Merv

iTrader: (12)

MY04STi JDM jerky on lift off and when holding steady speed ie 30mph in 3rd.

Had the car checked at a garage and found that the MAF voltage is reading 0.98-1.02v at hot tickover,checked for air leaks,replaced MAF and refitted OEM dump valve,but still the same.

The car is producing full boost and running sweat other wise.

Anyone had a problem like this before?

Cheers
Merv

GazJenno

MAF voltage isnt going to be very high at tick over .... you should rev it hard when testing the voltage and it should peak at 4volts +

Gaz

Merv

iTrader: (12)

The garage has checked the voltage at different revs and has found the low voltage at lower revs is making the map run rich which is causing the jerking.

c_maguire

But a lower MAF voltage indicates less air flow to intake which would make the ECU lean off the mixture not richen it. On a tuned car like yours an under-reading MAF should show up by the car holding back under high boost.
Sounds more like O2 sensor to me.
Kevin

Merv

iTrader: (12)

New 02 sensor fitted.

silent running

More likely a throttle position sensor problem IMHO. Around 1v at idle isn't that low for a MAF. YOu'd think that the TPS would be the FIRST thing to check, not the last, seeing as seems to be a throttle position related problem?

Merv

iTrader: (12)

I have no faults showing on the PSi3 ecu monitor.

Is the TPS an open or shut switch?

How can I check it's working?

Thanks
Merv

silent running

No, it's a variable resistor, basically. I can't remember what the exact output voltages are off the top of my head, but there is definitely a range that it should go through from closed to wide open. I think like many engine devices it takes a 5v input from the ECU. TPS is one of the inputs that keeps your car running, so yours is definitely working; just perhaps not very well. You can adjust the voltage range by loosening the screws and twisting it one way and the other.

Merv

iTrader: (12)

Ok thanks.