Lex3486

The last day or two I've been noticin a slight hesitation when my car is accelerating from a full stop; it occurs when the car is still in the first gear, right around the point where it reaches 2500RPM. The engine suddenly hesitates and doesn't want to gain any more rpms, but if you let off the gas slightly, it resumes as normal. The same has also happened right at the instant it shifts to second gear. It doesn't however occur when the car downshifts once underway; that all seems fine. Also, I've noticed it's been shifting slightly rougher, I might say. What I mean is that the rpms will reach the point where the transmission is supposed to shift and then they'll drop down some, as if perhaps it's already shifted, but then after the drop in engine speed, the gears engage, at times with a jerk. One more thing I've noticed is that today I was sitting still idling with the A/C on and I noticed the whole car began to vibrate like the engine was dying, but the rpms were completely normal; right around 750; normal idle speed and without any fluctuation whatsoever; I revved it up and it got a little better and then I revved it again and it went away completely...IS MY CAR DYING OR WHAT????? I've checked the intake piping b/c I know this all seems somewhat indicative of problems there, but it appears to check out alright. No check engine light and all my fluids are at normal levels and don't appear to be any strange colors or odors. I've heard of people replacing the mass airflow sensors before, and I was thinkin this could possibly be my problem, but don't know the symptoms of such a part failing. Any help would be deeply appreciated.

amf1932

I would check the fuel pump pressure. A clogged gas line filter would make the engine starve for fuel while trying to accelerate and also when it's under load.

steviej

iTrader: (1)

my first though would have been similar to yours......air intake ducts. Toyo/Lex engines run like crap when there are even pin ***** size holes in the plastic duct work. I have actually taken the duct work off and put a flashlight inside, cover both ends and look in a complete black room to find the holes. If no problems here, then the next thing I would think of is exactly as Alan has suggested.....fuel delivery problem.

The third area I would look at is the throttle body. Is it in need of a cleaning? MAF sensors are usually good or bad. bad ones trip the CEL. I haven't seen ones "on their way out". Hope it is not the MAF.....$$$$.

What about the air filter, is it occluded or cruddy? If not the air filter, what about the air intake before the filter box. Check here to see if there are any leaves. I'm in New England with a lot of pine needles. They like to hide in here. Drastically reduces air intake.

good luck.

steviej

Lex3486

Thanks for the quick responses; I may have to try that flashlight thing with the intake hose. In the past however, I've only had noticeable engine problems out of a pipe with large holes, not small ones, but I'll check it out just the same. The air filter is good; newer K&N, so shouldn't be a problem there, and the intake before the filter is fine; I just had it apart a couple weeks ago, so I know it's alright. My guess is either the fuel system or the tranny. Could a clogged filter cause it to hesitate initially like it's doin but not any other time? I've noticed that if you floor it off the line, it does fine really; no problem. It's when you're just drivin normally that the problem occurs. I'll check the fuel situation out tomorrow. I'll let y'all know what I find. Seems like a good idea to replace the filter anyhow; to my knowledge, it's never been changed. I just hope it's not my tranny - $$$ AND time!!! Two things I don't have much to spare!! That's why I bought a Lexus, so my car'd be the last thing I'd have to worry about!! Oh well, I guess that's why it's the RELENTLESS PURSUIT of perfection, b/c they've not actually found perfection yet lol.

Toysrme

Fill the tank up with 93 octane if you can find some, or settle for 91. See if it goes away within a 1/4 of a tank...

lexusk8

If you suspect a fuel delivery problem, do as Toysrme suggested and put in some premium fuel at your next fill-up. Also before your next fill-up, put in some fuel treatment cleaner into the tank. The cleaner fluid will help reduce the clogging of dirt in the gas lines from the tank to the engine, and also the deposit often found at the bottom of the tank. I as well as most of us suggest Techron w/ Concentrate, which is the best in the market. It can be found at any auto parts store (Pep Boys, Autozone, Advance Auto, etc.) for no more than $6. Good luck.

Stefwilli

I had the same problem your having now with my 92 es300. I found out that I was using the wrong grade of gas. I was using 93 grade gas, first I switched to 89, then to 87. I found that the car runs best using 87 grade gas. Try using 87 gas, give it a couple of days(2-3) of using the 87 and you should feel the difference. Also try techtron which is sold at any auto care store. Good Luck.

amf1932

The suggestions that I've read so far about changing the octane grade of fuels make absolutely NO sense to me! The ECU adjusts to changes in octane by automatically changing the ignition timing to work optimally with the grade of fuel within the parameters of what Lexus calls for in these engines, thereby making these suggestions null and void. ALL ES300's are designed to work with either regular grades of fuel(87 Research Method) or high test(93 Research Method). I suggest you re-read what the problem was in the original post!

Lex3486

Well, according to the owners manual, which I take as the final say, 91 or higher octane is reccomended for my car. This is why I always use 93, b/c there is no 91 where I am; only 89 and 93. I will however use some fuel cleaner; I've used it once before in this car and many times in my 92. It's acted perfect for the last 2 days though, so....

amf1932

Your car CAN be used with regular grade of fuel. Don't mix up the terms that are used in your owners manual. 91 Research Method = 87 octane.

steviej

iTrader: (1)

Alan, he may not be mixing up his numbers. The 2002 ES manual also calls for an Octane Ratine of 91(Research Octane Number 96).

steviej

amf1932

This is taken right out of the ES300 2003 Owners Manual.

amf1932

BTW: I switched back to 87 octane fuel 'cause I didn't notice any difference when I used 91 octane fuel. Also, my gasoline mileage did not vary at all. This was done on a trip halfway across the USA in every kind of situation(City & Road driving). Aside from this I saved a few bucks on every fill up.

Stefwilli

I was mainly speaking from experience. This is what I did to solve my hesitation problem. I didn't say that the solution I had needed to be the answer to all hesitation problems. Take it easy when replying to fellow members posts ( ). Oh yeah, it could also be possible that he got some bad gas. My brother has a 96 GS300 handle dgot20's, filled up on regular gas one night. The next day as we were getting on the highway his car cut off and it wouldn't cut back on. Being that his car was certified, lexus came and got the car. When we went to pick the car, lexus told him that he had filled up on bad gas and the ECU shut the car off. So what do you mean by gas grade doesn't matter.

amf1932

When I said regular grade, I meant 87 octane, NOT the quality of the fuel!

In my part of the country regular gas refers only to the octane. Yes, there could have been water mixed with the gas that caused this cutting off of the engine....contaminated gas.

If you look at my above post showing you what a 2003 Lexus calls for, maybe than you'll understand a little better.