BACKFIRE Posted June 14, 2008 Share Posted June 14, 2008 2 mounths i bought a 90 LS400. Ran grate but neaded a water pump. I replacer the water pump, front brake pads and roters, thermostat, and change oil. I`v been working in it slowley when i get free time. After geting every thing done the car i started it and it will run fine for about 3-5 min but after that it revs up and down at idel and the Check Engine light came on. I got a code 31 (air flow sensor). So i ordered a used sensor, insteled it and does the same thing. So then i went to O`Rielly`s and got a new sensor and still wont run. So i went down the street from me to a friend that has a 1991 LS400 and tryed my original flow sensor on his car and it runs fine as does the other sensors i got. So my question is what els could be rong with my car???? I keep geting a code 31 (air flow sensor). Could it be a ECM problem??????? Quote Link to comment Share on other sites More sharing options...
Bali26 Posted June 15, 2008 Share Posted June 15, 2008 Could be the wires to ECM. Try disconnecting battery. You might have messed something up when u replaced the water pump... Quote Link to comment Share on other sites More sharing options...
BACKFIRE Posted June 16, 2008 Author Share Posted June 16, 2008 I let it sit for a week with the battery off and it still does the same thing. I,m about to take it to the dealer and droop some big money on it. I hate to but it looks like need to. Quote Link to comment Share on other sites More sharing options...
eatingupblacktop Posted June 16, 2008 Share Posted June 16, 2008 Three items come to mind ... idle control valve, vaccum leak, coolant temp sensor. Quote Link to comment Share on other sites More sharing options...
BACKFIRE Posted June 16, 2008 Author Share Posted June 16, 2008 Thank you E.U.B.T.. I totaley forgot about the idle valve. I checked it and the plug was off!!!! The little clip that holds the plug on is broke. I put a zip tie to hold it on and IT RUNS NOW!!!!!! Thank god the valve was not bad. A new one cost $900 I Quote Link to comment Share on other sites More sharing options...
eatingupblacktop Posted June 16, 2008 Share Posted June 16, 2008 Nice to dodge a bullet every so often. Those zip ties come in real handy just about everywhere. Can't think what would we do without them. Quote Link to comment Share on other sites More sharing options...
BACKFIRE Posted June 18, 2008 Author Share Posted June 18, 2008 Zip Ties, Papper Clips, and Duck Tape will save the world one day. :P Quote Link to comment Share on other sites More sharing options...
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