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Vauxhall Astra - Thought it was just the MAP sensor

I have a Vauxhall Astra 1.6i GLS P reg. Here is the problem intermittently the engine management light would come on but there was no noticeable symptoms with the car so it was ignored for the time been, the light never came on again but the following symptoms were then noticed.

When driving the car it would suddenly feel like the engine was been held back and i had to rev hard to keep it from stalling, if the car did cut out it would then be hard to start again but after a couple of minutes it would start providing the accelerator was pressed to give it some fuel (new fuel filter fitted a couple of months ago so unlikely that), it would do this several times in the day but not as soon as you started driving the car only after a while or so.

I decided to have the fault codes read and was present when it was been done the device that was said to be faulty was the MAP sensor it said the voltage was too high so. Went to main dealer got a brand new MAP sensor fitted had the fault codes cleared drived it around a fair bit and everything seemed ok.

Last night when i was driving i noticed the same symptoms as before the new MAP sensor was fitted when pressing the accelerator there doesnt seem much power so kept revving it to prevent it from cutting out the problem is that there is no engine management light coming on now. Does anyone know what might be the problem with it now? the thing is that the fault is intermittant i would really appreciate any ideas as to what it could be.

Thanks in advance

du.

Reply to
du
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This a common mis-conception of people carring out maintenance of fuel injection systems. Reading out the fault codes stored in the system and being presented with a MAP sensor voltage high code does not implicitly mean that it is the MAP sensor at fault. There could be a fault with the wiring to the sensor (signal wire shorted to voltage), a problem with the input on the ECU, or even a mechanical problem with the engine causing an incorrect manifold pressure (air leak for example). The code being flagged up just means that the ECU has detected that the MAP sensor reading is out of permissible range for the prevailing operating conditions. It is up to the person diagnosing the fault to use the code as a starting point and then work from there to ascertain the fault.

For example, Vauxhalls with the X20XEV ecotec engine with idling problems would bring the EM light on, and report a fault code of Mass Air Flow Sesnor Voltage Low. There was actually nothing wrong with this sensor, it was the fault of a sticking idle control valve not opening, which allowed air flow through the engine to drop to zero (or near zero) and confuse the ECU.

As for your problem, I would check first of all that there are no air leaks on the intake manifold, that the throttle body is clean and the idle control valve is working correctly.

HTH

Anthony Remove eight from email to reply.

Reply to
Anthony Britt

You seem to know a bit about these engines. I've just replaced an engine in a 96 Omega and can't get it to start - no fuel pump running, no spark. Local auto electrician has read the fault codes and diagnosed the wrong crank sensor fitted - can't argue with this as I did replace it and the plug is different; seem 96 was a changeover year for the sensor.

However would this fault prevent the fuel pump from running at all? I understand it's supposed to run as soon as the ignition is switched on, but doesn't.

Reply to
Chris Bolus

The fuel pump should run breifly with igntiion on, then stop as the FPR clicks out.

Check for +12v at the coil pack pin 2 and if there is none, and no other engine actuator activity then the ECU isnt powering up, so you have no chance of fuel pump or anything else.

If the ECU is powered yet its not engaging the fuel pump, then you have an immobilizer problem, or you have connected the "starter energised" feed wire to the ECU at the starter motor to earth instead of the feed from the igntiion switch.

Tim..

Reply to
Tim (remove obvious)

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