93 Ls400 No Throttle Response, Running Rough, Rumbling, After Rain

[Mikes515]

I noticed about a week ago that when i started the car in the rain is was a little rough. I Took off from my apartment and the throttle lacked response for a second then we continued on our merry way, so i dismissed the issue. Tonight at 1030 after the big hurrican cleared decided the store was neccesary for drinks. Started the car, it ran rough, sounded like a pump was having an issue (not sure which one), after letting it sit for about a minute took off down the road and there was barely any response at times to hitting the gas, also it felt as if the engine was going to blow up. It rumbled like a roller coaster, and pushing the throttle after letting it coast for a bit just seemed to make it worse. Turned right around and got it home, let it idle and it was still rough. Quite irritated at the moment, and Wondering what this could possibly be. On normal dry, cold, even warm or hot days it does not do this. Any help, is much appreciated as the anger level is rising by the minute!

[SRK]

Sounds like the common failure of one of the two ignition coils. Check the primary circuit of each with an ohmmeter and compare. Or snap a timing light if you have one, on the high tension lead of both, and the one that isn't triggering the light is the bad coil.

Your car has enough mileage that it's a distinct possibility - although it's still important to diagnose it.

[Mikes515]

hmmm alright. How about plugs and wires as well? It only seems to do it when extremely damp or wet outside. After it warms up and gets up to temp it drives fine.

[SRK]

It won't be spark plugs, and if it's a wire it would be one, and that wouldn't cause the lack of power you are noticing. However pull all the plug wire covers off and have a look. Look at the spark plug connectors and see if there is any carbon tracking. And ohm check the two coils.

[landar]

Mike, on a 93 LS, you have two distributors with caps/rotors, two ignition coils, and plug wires. As you suspect, the insulation on these components can start to break down especially in high humidity weather. What I do is take an empty spray bottle, such as Windex, etc, and fill it with distilled water. Then I spray a mist on the coils and wires with the engine running to see if I can get the break down to occur. Do it in a darkened garage or at night and you can actually see the spark-over occurring. That test will help you pinpoint if you have an insulation breakdown due to moisture. If not, you can look elsewhere.

[Mikes515]

Alright, thanks for all the info and ideas, Will be updating once figured out. Most likely within a couple days! thanks a lot!

[steve2006]

Another symptom is the cats glowing red when the engine has been running for a while due to unburnt gas entering them and this can damage them so don't leave the job too long.

The driver's side is the usual culprit and the hardest to replace.

The link below may help.

http://us.lexusowner...ls-on-92-ls400/

[Mikes515]

well, plugs and wires done, rotors, even a bushing in the rear, few minor other things. Seems to be doing quite nice now :). Thinking its all set for the time being. With the miles im sure theres more that could be done. Thanks for all the info and input.

[freegard]

Looks like we have the same paint and car. (199 Alpine Silver) I am looking for an exterior driver door handle and where on earth can I get a new set of these rims we both have. None of the aftermarket rims compliment the car like these and having them rechromed is untenable for several reasons.

I changed out all the ten suspect electrolytic polarized capicitors with mil spec 115 F. caps and instrument cluster works. Okay that was chit chat....

Reason I am posting this here:

The car will not tolerate hard acceleration; it dies as if it is governed at 2000RPM; if I gradually accelerate it is smooth and runs great. It is a new thing that began after I filled up the tank. I do not know if bad gas can cause that. I do know my temp sensor has needed replacing but I also think I may remove the ECU and replace the few caps in there too. Might do it when I wake up in the morning. A great alphatronics electronics store nearby.

I am apprehensive:

I have been looking for a tutorial for removing the ECU from the 1994 LS400 but all I can find are vague instructions: Remove the panel under glove box (okay exactly how?) then pull back the carpet and remove the ECU. Those instructions don't inspire me. The car is not accelerating, this thread is marginally relative. I realise this however,

I have spent an hour browsing for something germane but nothing I found precisely reflects the acceleration issue I am having and so here I am.

I think it that it is definitely compounded by the ECU and the temp sensor. Since I can do the work on both and spend less than $35. doing it this is where I will start. Any helpful comments will sure be appreciated and explored.

