Check Engine Light

[LS 0181158]

I recently purchased a 1993 LS 400 with 204K miles. The car usually drives fine--when it does it is actually the quietest, smoothest, most solid car I've ever driven. One would think the car doesn't even have 100K given how well it normally drives. There are no warning lights when it drives this way.

However, since the beginning, there has been an issue with the check engine light illuminating and the revs fluctuating violently as the light flickers on and off. The car naturally loses power as well. When this is happening, taking your foot off the gas (especially at low speeds) will result in stalling. The car will restart, but it sometimes must crank for a few seconds, and the engine will stall immediately unless you keep your foot on the gas to "catch" the revs when the engine fires. Mind, this problem only happened occasionally, and letting the car sit would usually make it go away.

I took the car to a Lindsay Lexus in Alexandria, VA, and they charged me $111 to tell me that the problem related to the mass air flow sensor--a $1,100 part according to them. I ordered the part (with a 90-day warranty) from a junkyard for $165 and installed it. I disconnected the battery and pulled the EFI fuse as well. Following this, the car idled smoothly for 15 minutes with no check engine light, and then it cut off.

I've since found that several hose clamps on the air passageway to the engine were loose. That once again cured the problem only temporarily. Last night I replaced the air filter, which was pretty dirty. So far the car has run fine, except for a less-than-1-minute period on the highway at 70 mph when the issue reoccured, then went away.

I'm all out of moves here--can anyone think of other things to check? I feel like it's got to be another sensor somewhere, the way the problem comes and goes randomly, with no apparent "trigger".

Thanks in advance for your thoughts.

[alsalih]

From my experience when a vehicle dies as you described and then will work after you let it sit, this is usually related to a faulty fuel pump or one that is going out. This difficult to diagnose because as you describe it's intermittent, however it will get progressively more common.

[sha4000]

sounds like you just need a tuneup. when your car acts like it wants to stall out either your not getting [proper spark fuel or air 9 times out of ten.b4i change the pump i wuld definitely change the fuel filter, especially at that mileage. the filter is probably a little clogged

[obergc]

You didn't say if you are still getting a check engine light. If you are, there must

be a fault code stored. Get the fault code and go from there.

[LS 0181158]

OK, so--fuel filter (I was already thinking about that), tune up, and then possible fuel pump. Would a clogged fuel filter actually cause the car not to idle--to actually cut off, or idle erratically? When I try to rev the engine up to keep it running, it'll rev smoothly, but the tach needle will rapidly and relentlessly "dive" toward 0000 rpm before zooming smoothly back up in keeping with where my right foot is (this of course is only when the check engine light is flickering on and off).

Also, the engine has recently been more smooth if the light is on, but acceleration is painfully slow because there is very little power and the transmission starts out in 3rd gear (I usually shift it manually 1st, 2nd, etc when this happens). Pressing the gas more than 1/3 way down will cause the fluctuation and bogging down, but the engine is smooth while only feathering the throttle. Driven in this way I have been able to cruise at 75 mph. However, the engine feels like it's running either to rich or too lean.

I'm super confused how the car can drive with NO PROBLEMS for one or two days (sometimes over distances of 200-300 miles), being parked, restarted, driven, etc.--no issues. And then all of a sudden, the problem returns. It does not seem to be dependent upon temperature, moisture or any other atmospheric factors. Can a clogged fuel filter be great for several days and then cause these massive problems?

The check engine light will go away on its own when the car decides to "act right". Last night, it came and went within a minute, all at 70 mph.

Do you all think I should take it back to the dealership and demand another diagnostic, this time for free? I can't pay $111 for them just to stick a plug into my engine compartment and read the code. Also, I was chagrined that the first time they did not notice any of the loose clamps on the hoses and try to trace the problem to a simple source, instead quoting me a $1,300 repair.

Anyways, thanks for those speedy responses--this a really a great forum!

[SKperformance]

Go back and ask them why they did not catch the simple things for a diagnostic fee which you paid for?

Then ask for a free check but by a technition not the mechanic caliber that did it the last time.

[sha4000]

Go back and ask them why they did not catch the simple things for a diagnostic fee which you paid for?

Then ask for a free check but by a technition not the mechanic caliber that did it the last time.

←

+1 i agree with sk since you paid for a service that was performed inadequetely

[LS 0181158]

OK, I will do that. Others I know have recommended I do the same thing, so I feel even more vindicated now. Hopefully this dealership will deliver the "customer service" Lexus is known for when I request a free diagnostic and point out their poor attention to detail the first time.

[LS 0181158]

Going to the Lexus dealership tomorrow. Tonight I drove the car, and the check light DID finally come on and the car ran with reduced power. However (I guess because of the new air filter having something to do with it) it does not cut off anymore, nor does the engine run rough anymore--it simply cannot be revved up very high and has greatly reduced power. Still, I can get up to 75 mph pretty easily.

ALSO, I noticed that when the light is on, the car blows distinctly black smoke and burns through gas at an alarming rate. It does not do this under normal conditions (without the light). I believe this means the car is running rich (too much gas)??

