Join Date: Oct 2013
Location: France, Metropolitan
County: Hauts de Seine
Tales of an overfueling GT JTS 2.0
It looks like my selespeed GT JTS 2.0 is overfueling and has very poor mpg (2004, 98K kms). There is also quite a lot of white smoke coming out of the exhaust for the first 10 minutes. This is normal as per the weather, but I feel like there's more than there should be.
At the moment, I'm doing around 14/15 l.100km (15.6mpg). I'm mostly driving to and from work, in the city, with cold engine most of the way (6km distance) and with hills, so I'm expecting a poor mpg, but not that bad.
A couple weeks ago, I had an engine light on and MES indicated a misfire on cylinder 2. After clearing the error did not appear again but to be on the safe side, I changed the relevant coil and all the spark plugs.
When changing the plugs, I realized the previous ones where covered of black powder (carbon) indicating the mixture is too rich. (those plugs were only a year old by the way).
After some reading on the internet, I took the car for a quick run with MAF disconnected to see if there was any changes. There was not. So I changed the MAF last week for a new one (not bosch original though), did an ECU reset and the car was running much much better. Less smoke and much more responsive. MPG was still as bad though.
Yesterday I had another engine light popping up. MES indicated a Mixture Correction (multiplicative) having reached it's upper threshold. I cleared the error and it did not come back yet.
Anyway the problem is still here: too much smoke on IDLE (I sometimes can't see the car behind me when sitting at a red light, the smoke seems fine while driving though). And most importantly, a exceptionnaly bad MPG.
I've driven back from work logging lambda values, air quantity and injection time today. The drive started with an almost cold engine (driven 3.5 hours earlier), and was 'enthousiastic' (aka, neither calm nor frantic). Unfortunately I haven't logged the RPMs. Those were around 2/2.5K most of the time, with accelerations up to 5K max.
I don't expect the lambdas to be faulty since they were changed by the previous owner about a year and a half ago. But I'm not really sure on how to interpret the data. I've read somewhere the MAF should range within 12kg/h on idle, up to 170kg/h around 5K rpms. The log shows peaks to 380kg/h, is this realistic?
Anyway, any help or opinion would be highly appreciated on this! I'd love to make that fantastic car run as if brand new!
PS: Engine temps is fine, the thermostat was changed a few months ago and the temp does go up quickly and stabilises fine at 90°C.
Last edited by TheDude510; 12-02-14 at 12:34.