1996 Lexus LS 400 Car wont start period some days, other ti

1996 LEXUS LS 400
125,000 MILES • V8 • 2WD • AUTOMATIC
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JLOSEKE
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The car sometimes just wont start at all -- the starter turns the engine fine, but it never kicks. That might happen at 7 pm in the evening -- can't start it no matter what you try. Leave it until morning, and it starts perfectly, as though there was never a problem. This has happened 4 times now.

In the last three weeks, it's started having problems after your driving. Everything is fine, starts fine, runs fine, then suddenly it starts hesitating, and it's difficult to get the RPM over 1500. I couldn't get the car over 10 mph going up a hill one evening. You press on the gas, and it almost kills, until you let off, then you get a short kick.

I took it to the local auto shop, and they kept it for 3 days, driving it all over the place, multple times a day -- and couldn't reproduce either problem.

No codes, no check engine light. Zip. That was three days ago. Yesterday, it started hesitating again (in the evening when they're closed). This morning it started fine, so I drove to work (no problems). Try to go home 8 hours later (75 degrees today in St Louis), and it won't start. Engine cranks, but no kick.

Lexus dealer looked at it 4 months ago after the first two events, and were unable to diagnose the problem.

Ideas? This is driving me crazy!
Nov 9, 2010 at 5:38 PM
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No matter what I write, unless it can be confirmed, it is only a suggesion/guess. Intermittants are brutal. Had one for a month and the symptom NEVER happened. Three blocks from the shop it happened to the customer after she picked ...not a happy camper...it happens.

Not sure if this is anything like the 4.0 liter, but might be worth looking at. Carbon buildup on the iac under the throttle body may be the source. Clean both the iac and throttle body and all is well. Carbon buildup may not allow iac to move correctly and maintain the correct position.
Nov 9, 2010 at 6:53 PM
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JLOSEKE
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After the problem I posted last night, I left the car overnight (25 miles from home). This morning when I returned -- it started right up, as though there had never been any issue at all. No delay, no struggle to start -- no problem!

Since the battery was low from the prior days issue, I left it to run for about 45 minutes to recharge the battery some, after which I shut it off (it's in the parking lot at work -- had to work!)

That was about 8 am.

About 2:30 pm I went to start it, planning to drive it home -- NOTHING. Turns over fine, just like before, but no kick.

It's gotta be something related to OUTSIDE temperature. Late in the day or evening is when it won't start, but first thing the next morning it starts perfectly.

This is about 5 times over 5 months this same scenario has played out.

Does that fit with the IAC hypothesis? Or is it likely to be something else?

Also (since I'm not automotively gifted) -- what's an IAC?
Nov 10, 2010 at 5:41 PM
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No one is automotively gifted lol.... Idle Air Control (Motor) And yes I think this is very possible. Carbon will get sticky and can get worse when cold as it is thicker. This is the carbon build up on a throttle body.


https://www.2carpros.com/forum/automotive_pictures/30961_P1190121_2.jpg

It can get very thick and tar like. I have seen it make throtlle body plates stick open. IF you were to press on the accelerator and it stayed open it what I refer to.
Nov 10, 2010 at 6:13 PM
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JLOSEKE
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Just to confirm -- the car STARTS when outside temp is COLDER, and does NOT start when the outside temp is WARMER.

Does that fit with your analysis? I guess I read it as "sticky" (cold) would cause more problems, yet cold is when I have fewer issues.
Nov 10, 2010 at 10:09 PM
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I would still recommend a intake cleaning and/ or pulling off the iac and cleaning it. This is an often overlooked maintenance procedure. Setting that aside, there is another wya you may be able to duplicate this problem to narrow down the source. Using a hair drying, you can heat up components individually and try to re-create the no-start. Don't cook anything just raise the temperature. Focus on ignition components, I would start at the ignitor area first.


https://www.2carpros.com/forum/automotive_pictures/30961_1l_1.jpg


https://www.2carpros.com/forum/automotive_pictures/30961_1l1_1.jpg

The ignition switch is another. I believe they have a transponder in the switch that my not be giving a signal.
Nov 11, 2010 at 5:07 AM
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JMART77
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I have the exact same problem with my 96 LS. Did you ever find a solution?
Nov 24, 2012 at 3:41 PM