I will see what the dealer says tomorrow. Thanx again for your inputs.

[et1957]

i believe the filter can be the trouble also,,just to compare i had a tractor lawn mower with the same trouble,,worked for a while,then would shut off by itself,,and not turn back on for days,,it would work fine again,,then just stop running again,,,,the reason the trouble took so long in my case to resolve was a faulty ignition as well,,which i changed first since i was having starting issues on top of not staying on,,, before it was all said and done, i changed battery,ignition,,,,,and finally got the fuel filter changed and havent had trouble since,,,,,good luck,,

[91L3xus]

Check the hoses that connect to the throttle body and the air box; I had similar problems and I tightened the clamp to fix it.

On a side note, my ES250 will be going in to Lindsay for a $750 transmission and dogbone mount replacement tomorrow. If you happen to see the crappiest Lexus on the lot, let me know...lol. <_<

Good luck, as I hope I'm getting what I pay for, as well as you.

[SRK]

It is generally accepted that a flickering tachometer, one that seems to be disconnected from the actual RPM of the engine, shows a fault in the ignition system. Think of those things that will NOT cause a tach to flicker - fuel pumps, fuel filters, MAF sensors, and so on. It may very well be one of the ignition coils or one of the primary circuit components in the ignition system. That's what will cause a tach fluctuation. It might even be a bad ground path.

[914lps]

I would go with SK's advice. Let us know what the dealer tells you. I would also ask as you bought a used Mass Air Flow ... Did you clean it before you put it in?

It takes only a few minuts to get it off to clean it and a few bucks worth of spray cleaner. I would also disconect the battery for 5 to 10 min, after cleaning it or just disconetc before cleaning. This will resety the computer. Can't hurt.

[LS 0181158]

Good advice all!

91L3xus, I may have seen your car this morning (Dec. 8). Is it black in color, missing several center wheel caps? Didn't look THAT bad :-). It was the only ES 250 I saw, and I was there from about 9 to 11:45 AM. I think that car had a gray interior, not a tan one, so maybe it wasn't yours. What were you getting done to your transmission again?

914lps, I have disconnected the battery any time I did anything under the hood related to this problem (including MAF replacement). However, I did NOT clean the MAF before I put it in. Here's why; I tried to clean my original MAF. However, when I took out the three screws, disconnected the plug and pulled it out, I could not see any "little wires" like I have read I will see. There's just a 2-3" plastic piece that sticks down inside the metal box. I sprayed fast-drying contact cleaner on that piece anyway, but when I reinstalled, the car would not even run with my foot ON THE GAS. I was later able to drive it a little bit (around the block), but overall driveablility was not restored until I received the new junkyard MAF in the mail and installed it.

And SRK, tachometer always seems to correspond with the actual RPMs--including unruly idle fluctuation.

Upon my inquiry, the dealer said they would not charge me for any further diagnosis, stating that my initial $111 would cover any other investigation until they actually began work on the car. As I noted above, they had my car for nearly three hours, and finally returned to tell me that although I drove the car there with the check engine light on, the computer was not throwing any codes at all. Because of this as well as the randomness of the problem with no apparent trigger, the tech believes that the ECU computer itself is basically shot. He was willing to test by swapping in an ECU from a "certified" car, but said it would take another six hours or so before the part was available to him. I couldn't wait any longer, and he assured me that he was pretty sure the ECU was the problem. He said he did "check the inputs and outputs" of my ECU, but really didn't have any other clues. He also stated the car is indeed running "very rich" when the light is on (which must be why gas disappears so rapidly while this is going on and my back bumper is BLACK around the tailpipes).

Since 11:45 this morning, I have driven my car off and on all day until now (10:00 PM), with absolutely no problems. I am keeping my fingers and all my toes crossed, but experience up to this point suggests the issue will probably return.

I'm wondering how much sense this guy's conclusion makes--or do I really just need a fuel filter or, at most, a tuneup. Remember, there are now apparently no trouble codes when the check engine light is on.

[SKperformance]

If you have black smoke coming out and increased gas usage then i would point at a

ignitor or rotor and cap

spark plug wire

fuel injector.

I think the fuel filter is out as it is getting gas just too much which a filter cannot do.

You have a combustion issue point to incomplete burn.

[sha4000]

yeah if your running rich i would doubt the fuel filter at this point also.could very well be that the ecu is throwing out incorrect signals

[LS 0181158]

SK, prior to having this car, I drove a 1990 BMW 535i for about 46K miles. When I had a tuneup done at 165K miles, the spark plugs, spark plug wires, and distributor cap and rotor were all replaced. So barring a bad ECU, it seems like a tuneup will likely cure any other causes of the problem. The car still hasn't acted up since the Lexus dealer had it yesterday morning, though.

[92ls forhundo]

hello i was wondering if this problem was ever solved? from reading the about the problem a flag went up in my grey matter that, perhaps o2 sensors and/or cats?