map sensor question

[dmclaude]

I'm in a bit of a pickle. I've got me an older Daihatsu GTTi which are awesome little 1.0 litre turbocharged beasts, but this bugger has a persistent issue with holding idle revs particularly when the aircon is turned on. Mechanic tells me it is a map sensor (or pressure sensor). I called round to the local dealers who want silly money for one flown in from Japan.

So here's my question : can I replace the stock map sensor with a generic 3-4 bar map sensor (still with the stock ecu), or can I use this excuse to upgrade to a piggyback ecu + generic map sensor and will the car still run properly. In other words, does the function of the piggyback ecu actually replace the function of the stock ECU and the requirements with relation to the map sensor readings?

Appreciate the help and assistance of the great forum gurus .

Tone.

[DVandrews]

Piggy back ECUs normally utilise the engine telemetry from the existing ECU. You would need the tech specs for the map sensor in order to find a replacement, bear in mind that most MAP sensors will handle lower than atmospheric up to atmo, only those made for turbo/supercharging will handle pressures greater than atmo.

Dave

[jimbob82]

are you sure/is your mechanic sure it's the map sensor? it's often the coolant temperature sensor that gives idle trouble like that...

[stevieturbo]

dmclaude said:

I'm in a bit of a pickle. I've got me an older Daihatsu GTTi which are awesome little 1.0 litre turbocharged beasts, but this bugger has a persistent issue with holding idle revs particularly when the aircon is turned on. Mechanic tells me it is a map sensor (or pressure sensor). I called round to the local dealers who want silly money for one flown in from Japan.

So here's my question : can I replace the stock map sensor with a generic 3-4 bar map sensor (still with the stock ecu), or can I use this excuse to upgrade to a piggyback ecu + generic map sensor and will the car still run properly. In other words, does the function of the piggyback ecu actually replace the function of the stock ECU and the requirements with relation to the map sensor readings?

Appreciate the help and assistance of the great forum gurus .

Tone.

I dont get the question. Are you saying it has a high idle when the aircon is turned on ? This would be totally normal.

And you'd need to be sure about the abilities of your chosen piggyback before splashing out.

As for the problem being a map sensor, if there even is a problem, I rather doubt it is the problem. And a map sensor is pretty easy to test with a mityvac and/or pressure source and a voltmeter.

But no a generic sensor will not work with your factory ecu.

[dmclaude]

I should clarify. The idling problem is that when I turn on the aircon, drive for a few minutes and come to a halt, the engine will drop revs until it stalls (I will usually heel and toe it at a traffic light to keep it from stalling). It is pretty intermittent - during a 15 minute drive, it will drive normally for most of the time and try to stall say around 3 times or so, but you end up being on edge the whole time!

I think the mechanic did test the map sensor, and believes that is the issue. The last owner said that his old mechanic just "tuned" around the intermittent problem (I have no idea what that means). My mechanic tried cleaning the sensor (again, no idea how you clean a map sensor), but no joy.

My intention was to just get a 3 bar map sensor (oem is 2 bar) and take it down to a tuner and just ask him to remap to the new values from the 3 bar map sensor, but I'm not sure that can be done based on what I'm readin gnow. Failing that my only option is to get one from a breakers, but these little buggers are darn rare here, so I might have to buy from an overseas breaker (and take a chance on reliability).

Any thoughts guys? Really appreciate the assistance!

[neiljohnson]

Map sensors tend to be fairly generic so will likely have been used on other cars get the make (Bosch webber etc) & google it hopefully its been used on something more mainstream & easier to get hold of

[stevieturbo]

I'd have someone competent test the map sensor. I really doubt it is the problem.

As for simply remapping your ecu to allow another map sensor. That's being a bit hopeful.

Can your ecu even be remapped ?