XL2007

Thanks for the PDF diagram. I didn't see anything visually wrong with the trunk wiring, so that's been ruled out. I noticed that leaving the battery disconnected for more than thirty minutes will slowly reset not only the TRAC, but also the idle situation. A day after disconnecting the battery, the idle returned to normal, then edged up to a high 750-800rpm in Drive, and 1000rpm in Park/Neutral. It stayed like this for a couple of days, until I needed to turn on the heater (cold snap :D ). I'm not sure if that's related or not, but the idle slowly fell until it hit 250-300rpm. When I got back in the driveway, it just died out. I saw other posts pointing to the ECU as a possible culprit, among other things. What I will do is find another Throttle Positioning Sensor from another LS400 with TRAC and see if the symptoms continue.

This is the problem I'm having out of my 92 LS400. At first the problem seemed to go away with by replacing a bad battery, but it came back days later. The alternator was ruled out as a problem area. I don't have white smoke on startup, ruling out the PS leak problem, but the car simply either refuses to idle or will idle at 300-400 rpm, then die out after a few minutes. As for the idle air control valve everyone keeps talking about, I have no idea where that is and the picture guides people keep sending me are either for the wrong car or just don't point to anything.

Glad you found the solution to your problem. This was an interesting read! :) It's not over. I ran to the grocery store last night. On the way back, all of the symptoms came back -- the refusal to idle, and the super low (350-400rpm) idle on the off-chance that it does. I'll get a new TPS AND check the trunk lid wiring. If that doesn't help, I'm just gonna send the darned thing to the shop so it gets sorted out (even though that'll cost $$$$$ ).

Turns out a bad battery was the culprit. So I had it replaced under warranty and everything's pretty much back to normal.

HERE'S A BIT OF AN UPDATE: So I got back to messing around with the car, making sure that I've looked over everything else before tackling the IACV. So I rechecked and readjusted the TPS and check the throttle cables and other little bits. At this point, the car hasn't moved beyond 15 feet since the problem arose, so I decided to take it around the block once traffic cleared up enough. Two-footed driving came in handy :/ I get back in the driveway and put it back in park.........and it now IDLES. Problem is, it's idling at about 350 rpm and getting lower as time lapses. So I go back and readjust the TPS, only for the car to give out, again. I get back in and start it up..... .....and the battery's stone dead. I get it jumped off (which apparently didn't take much) and restart the car. It fires up beautifully and holds an idle at about 650-700 rpm. The next day, the car was a bit sluggish firing up. Apparently the alternator's charging it just fine, as I haven't had that problem again, just when it sits up overnight. At some point, I'll take the battery to an auto place to have checked out...or if I need a replacement. Pretty weird how the initial problem ended up "going away" like that. I might have to look into that trunk wire ground situation as highlighted in a few other threads, just in case.

I forgot to add that I found what apparently looks like TWO TPS sensors on the throttle body. Maybe because it's a TRAC model, but it looked plenty different than the pictorial guides I have. Now TRAC (which hasn't been working previously) stays on consistently. I've been out of town this week and hadn't been able to work on the car as much as I wanted to. I'm going to double-check the TPS, just on a hunch, perhaps even get a new one and see how that works. I don't see any blue smoke or anything else that might indicate a PS fluid leak or the IACV sucking in said fluid.

I managed to clean the throttle body today. And man, was it just gunked up! But it still didn't fix the problem. Also, the TPS seems to be in good order, as I can adjust the idle revs....when I'm holding the throttle cable so that the car doesn't stall out. I saw the step-by-step guide for the ES/RX concerning the idle air control valve, but I can't translate that to the LS400. If I can just find where that is, that'd be appreciated. I read in another thread that it was under the power steering pump, but that just doesn't sound right -- it has to be around the throttle body/intake or at least the air filter area, right?

Seems simple, but when I looked online for one from the usual auto parts stores..... http://shop.advanceautoparts.com/ProductDe...506&PTSet=A $985?????? This much for what seems like a simple part?

The weather around my neck of the woods' been crazy these past few days -- raining and bitterly cold -- something you really wouldn't expect a lot of in the deep south. Hopefully the weather will let up enough this coming week so I can get some work done! Thanks for all of the advice B)

Thanks. I'll start looking at the IACV and track down any split/worn vacuum hoses asap. And now it seems I've lost the owner's manual, which I need to look up the interior fuse box schemata. Anyone have an online version that could help?

I removed the EFI fuse and relay in an effort to isolate the problem. Without both, it's not getting any fuel at all. Reinstalled, it gets fuel.....as long as you have your foot on the gas pedal. Otherwise, it won't receive fuel on it's own.

This car has a LOT of miles on it. 350k.....at least until the odometer broke. :o To my knowledge, there is no record of the fuel filter being changed. I'll double-check just to make sure and if not, I may just go ahead and have it changed out. Acceleration is no problem. The only trouble is keeping it at idle -- when my foot is taken off the gas, the car simply quits. I have to keep my foot on the pedal to keep it running. I've checked the fuel injection and MAF sensor. I don't see any problems, but I'll double-check when the weather isn't so inhospitable. The spark plugs and wires were changed several months ago (OEM spec if I recall...) and the oil and oil filter were changed just 3-4 months ago. One more thing: the transmission goes in and out of R and D with a SLAM above 1000 RPM. It's probably not related to the problem at hand and can probably be taken care of with new fluid or a flush.

I browsed a few threads with somewhat similar problems, but none of them really fit the bill. My car basically stalls out coming to a light. I doubt it's related to the trunk wiring -- and if it helps, I topped the car off with a full tank last night. I hope it's not bad fuel causing the problem.

Problem surfaced on the way home. I stopped at a red light only to see the RPMs fall to ZERO. Had to pop it in N and restart it, but now it won't idle on it's own -- I have to keep my foot on the accelerator to keep the RPMs up. At this point, I have no clue as to what could make a car that was idling just fine to suddenly stall if you don't keep giving it gas.

Hose down one of your rear wheels with water, then find a hard corner to charge into so you can see if the TRAC is kicking in.