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94 Ls400 Stutter At Idle In Drive


ringtaill
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I've been driving my 94 LS400 for about 6 months now and have been experiencing shuddering when cruising. If I accelerate or let off the glass it stops. Also I have noticed that when I accelerate my heater blower will increase and my wipers will work better. I'm thinking its the alternator. I know that the PS pump sometimes leaks onto alternator, and plan to rebuild the pump. Can I get parts to rebuild the alternator or should just buy a rebuild. I'm pretty good at this stuff and think I could do it if I can get the parts.

I have fixed the steering wheel problem and the drivers side front seat recline problems already.

Just so you know, I've checked both coils and just replaced the battery. There are no troubles on the computer.

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Hi James. People have different terminology for things and so 'shudder' may mean something different to you than it means to me. Shuddering to me is more of a constant misfire feel. I am not sure that the charging voltage issue is related but could be.

So if you are driving at a steady speed down the road, you get this shuddering but at no other times? Is there a particular speed where it is better or worse? Can you try reducing all loads on the alternator while it is doing the shuddering? Turn the heat off so the blowing is not on, turn headlights off in the daytime, defroster off, etc. and see if there is any change in behavior.

You will definitely need to get a voltmeter on that battery to see how it is charging.

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I haven't tried a volt meter on it its kinda cold right now. It's kinda weird on highway speeds with the cruise on it doesn't happen. Looking at 65 to 80 mph . But driving to and from work city driving doing 35 to 40 when cruising just touching the gas to maintain speed it str arts to shutter like it's not getting enough fuel. I'll let off the gas and it will be OK or accelerate and no problem. Some times when coming to a stop a a red light stall, but just have to put in n and start and will run fine for a couple of miles of for the rest of the trip, another 10 miles.

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The symptoms you describe are starting to sound familiar but I would have to do a search. Off the top of my head, the throttle position sensor or pedal position sensor (since it works on cruise) are suspects. Also, it seams to me that the computer capacitors are a distinct probability but I will have to do some more searching. Gotta head off to work right now.

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You know, I rescind that comment about the pedal position sensor as I do not think the "drive by wire" stuff was introduced until the 98-00 models. Still, a crusty, dirty throttle body might behave badly for you. Ever clean that throttle body butterfly plate?

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Hi,

I am having the same problem all of a sudden this morning. I have a 95 LS400 w/ 98K, Had a surging idle, running rough, & the traction control light is blinking. Threatens to stall when I stop. I had a 91 LS before this one that had the same problem, I brought it to Lexus and they ran codes on it & said it was sensors, wouldn't say which ones. Quoted me big $ which I didn't have at the time so I took it home. Stopped on the way home & put Mobil gas in it and it started running fine for awhile, Had been using shell. Did some research on this forum & someone said it might be the Idle control valve or another valve, don't remember the name but I was able to buy them used & refurbished on ebay. Never needed to put them in though as it ran fine as long as I used Mobil gas. I put Shell in once after that because I could'nt find a Mobil and started having the same problem so I figured it had something to do w/ the gas. I have had this one for almost 4 yrs w/ no problems except for a small seep in the power steering rack, which I just keep an eye on. That's why I was so surprised today that I had this problem again. It ties in somehow to the traction control too. The car had 54K when I bought it so I figure it may need a tune up. Probably never had one yet, so I will have to take it in if this doesn't go away.

If anyone figures this out I would appreciate a clue. I put some heet in it & drove it for awhile. We'll see if it helps.

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have you ever considered the air intake between the engine and the air flow sensor (official name escapes me)... if you have a crack in the air flow pipe then when stopping or pulling away it can let air in which bypasses the airflow sensor. Too much air will cause the engine to judder or stop.

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I've been driving my 94 LS400 for about 6 months now and have been experiencing shuddering when cruising. If I accelerate or let off the glass it stops. Also I have noticed that when I accelerate my heater blower will increase and my wipers will work better. I'm thinking its the alternator. I know that the PS pump sometimes leaks onto alternator, and plan to rebuild the pump. Can I get parts to rebuild the alternator or should just buy a rebuild. I'm pretty good at this stuff and think I could do it if I can get the parts.

I have fixed the steering wheel problem and the drivers side front seat recline problems already.

Just so you know, I've checked both coils and just replaced the battery. There are no troubles on the computer.

Heater blower increase in motion is normal, it's a way of Lexus to quite things down at rest, same with the wipers.

I think I had a very similar problem before. Wasn't serious enough to stall the engine or had to put it in neutral. I would get "hiccups" from the engine. It only happened when cruising (maintaining speed with no acceleration or foot off pedal) around 30-45mph. It was subtle and erratic and bothered the heck out of me. Engine was strong with acceleration and fluids in transmission and differential were checked. However, I decided to check my spark plugs, perhaps there was a cylinder not firing right. When I pulled the plug, it had those Bosch 4 electrode plugs! I had a suspicion that with those gimmicky plugs, the coil voltage is not reliably arcing. I replaced them with the OEM NGK single electrode iridiums and the "hiccups" went away! If I were you, check spark plugs, plug wires and distributer rotors, or at least the service history. Rotors are only good for so many miles. Perhaps an ignition tune-up should be in order soon?

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  • 1 month later...

have you ever considered the air intake between the engine and the air flow sensor (official name escapes me)... if you have a crack in the air flow pipe then when stopping or pulling away it can let air in which bypasses the airflow sensor. Too much air will cause the engine to judder or stop.

It doesn't happen when accelerating or slowing down only when cruising with my foot lightly on the accelerator

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