My LS has been acting a little strange lately. Seems like once things started heating up down here (we're talking Yuma folks, I see 110-120F for nearly a month straight every day at the high point of summer.) my engine started surging and hesitating, what I would expect form either dirty fuel injectors or a dying fuel pump. ran fuel injector cleaner, did the seafoam treatment, etc. Nada. I notice it all the time now though, and when the tank gets low it's much worse. (I try to keep it halfway full at all times but sometimes you just can't.) When I bought the car, the prev owner said he had just replaced the fuel pump, and since the float sensor appears to be jacked up (goes to half-tank when full and generally sits at E after 100-125 miles.) I believed him.

Shortly after I got this car, my (then) girlfriend decided a car that needs premium would do just fine on Unleaded. other than that moment of brilliance, its always had at least 91 octane, if not higher.

I have had some minor trouble with the main seal (it wants to leak once I get the car warmed up) but otherwise this car has been bulletproof. Before I go tearing into my trunk, is there anything else I should be checking?

 

I hate bumping.

Anybody? The thread has 39 views already.

 

I would attribute surging/hesitating to the intake tract before I would look at fuel delivery issues, esp. considering that fuel system isn't often a culprit on the LS.

I would focus more on the throttle body, MAF sensor, and such.

 

Thank you for that advice akxx...I unhooked my battery, reset the comp. and hooked everything back up and the problem is *almost* non-existent. I'd say that's a good indicator of a dying sensor too.

*sigh* now if I only knew how to check that stuff...

 

UPDATE

Well...the car's almost dead at the moment. Its idling extremely rough, I mean engine-shaking rough, burns rich as all hell and doesn't want to respond to the throttle at ALL...I'm talking 1/4 power or less than expected. I found a small vacuum leak where a plastic connector was broken off inside the littel rubber hose...I can fix that with a little brass nipple or some similar construction, but I really don't think that's all that's causing it. Any ideas before I ahve to drive this thing(really don't want to do that considering how badly its running) to a mechanic?

 

I used to have a Supra and when you unplugged the maf snsr it would do the same thing you described, possibly it is covered in K&N oil? I am almost positive that is what it is, poor idle, rich as hell, and little rrsponse to throttle input

 

It sounds to me like it could be the MAF as well. Is there a check engine light?

 

Check for dead coil! You have two of them.One for each side.

 

Thanks for the input gents; no check engine light at the moment, the guy who was driving the car at the time disconnected the battery to reset everything, having remembered that I had been doing that previously to help with the more minor symptom above. Well, what can I say, mechanically the guy's good but he works on an 87 Bronco2, not these cars. Whatever codes ahd been thrown are gone, and the car hasn't been running or rolling long enough to throw a new one. It ran about a half-hour Sunday in which I putted forwards and back along a long driveway in an effort to throw one, then I drove it a short distance (three blocks or so) to a place where it could be parked for a little while longer than where it was. its still not home, I'm not sure I want to do that to my car.

 

HOLY SWEET MOTHER OF GOD!!

I know it can be found for substantially less, but...518 bucks is an awful lot for a freaking MAF sensor.

Rock auto sells it as an entire unit, aluminum housing and the whole deal. $70 core charge. Can't search Ebay yet as our work computers filter such sites out. Hopefully its just dirty or something.

Also, another source, who is a Lexus dealership tech, says it could be the spark plug wires or dist, so I'll look at those tonight. Good thing I have a multimeter handy...

 

http://car-part.com/cgi-bin/search.c...ey=&userPage=5

Buy one from the local shop. You can return it if MAF is not the problem. But I am sure it it is caused by a bad MAF sensor.

 

wow, great link dashan; thank you. This should be added to a sticky somewhere if it isn't already.

 

OK...my MAF sensor should be arriving via UPS this afternoon, but last night I finally got the time (and it was payday so I got the materials) to tear into the engine a bit. I'm replacing my spark plug wires and plugs, which is good considering they appear to be the ones from '94. The wires I know for a fact are OEM, didn't get to start pulling plugs last nite though.

Seems like the max resistance was 23, five of them were over 40. I had to take one wire back to the store because though brand new, it was showing a resistance of 493.whatever...that was pretty cool.

Also, two of the wires were in such bad shape that though I was being extremely careful to preserve the wires, these two decided to break on me, leaving a length of wire in the hole that I'll have to pull out before I remove the spark plug itself. pretty exciting stuff, huh?

And for a funnier(though odd and somewhatstupid) story...once I hit a stopping point last nite (sundown) I had the wires sitting in thier little chambers, jsut resting onto of the old plugs. Shut the hood, went to turn off the radio...decided to make sure I woul dhave enough juice to turn the engine over once I was done with the job.

Yeah, it turned over all right...and sputtered to life! Pretty damn funny, since neither I nor the neighbor kid were expecting it. There she is (the car) intake pulled apart, wires all over waiting to be routed and secured, crappy old plugs and everything...just rumbling along. (no rear mufflers, when the engine's running rough it sounds like a truck/muscle car with a pretty aggresive cam.)

oh, and rest assured, i killed the engine immediately.

 

There is a new MAS cleaner on the market at auto shops, K&N FILTERS do require oil after cleaning and some times it gets on the MAF sensor all you have to do it try and spary the MAS cleaner on the air sensor to see if this the problem. If it is the MAS there is a company in San Francisco who rebuilds them and will trade your core and about 150.00 exchange. I don't have the name but you could possible look on google for MAS rebuilders.
To clean the MAS sensor just pull out the air filter and spray the MAS cleaner up the tube at the sensor wait about 5 minutes to let it dry I tried this on my MAS sensor and it worked just great since I use K&N filters which by the way helps the Lexus LS400 run better.

 

be very VERY careful as some MAF cleaners have been known to damage the extremely delicate sensor wire.