MAF sensor replaced to cure hesitation, but now it's back :(
- Thread starter kpm197
- Start date
!interesting reading
http://mazda626.net/topic/38562-engine-smoothness-degrades-soon-after-ecu-reset/
http://mazda626.net/topic/38562-engine-smoothness-degrades-soon-after-ecu-reset/
Well to add to this. I replaced my battery the other day, not really to do with this specific fault, just that it didn't want to start the car after being sat there a week and I can do with out that during the winter.
Anyway. That made no difference. So it's not as thought the electric/ alternator is dropping out under hard acceleration and causing an issue.
Still noticeable. A morning/night when it was 3 deg air temp it felt good but I still managed to recreate the problem under hard acceleration in 4th. Still feels like the traction control holding you back or the car pausing for breath.
Still can't work out whether its air intake or fueling as being better when it's cold you would think it was air.
My fuel filter will be done during it's service in a month or so but not pinning any hopes on that by the looks of things.
For this many people to be having a very similar problem there must be some Vag owners who have fixed it.
For anyone asking I had a smoke test on mine and it was all sealed perfectly so no leaks in the breather system.
Anyway. That made no difference. So it's not as thought the electric/ alternator is dropping out under hard acceleration and causing an issue.
Still noticeable. A morning/night when it was 3 deg air temp it felt good but I still managed to recreate the problem under hard acceleration in 4th. Still feels like the traction control holding you back or the car pausing for breath.
Still can't work out whether its air intake or fueling as being better when it's cold you would think it was air.
My fuel filter will be done during it's service in a month or so but not pinning any hopes on that by the looks of things.
For this many people to be having a very similar problem there must be some Vag owners who have fixed it.
For anyone asking I had a smoke test on mine and it was all sealed perfectly so no leaks in the breather system.
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andrewkettle
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http://uk-mkivs.net/forums/t/420787.aspx?PageIndex=6
Long thread dealing with this slight hesitation at low revs issue probably every fix tried - looks like the rocker cover gasket could be a possible culprit.
Long thread dealing with this slight hesitation at low revs issue probably every fix tried - looks like the rocker cover gasket could be a possible culprit.
I took mine in the other week to a vag specialist for a cts and thermostat and whilst I was there I was explaining my car is to that smooth at low revs in traffic etc feels like it chugs and hesitates he said it sounds like the brake light switch,and to be honest it runs a lot smoother now but not sure if the cts or thermostat as helped more because it was running more around the 70 mark....
what systems were smoke tested just the breathers? Its really vac and boost that needs testing.
I would guess just the air intake and breathers then. Just to check. Would the rocker be part of the breathers?
What needs unplugging for the tester to be fitted? I may be able to guide them through it
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Just had this done and It seemed to be two different access points so i think vac is different. Theres lots of 1 way valves on the vac side so testing via intake might not cover all of it.
Bill runs a smoke machine so maybe give him a bell as he will know for sure.
I was having starting problems and they found 2 leaks on vac and boost. Only had it back 1 day so needs to adapt but so far car seems more responsive and cold start seems perfect. Hard to say if its your problem though.
Bill runs a smoke machine so maybe give him a bell as he will know for sure.
I was having starting problems and they found 2 leaks on vac and boost. Only had it back 1 day so needs to adapt but so far car seems more responsive and cold start seems perfect. Hard to say if its your problem though.
I changed my CTS for a genuine one, worked great for a couple of days, now it's no different
did you check out my link from further up the page- interesting theory on injectors and ecu trim levels
I read about the injectors. Thought there would have been more people suffering with something like that by now. If there's an easy way of testing them it would be interesting. Would you not see wetting on the spark plugs if it was over fuelling?
Can't see how a brake light switch would affect it. Anyone want to try that one??
Can't see how a brake light switch would affect it. Anyone want to try that one??
Been talking to some of the people on the Mk4 Golf forum. They have similar theories to the ones we have. The list of possible causes runs along similar lines that may indicate a Vac leak..... somewhere or a setting problem.
So, in no particular order:
Throttle body clean and reset
Vac pipes
Charge pipe/s
Rocker cover gasket
Any other possibly leaky gasket or pipe
CTS
Thermostat
MAP sensor
Now the last one is interesting as I found this for it's description:
MAP Sensor - The MAP sensor or the Manifold Absolute Pressure sensor is a sensor that measures the changes in vacuum pressure and sends a signal to the ECU. The ECU then calculates the engine load and calculates the fuel and timing.
Only problem is its a £70 part but can get for £47 with discount on ECP at the moment. Not sure if there is a way of diagnosing any potential fault on it??
I've just run the car with some super unleaded. That along with the colder temperatures at the moment makes the problem seem less noticeable (until it readjusts). My theory is because of the higher octane fuel its putting less requirement on the vac boost sytem so therefore not needing to put as much in to get the same kind of gains. When dropping back down to 95RON it requires the extra back from the system so shows up...... well thats a theory anyway.
I'm going down the lines of Vac system anyway for now.
List of what I've done so farin order (or time I had it replaced). Car has done 105K miles and is a 2003 model.
PCV pipes (Crankcase, lower & manifold brathers) - not done the very bottom plastic/ metal one yet.
MAF sensor replaced new bosch one
Throttle body clean and realign
New battery (unrelated fault but done recently)
CTS done with cambelt change at 60K ish
Thermostat replaced 2 years ago
So, in no particular order:
Throttle body clean and reset
Vac pipes
Charge pipe/s
Rocker cover gasket
Any other possibly leaky gasket or pipe
CTS
Thermostat
MAP sensor
Now the last one is interesting as I found this for it's description:
MAP Sensor - The MAP sensor or the Manifold Absolute Pressure sensor is a sensor that measures the changes in vacuum pressure and sends a signal to the ECU. The ECU then calculates the engine load and calculates the fuel and timing.
Only problem is its a £70 part but can get for £47 with discount on ECP at the moment. Not sure if there is a way of diagnosing any potential fault on it??
I've just run the car with some super unleaded. That along with the colder temperatures at the moment makes the problem seem less noticeable (until it readjusts). My theory is because of the higher octane fuel its putting less requirement on the vac boost sytem so therefore not needing to put as much in to get the same kind of gains. When dropping back down to 95RON it requires the extra back from the system so shows up...... well thats a theory anyway.
I'm going down the lines of Vac system anyway for now.
List of what I've done so farin order (or time I had it replaced). Car has done 105K miles and is a 2003 model.
PCV pipes (Crankcase, lower & manifold brathers) - not done the very bottom plastic/ metal one yet.
MAF sensor replaced new bosch one
Throttle body clean and realign
New battery (unrelated fault but done recently)
CTS done with cambelt change at 60K ish
Thermostat replaced 2 years ago
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