Mrs Grouch's VW MKIV GTi is not well.
Discussion
I've just been out in Mrs Groucho's MK 4 1.8 GTi and all is not well. It seems to hold back very badly as if there is a serious fuel starvation thingy going on.
The problem seems to be intermittent, as this has happened before, but stopped when she put redex in with the fuel.
Any ideas as to the cause of this?
Cheers,
Grouch.
The problem seems to be intermittent, as this has happened before, but stopped when she put redex in with the fuel.
Any ideas as to the cause of this?
Cheers,
Grouch.
I think you guys are getting mixed up with the MAP sensor, which reads manifold absolute pressure.
The car will run with this disconnected, but it is a crude way of diagnosing it, because it could be the mapping that is faulty in the MAP part of the circuit, and not actually the sensor itself.
You cannot run the car with the airflow meter disconnected, it simply won't come off idle.
Proper diagnostic equipment is the only way to be sure with modern electronics.
Having said that, the most common fault with rough running on the VW 16 valve engines is oil deposits in the throttle body from the breather system, and it sounds like this is the problem here.
Take of your air filter casing and jam the throttle butterfly wide open, GENTLY!!
If you find that it is filthy and badly carboned, you have found the problem. Buy some carb cleaner in a high pressure aerosol and clean the deposits off with that and an old toothbrush.
She'll run like a bird after that.
The car will run with this disconnected, but it is a crude way of diagnosing it, because it could be the mapping that is faulty in the MAP part of the circuit, and not actually the sensor itself.
You cannot run the car with the airflow meter disconnected, it simply won't come off idle.
Proper diagnostic equipment is the only way to be sure with modern electronics.
Having said that, the most common fault with rough running on the VW 16 valve engines is oil deposits in the throttle body from the breather system, and it sounds like this is the problem here.
Take of your air filter casing and jam the throttle butterfly wide open, GENTLY!!
If you find that it is filthy and badly carboned, you have found the problem. Buy some carb cleaner in a high pressure aerosol and clean the deposits off with that and an old toothbrush.
She'll run like a bird after that.
Our TT ran just fine with the electrical connector to the air flow meter disconnected (or MAF or whatever else it is called). An exchange unit cured the mid-range performance problems.
IOLAIRE's suggestion sounds like a good thing to check first though. No point in paying out for something you don't need.
IOLAIRE's suggestion sounds like a good thing to check first though. No point in paying out for something you don't need.
Just to clear this up guys, a MAP sensor that reads manifold absolute pressure is situated in the inlet manifold tract AFTER the throttle butterfly and therefore reads the conditions inside the manifold which, on a normally aspirated car will vary from maximum vacuum to infinity according to throttle opening and conditions; on a turbocharged car this converts to pressure as the turbo builds up boost.
An air flow sensor will read the speed and volume of the air as it enters the inlet manifold tract BEFORE the throttle butterfly or turbo, usually near the air filter.
The problem nowadays is that there are so many variations on different systems according to spec that it's almost impossible to keep up with the variants without looking at a particular vehicle.
Running any turbocharged car with these components faulty or disconnected is highly dangerous and can result in fatal piston damage or worse.
You have been WARNED!!!!!
An air flow sensor will read the speed and volume of the air as it enters the inlet manifold tract BEFORE the throttle butterfly or turbo, usually near the air filter.
The problem nowadays is that there are so many variations on different systems according to spec that it's almost impossible to keep up with the variants without looking at a particular vehicle.
Running any turbocharged car with these components faulty or disconnected is highly dangerous and can result in fatal piston damage or worse.
You have been WARNED!!!!!
IOLAIRE said:
You cannot run the car with the airflow meter disconnected, it simply won't come off idle.
Proper diagnostic equipment is the only way to be sure with modern electronics.
You can run a car with the air mass meter disconnected it just reverts to its default value, if the new VW or BMW / Mercs which use ( Bosch units ) are guttless and show no fault codes, we disconnect the air mass if its running improves its always a faulty meter, the reason is they are self cleaning, upon starting a current cleans the carbon of the sensor wire but after a while they blow themself to bits.
thesilverfox said:
You cannot run the car with the airflow meter disconnected, it simply won't come off idle.
Proper diagnostic equipment is the only way to be sure with modern electronics.
You can run a car with the air mass meter disconnected it just reverts to its default value, if the new VW or BMW / Mercs which use ( Bosch units ) are guttless and show no fault codes, we disconnect the air mass if its running improves its always a faulty meter, the reason is they are self cleaning, upon starting a current cleans the carbon of the sensor wire but after a while they blow themself to bits.
I wish you people would read my posts properly.
For a start, an air mass meter is distinctly different from an air flow meter and works on a different principle.
Secondly, you have just stated that you check for a fault code first, then if no fault, replace the meter, which is exactly what I endorsed in my post.
You don't replace components first in the hope that it will cure the fault, you carry out the diagnosis first and that will lead you to the correct or probable fault.
If you disconnect an airflow meter from an early Motronic car, it will start, but will not accelerate from idle; it can't coz it has no signal to up the fuelling speed at the injectors.
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