which is dangerous as well as annoyin if i need to pull out to overtake theres just no power there to do this

[BillyNoMates]

If the EM light is illuminating when driving, any fault code should be stored in memory.  This is so the Tech 1 analyser at the garage can read, and clear the fault.

However, I've had faults which weren't picked up by the analyser - faulty idle control valve (common problem) on a petrol engined Calibra. I would tend to agree with the throttle potentionmeter idea from adamuser.

 

 

[tony lucas]

gracios billynomates.  it seems strange if the fault is logged on the em memory why the robbin ****** at the garage found it necessary to take 28 of my hard earned pounds off me but still provided no answers. think ill buy a ford ! any idea if potentiometer probs are an expensive carry on or is it just another of the many wonderful sensors any car made after about 2000 seem to have on them

[BillyNoMates]

Hi tony, sorry for the delay - yes, I sympathsise with you wrt having to pay for finding nowt, been there many times. I never had any problems with the throttle potentiometer on a Vauxhall.

I guess as with the idle control valve - doesn't get picked up on the Tech 1 and yet it costs �140 a go to replace - buy one and problem eliminated for 12 months or so, the part itself could be pricey. Sadly I no longer have said Calibra or a Haynes manual to offer assistance in  how you might do further testing yourself. But then of course you are having problems with the 1.7Tdi engine so my information is probably not too relevant.

I have mentioned before here and it has certainly helped me out - you can buy a tester from Halfords for about �10. This actually picked up my problem which the Vauxhall garage's Tech 1 didn't.Might be worth a try.

Sorry I couldn't be of more help - good luck.