[Mikes515]

Hey Freegard, As for the ECU stuff im not quite sure about that stuff. Rims though, unless you've got the budget to do it, the stock rims in chrome are around $295 each. Im sure there are a few that are cheaper but most likely not by much. There are even some that are more expensive. Really depends on what your looking for though. If you have to have them and have them chrome then thats the downer. I'm bummin since ive gotten my lexus because I had put rims on my old eagle vision TSI but was un able to keep them when the car decided to die at 56k miles. They were black spokes with chrome lip. But thats an attained taste not everyone is into the custom rims. I hope this is of some help! Also for your handle, there are multiple sites that sell them. Could try ebay or the dreaded junk yard as well.

[faberchris]

Glad I found this. My check engine and VSC warning lights came on yesterday and I started having an issue with loosing acceleration. It ran fine for a few miles and then lost all acceleration, just basically idling. If I push the pedal all the way to the floor, I can get a little bit out of it, but that's it. I turned it off for a few minutes and restarted. The warning lights stayed on but it ran normal for a few miles and then the problem started again. It smelled like something was really hot or burning. I looked under the hood but didn't crawl under the car. I'll check the coils, hopefully that's my problem.

To respond to Freegard - if you're looking for about removing the ECU, try searching for removing the A/C evaporator. You have to pull out the glovebox and everything, and the ECU is right there. I found some step by step instructions for evaporator removal on my car and the ECU was part of that process. The ECU itself is just a couple screws and a bunch of wiring harnesses once you get to it. Here's a start: http://www.clublexus.com/forums/ls400/287083-how-to-replace-ac-evaporator-and-blower.html#post2683620

[Mikes515]

Faber, i believe coils will most likely be your issue. I was informed that if it was coils then usually it is an ongoing problem. Replacing the wires and such for my car seemed to do it. It was only having issues in wet, and humid weather. Best of luck!

[landar]

Glad I found this. My check engine and VSC warning lights came on yesterday and I started having an issue with loosing acceleration. It ran fine for a few miles and then lost all acceleration, just basically idling. If I push the pedal all the way to the floor, I can get a little bit out of it, but that's it. I turned it off for a few minutes and restarted. The warning lights stayed on but it ran normal for a few miles and then the problem started again. It smelled like something was really hot or burning. I looked under the hood but didn't crawl under the car. I'll check the coils, hopefully that's my problem.

If you have a 98, you have Coil On Plug technology, not like the pre-98 models. There is a coil on top of each plug so that is likely not your problem. I would hook up an OBDII scanner and read the code(s).

[landar]

Freegard, I do not know if the tank fill-up was just coincidence or not but you *might* consider replacing the fuel filter as perhaps accumulated dirt from over the years (or with that fill-up got dislodged) is restricting flow. Or perhaps the fuel pump is losing volume flow due to age? The filter is a fairly easy change.

[faberchris]

I realized that I have a different coil setup on my 98. They coil on plugs seem to be much more expensive than the previous technology too. I can test them, that should be easy enough but I'm going to get it to a code scanner too.

[curiousB]

As Landar suggested this isn't likely a CoP issue (coil over plug). Its unimaginable that several CoP units failed simultaneously so it must be something else.

Start with the obvious stuff. Get some aerosol contact cleaner and remove connectors to a few sensors and spray them with cleaner and reassemble. Connectors like, MAF, Throttle position sensor, crankshaft position sensor, ...). If any of these are intermittent you'll have problems. You really need to do an OBD-II code dump as well. There are probably good clues in the DTCs in the ECU.

[Mattmans94]

Gents,

I have a 94 LS 400 that I replaced the alternator on, due to the air controll values, religious ways of leaking ATF from the PSP, which eventually shorted the electical connections from Alt to Bat.

That was fixed, but now, 2 weeks later, the car starts this mis firing, and seems to be off, idle wise, as to the tune of 200-300 RPMs, and I feel also, that I have to floor it to get the gett up out of the darn engine.

Being a 94, any suggestions to a new, but very experienced mech, of this Lexus issue??

[landar]

The first thing I would do, Matt, is to check for any codes. Could be a variety of things and may not be related to the Alt change-out.

http://www.lexls.com/tutorials/intro/codereading.html

Wecome!