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Car Forum / Nissan / Nissan Maxima / July 2006jecs air meter
I'm posting from UK, I have a 94 Maxima with 118k miles which has an erratic fault. Apart from this the car is in good order. The symptoms are good performance from cold but misfires and poor response to the throttle as it warms up. Suggesting good open loop running and a fault as it goes into closed loop. The exhaust gets very hot and it has just scraped through our annual test with a high lambda reading, suggesting un burnt fuel is carrying over and being burnt in the exhaust. The problem is getting worse and yesterday it went into "limp home" mode again, with revs limited to 2000. I've checked the flash code and got a code 12, mass flow meter or circuit fault. On clearing the code and starting from cold this morning there is no problem and the fault codes are clear. The mass flow meter has 4 wires, white+black, black, black then white. The two black wires show about 4 Ohms resistance to earth and when the ignition is on the white+black terminal carries battery voltage. Ignition on and engine off the signal (WHITE) gives .3V between it and ground, at idle 1.5V and with the torque converter stalled at 2500rpm and full throttle 2.8V. So on the surface it appears to be working. Anyone with any ideas what next to look for? AJH >I'm posting from UK, I have a 94 Maxima with 118k miles which has an >erratic fault. Apart from this the car is in good order. [quoted text clipped - 25 lines] > >Anyone with any ideas what next to look for? See here: http://www.cardomain.com/ride/748507/9 Al Moodie. >>Anyone with any ideas what next to look for? > [quoted text clipped - 3 lines] > >Al Moodie. Very nice and comprehensive, is it your site? Thanks. It looks like I have a lot of reading to do. Recent drive out after cleaning the air flow meter contacts and clearing the code still gave misfire and loss of throttle response plus popping in the exhaust. On returning home codes are 55= normal. It begs the question is there a scanner that plugs into the OBD1 interface that brings these real time codes to where they can be seen? AJH >>>Anyone with any ideas what next to look for? >> [quoted text clipped - 5 lines] > >Very nice and comprehensive, is it your site? No, I believe it belongs to Wiikinki, I have just seen it referenced so many times here I remembred there was a page on MAF. Al Moodie - When was your last ignition tuneup? Plugs, wires, cap, distr grounding=campos signal... - is O2 signal ok? =up/down 0~1V Now pls you tell me the best EU place to purchase spares. >- When was your last ignition tuneup? Plugs, wires, cap, distr >grounding The first thing I did was replace the ignition components, plugs, leads and distributor cap and rotor. Next there was a slight manifold leak which I thought might be letting air into the exhaust, two studs helicoiled and gasket replaced. Neither made any difference. >=campos signal... Please expand I don't understand this. >- is O2 signal ok? =up/down 0~1V I have only just been given the car so the OBD1 output was my first check, I do note that the ecu code selector screw goes past a hard spot so may have been forced in the past. I will look for the pinouts for the lambda sensor or back probe them and readout from a DMM whilst driving. >Now pls you tell me the best EU place to purchase spares. From quick searches for air meters and ecus it looks like the secondhand market in the US is the most plentiful source UK Nissan OEM parts are more costly than the car is worth. Is there a straight forward way to force the ecu to remain open loop? AJH ..The first thing I did was replace the ignition components, plugs leads and distributor cap and rotor... I will look for the pinouts for the lambda sensor or back probe them and readout from a DMM whilst driving... Yes, I keep the Maxima CDomain account purring New soot hoses (sold as ign wires) like cap can possibly be worse than old. Take care. First thing for me was REAL wires see page12 Eh 'Êmpos', ... neither do I understand that - at least I tried to write 'campos' signal ... (distributor grounding bad, signal warped, see my CDomain page 10.). If this signal is out, ECU falls in safe mode Yes there are also OBD1 readers, but I havent found any with decent pricing. Pls tell me where.. "a straight forward way to force the ecu to remain open loop? - digital 1/0 gas pedal: drive always WOT - bypass engine temp sensor with 2-to-3k resistor =keep ECU input 'cold'. Consumes more gas as O2 will be bypassed That ECU selector sw might be broken =your problem? Take it out and find a workin sw to solder&replace O2 can be probed from ECU pins or under the hood while idling (warm) -- Wiikinki www.cardomain.com/ride/748507/ >The problem is getting worse and yesterday it went into "limp home" >mode again, with revs limited to 2000. > >I've checked the flash code and got a code 12, mass flow meter or >circuit fault. As a follow up: I have been running through the connectors to make sure they have good contacts. The engine seems to play up worse when the cabin is hot, such that after having been parked in the sun it played up tremendously, defaulting to limp home mode within 20 mins. I got fault codes for mass flow meter and 22 which is fuel pump pressure. The strange thing is that in limp home mode it works faultlessly up to the 2000rpm limit. The limp home mode rectifies itself, especially after a long stretch on overrun, like downhill. This makes me think the misfire is a momentary ignition cut out as the ECU goes to rev limit and then rectifies itself, in doing so dumping un burnt fuel into the exhaust. On placing a 2.2kOhm resistor in the temp sensor plug the engine runs faultlessly, though with some pinking under heavy throttle. I still have to check the lambda sensor but am beginning to suspect the ECU. AJH >I still have to check the lambda sensor but am beginning to suspect >the ECU. As a follow up I substituted the air flow meter with one from a subaru. This clears the erratic running but the mixture is out. So I think the fault is in the air flow meter, as the obd1 code suggested, and the erratic engine behaviour is triggered by the engine management system recognising the fault and cutting the engine momentarily. AJH ..and got a code 12.. - its a lottery machine, dont trus ..the connectors to make sure they have good contacts - also cleaned ECU/TCU contacts - have u already checked the cam pos signal from distributor ..worse when the cabin is hot, - cool the ECU with freezer spray, test (from electronics shop ..The strange thing is that in limp home mode it works faultlessly up to t.. - life is like thi The limp home mode rectifies itself, especially after a long stretch.. - whatever bad connection/faulty component - intermittently it comes alive On placing a 2.2kOhm resistor in the temp sensor plug the engine runs faultlessly.. - runs in open loop = w/o O2 sensor. If bad O2 +and+ cam pos signal --->limp mod ..pinking under heavy throttle - dirty engine, plus KS doesnt work or whateve -- Wiikinki www.cardomain.com/ride/748507/ VG30E hasnt got variable cams. VE30DE has hydraulics adj... (gets few hp more and lots problems.) If u have distributor, your engine is VG KS: I dont think so, but actually there is no reference in the Nissan Service Manual After clic clic on the mentioned CDomain 'Favorite Links' read EF & EC 11 and 143. This tells howto measure the cam pos signal with dmm. (My quess is bad gnd in all old VGE distributors... see CDomain p.10 Electronics Cleaner spray is must in solving electronics problems.. http://www.cardomain.com/ride/748507/ http://memimage.cardomain.net/member_images/4/web/748000-748999/748507_217.jp -- Wiikinki www.cardomain.com/ride/748507/ I havent ever seen the check light to be triggered, so dunno. The OBDI -system is stupido.. The safe mode is triggered at least by faulty MAF, CamPos, on certain conditions A/T (sudden brake etc). Lasts until next startup and/or when problem fixed. This info is hidden intothe manual, I am not aware of a list O2 signal can be checked with multimeter, 0-1V signal up/down.. It pay$ to dive inside into those links :) have fu ..use e-mai -- Wiikinki www.cardomain.com/ride/748507/ |
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