hpicazo_link Posted June 12, 2008 Share Posted June 12, 2008 I have a big problem with my car. It's a 1990 LS400. The problem is huge because it's been wasting double the gas. I don't really know why. We have the Air Flow Mass Sensor plug disconnected (I don't know if that might be why it wastes the gas). We disconnected the plug because when we connect it, for some reason the car accelerates a lot, it makes the RPM go up to about 2 when it's parked. If anyone has had this problem or know something, please help! I don't know much about cars so please try to explain as detailed as possible. Or however. I can explain your response to a mechanic and I'm sure they'll know. I just need some information on what it might be. Thank you. Quote Link to comment Share on other sites More sharing options...
raymsixsix Posted June 12, 2008 Share Posted June 12, 2008 Welcome to the LOC, hpicazo! I'm sure one of the gear heads will be able to give you some advice. Smooth1 would be a great member to ask as he's very knowledgable about engines. Good luck. Quote Link to comment Share on other sites More sharing options...
nc211 Posted June 12, 2008 Share Posted June 12, 2008 you need the MAF sensor working, otherwise the balance between air and fuel will be off, a lot. That is your problem. It sounds like you might need a new one. It's not a difficult repair. But without it's input into the engine's operation, it's going to supply more fuel into the engine than is normally required, because it can't figure out how much air is going into the intake chamber. It's running rich..way rich. Quote Link to comment Share on other sites More sharing options...
eatingupblacktop Posted June 12, 2008 Share Posted June 12, 2008 You'll also burn out your cats. Not cheap! Welcome to the club. Quote Link to comment Share on other sites More sharing options...
TA in KC Posted June 13, 2008 Share Posted June 13, 2008 Here are some links for a replacement MAF sensor. They are very easy to install yourself. http://cgi.ebay.com/ebaymotors/LEXUS-LS400...5QQcmdZViewItem http://cgi.ebay.com/ebaymotors/LEXUS-LS400...5QQcmdZViewItem Quote Link to comment Share on other sites More sharing options...
914lps Posted June 13, 2008 Share Posted June 13, 2008 If you replace the MAF and still get the wild idel swing, then look at the idel control valve. Do a search to find out how to test it. Quote Link to comment Share on other sites More sharing options...
smooth1 Posted June 13, 2008 Share Posted June 13, 2008 You actually have two problems here. The first one is the idle issue. You either have some bad vacuume hoses, either leaking or not connected, or the Electronic Throttle Control System (ETCS) which controls the engine idling speed. The ETCS operates the idle control valve, and adjusts the intake air amount to obtain the targeted or programmed idling speed which is controlled by the ECU. It also retards the ignition timing and the ETCS opens the intake air to help warm the catalists during cold start ups. Which is why the car is idling too high when you connect the MAF. And the second problem you now have is the disconnected MAF, which also contains the IAT sensor. Intake Air thermostat. Which tells the car what the temp of the intake air is. With out the IAT, and MAF, the car is put into a type of protection mode and has retarded the timing and running rich as the temp sensor is in a default mode. You will have to reconnect the MAF and fix the thottle issue seperately. Quote Link to comment Share on other sites More sharing options...
hpicazo_link Posted June 14, 2008 Author Share Posted June 14, 2008 You actually have two problems here. The first one is the idle issue. You either have some bad vacuume hoses, either leaking or not connected, or the Electronic Throttle Control System (ETCS) which controls the engine idling speed. The ETCS operates the idle control valve, and adjusts the intake air amount to obtain the targeted or programmed idling speed which is controlled by the ECU. It also retards the ignition timing and the ETCS opens the intake air to help warm the catalists during cold start ups. Which is why the car is idling too high when you connect the MAF. And the second problem you now have is the disconnected MAF, which also contains the IAT sensor. Intake Air thermostat. Which tells the car what the temp of the intake air is. With out the IAT, and MAF, the car is put into a type of protection mode and has retarded the timing and running rich as the temp sensor is in a default mode. You will have to reconnect the MAF and fix the thottle issue seperately. Thank you for your help. So do you think I would have to replace the MAF? Quote Link to comment Share on other sites More sharing options...
hpicazo_link Posted June 14, 2008 Author Share Posted June 14, 2008 You'll also burn out your cats. Not cheap!Welcome to the club. uuummm...what is that?...haha.. Quote Link to comment Share on other sites More sharing options...
hpicazo_link Posted June 14, 2008 Author Share Posted June 14, 2008 Here are some links for a replacement MAF sensor. They are very easy to install yourself.http://cgi.ebay.com/ebaymotors/LEXUS-LS400...5QQcmdZViewItem http://cgi.ebay.com/ebaymotors/LEXUS-LS400...5QQcmdZViewItem thanks Quote Link to comment Share on other sites More sharing options...
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