Which MAF for Impreza with a Z4 ecu
 

I have an UK spec Impreza with a few normal mods and fitted it with a Z4 ecu, it hasnt started or run right since i fitted the ecu but what code should the MAF have on it for use with the Z4? As I think I may need to change it

Thanks in advance

It should be fine, green labelled MAF I don't have the part number to hand. What are the symptoms of "not running right" and have you changed ANYTHING else at the same time like induction kit, dumpvalve etc?

It is a nightmare to start from cold and is hesitating between around 4k - 5.5k revs when booting it. It has a forge dump valve, sti intercooler, K+N filter, F.C.D, HKS Iridium plugs gapped to 0.7mm, lightened flywheel. Just normal mods really. It is a uk model fitted with a Z4 ecu. Ive changed the water temp sender with no change at all to the starting it starts perfect when warm though. Was thinking either the crank sensor or dodgy MAF although when i disconnected the MAF whilst running it did stall. Im really stuck with this one dont know what to try next.

I have fitted a Z4 to standard UK with no probs, everything else original. I did have some starting problems but that was down to my car not liking Tesco 99! Perhaps a knackered ECU.

Does the car still run perfect with Standard ECU fitted?

I have several ecu's that ive had on it in the past, one is a G7 which i believe is off a Legact turbo it starts perfect from cold with this ecu and I have a W9 and the Z4 which both have trouble starting from cold and the same running problems, ive had the Z4 ecu checked out and was fine on the test car. Maybe its the fuel i was using 97RON from a BP garage i think. Just swapped the Crank sensor for another second hand one i had lying around and starts abit easier but still isnt right, im thinking it might be a dodgy Crank sensor now but dont know what ohm reading they should give as standard
Any ideas?

According to the manual both should be 950-1250 ohms.

What's the starting problem like? fails to start?

Mine when cold would start but run at about 500revs, if you touched the throttle it would stall out, like it was running lean then after 5-10 secs it would climb to normal cold idle around 1400, would also drive like it was running lean for first couple of mins, we thought it was tesco 99 causing the problems but now i think i have a low fuel pressure issue that i'm just starting to rectify.

It sounds like you are getting a load related misfire, caused by failing coilpacks resulting in the hesitancy at 4500rpm (peak torque or there abouts). The starting may be linked to the coilpacks, but if it's a pain to start, I would check the cam timing is correct, you can do this just by removing the crank sensor and one of the cambelt covers (preferably the pass side one). Check that the when the mark on the crank wheel (the one inside the covers) lines up with the mark on the oil pump, that the cam wheel mark lines up with the mark on the rear cambelt cover.

The poor running off boost may be a function of the K&N induction kit, I would try refitting the normal airbox as a test.

Paul

FYI, i checked my cam/crank sensors today, both are 2.1k ohms, way above what the book says, crank is brand new!! perhaps they have improved them and the resistance has changed.

Didn't want you replacing both because yours read the same!!

Thanks for all the help your giving me guys this has me really stuck. Starting from cold just takes ages, I have to constantly keep tuning it over for a few seconds then turn key back to ignition then turn it over again untill it starts to come to life on its own then i have to pump the throttle to get it going. Also as soon as its running for about 10- 15 seconds if i touch the accelerator it almost stalls. After this its fine and idles fine even if I turn it off after just running for 10 seconds it will start no problem. I changed 2 coil packs afew weeks ago so they are fine. Im running out of ideas will check my cam and crank sensors now and see what they read.

Just checked my cam sensor that was 1086 ohms and the cranks sensor was 1094 ohms which sounds like they are pretty much perfect. As you have a manual does it say anything about checking MAF sensors in there? As this is my other concern and about the only sensor on the engine I havent checked. Also where did you get the manual from ive been looking for one for ages with no luck