Who Can work this out?

93 WRX std + Decat.
I have had this problem for a few months and will be going to Pro Sport on Sat to hopefully sort out. But before I do has any one any ideas?

Problem:-
1) Seems to miss slightly on tickover and alot on slight throttle.
2) Using mega amounts of fuel -10mpg not hard driving!
3) Runs fine after 2500 revs.
Changed all coil packs, cleaned Maf and changed lambda sensor.

Reset ecu at home (cold engine) still same.
Reset ecu on select monitor(hot engine) problems solved then degraded
back to same problem.

My theory = Lambda sensor is not working correctly -cold
when ecu is reset when engine is hot the lambda sensor is
hot and the ecu reads it ok and sets the fueling and stops the overfueling.
When the lambda sensor is left to cool the ecu then starts to overfuel
as it starts to missread again!!! New lambda sensor broken.

What does anyone else think?

Sorry if anyone fell asleep.
Cheers

WW

 

Is the lambda a genuine part (ie. with the correct connector fitted to it from new) or is it the universal part?

If it's the universal part, then check the connections very carefully, and if possible get them soldered up.

The lambda sensor needs to have a very good connection - there can't be any resistance in the wires. A lambda sensor outputs a voltage between 0.1 and 0.9 volt, according to the exhaust gas mixture (0.5v is 14.7:1 AFR) so even a very small disturbance to this can have a huge effect on the amount of fuel used. Up to the point where you get better MPG by uplugging it!! Also check the wires that go to the heater in the sensor. These heaters can go wrong too, causing a similar problem.

Have you got access to a select monitor? If so then check the AF correction parameter to see if the car is always adding fuel or if it's not making any corrections at all...

Sorry I can't be more help - I think this is a case of playing with spares (preferably borrowed ) and a select monitor until something turns up.

 

It's a Universal part so could well be the wiring.

I'm going to prosport on Sat so they should sort it (hopefully)
Just wondered if anyones else had similar probs?

 

Dont worry about it, just drive it nice and slow

i had no end of problems with my scoob, funny intermitant misfires etc

Prosport sorted it in less than an hour and other bits too, top place.